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-   -   High engine fan speed in cold weather...a brief story... (http://www.saturnfans.com/forums/showthread.php?t=238597)

pierrot 11-30-2019 09:26 PM

High engine fan speed in cold weather...a brief story...
 
[FONT="Palatino Linotype"][SIZE="3"]Yesterday, I drove a short distance to pick up my son from his friend's house in the early evening, about 5:15 pm, fully dark and rather cold - low 50's (F) and dropping. Driving away from the house I noticed an extra noise from the engine and could tell that the cooling fans were running at a high speed. I next noticed that as I took my foot off of the accelerator pedal and allowed the car to [I][B]decelerate[/B][/I] without braking the RPM would increase and decreases repeatedly between 950 and 1200. However, when braking there was no irregularity. The idle speed RPM in gear was at about 1,000 to1,100 which is high. (Normal idle speed in gear is closer to 800 RPM, IIRC.) The temperature gauge reached to just before the 1/4, or first hash mark from the left. After arriving at this house which is less than two miles from my own, I turned off the engine and waited for my son to come out - approximately 5 minutes. The engine the high fan speed continued for a couple of minutes after we had left, but finally quit and with it the irregular surges while coasting.

This has never happened before. No telltale light illuminated at the dash console, neither engine/SES nor wrench. Without knowing any better, I had a hunch that this might simply be an odd "one-off" kind of thing and so I didn't panic over it. I thought that I'd wait and see if the thing might "correct itself" so to speak. So this morning I went into L A for work and all was normal.......([I]somethin' kinda goofy was goin' on yesterday[/I] :xeye::whoa:).

What do I think was going on? I'm really not sure. My first thought was that perhaps the thermostat seal was allowing antifreeze to bypass the thermostat, but since the temperature gauge showed a fairly normal reading for this type of weather I didn't think it likely. My second thought was that perhaps the throttle position sensor was showing a sign of failure. As I write this, another thought comes to mind - an errant speed sensor. In any event, the car drove quite normally today. We'll see if this kind of event pops up again some time.[/SIZE][/FONT]

02 LW300 12-01-2019 01:12 AM

Re: High engine fan speed in cold weather...a brief story...
 
Do you have a code reader? Some codes will set and not turn on the cel until the second occurrence. Last time I had high fans I had a code but no light for engine taking too long to reach operating temp. The internal rubber seal in the thermostat had started to fail letting coolant flow when it was not supposed to. Purchase the better quality thermostat for better results. I always buy a Stant Superstat in the original temp if available.

pierrot 12-01-2019 02:56 AM

Re: High engine fan speed in cold weather...a brief story...
 
[FONT="Palatino Linotype"][SIZE="3"]Thank you, [B][I][COLOR="blue"]02 LW300[/COLOR][/I][/B], for making the point about when a code will be set. I do have a code reader, happily, but I will certainly be irritated and disappointed if the thermostat has failed since the part was replaced last Summer. I use Stant thermostats regularly and at the OE temp setting. Well, I suppose that I shouldn't complain too much. I've never had a defective thermostat as a problem so one could consider that as being fortunate. I will let folks know how things have turned out after some time has gone by.[/SIZE][/FONT]

pierrot 12-11-2019 02:15 AM

Re: High engine fan speed in cold weather...a brief story...
 
[FONT="Palatino Linotype"][SIZE="3"][U][B]Update[/B][/U]: I was heading to Superior Court for jury service this morning - not too far away. I was stopped at a traffic signal about one mile from my house when I heard the engine cooling fans begin to run at high speed. The temperature was normal for cool weather - just over the first hash mark, or 1/4 - and stable. This event lasted thirty seconds or less and the fans then went quiet. The return drive home was uneventful. This would suggest, however, that some irregularity is present to cause the cooling fans to improperly engage at high speed.

Until this morning the fans had been operating normally apart from the story in the thread starter message. If all goes well tomorrow morning I will have enough time to get my scanner hooked up to the car before I depart for work to see if anything comes up.[/SIZE][/FONT]

02 LW300 12-11-2019 12:28 PM

Re: High engine fan speed in cold weather...a brief story...
 
The temperature indicated on my temperature gauge is very stable. My car warms up to that temp in the first 1/2 mile unless the heater fan is on medium or above. When using the heater on a freezing day the car still warms up in the first mile and a half.

fdryer 12-11-2019 03:39 PM

Re: High engine fan speed in cold weather...a brief story...
 
Would it help to monitor coolant temps with a reader while driving (distracted driving aside)? Before I created a way to hold my tablet with a window suction mount, I laid it down on the console to slide off at random during moderate braking/turning maneuvers. I wanted a larger OBD II display as opposed to popular cellphone apps like Torque. Having eight eyes (think about it) can be an exercise in choosing which part of eyeglasses is right to view a tablet or cellphone display while driving (head bobbing). Frustrating moments occurred while driving and pressing the record tab to save a moment of screen display for later review of parameters. I needed several baseline parameters; cold idle, warm idle, and a few chosen speeds to record parameters above idle rpm. I'm not sure if OBD Wiz has a record mode to allow recording timed events. Perhaps I'll spend some time looking into this feature.

Monitoring coolant temps at several points beginning with cold start, a half mile down the road as mentioned and several other mileage waypoints may reveal something. It would be even more valuable if parameters were captured when cooling fans turned on. This presumes a host of parameters can be captured as a freeze frame or recorded at length for later review.

floridasl22002 12-11-2019 04:23 PM

Re: High engine fan speed in cold weather...a brief story...
 
Pierrot,

Don't know if this link to an earlier thread (2008) is of any use, but covers fans going awol.

[url]http://www.saturnfans.com/forums/showthread.php?t=120310[/url]

pierrot 12-12-2019 03:45 AM

Re: High engine fan speed in cold weather...a brief story...
 
[FONT="Palatino Linotype"][SIZE="3"]Thank you for the link, [B][I][COLOR="blue"]floridasl22002[/COLOR][/I][/B], I appreciate it!

[B][I][COLOR="blue"]fdryer[/COLOR][/I][/B], I would like to be able to directly monitor the engine cooling system's temperature. The scanner I own doesn't have that capability and I don't plan on spending any money for such a thing at this time. My daughter's car is at a Mitsubishi dealership and may require a BCM replacement (although I hope that it won't). They're about the same price as the GM versions we're so familiar with. A large household expense has already hit me this month. Oi vey...

Today I was on the run to get out for work and didn't take the scanner with me which was too bad. [B][U]The event occurred again at about the same time frame and distance from home[/U][/B] this morning. After the event ended there was no further issue for the rest of the day. This time I noticed that it was causing a small increase in the curb idle speed, about 50 RPM or so. We'll see about tomorrow. :eek: As a side note, [B][I][COLOR="blue"]02 LW300[/COLOR][/I][/B]'s vehicle warm up experience mirrors my own. The ECOTEC engines don't take long to reach, or nearly reach, normal operating temperatures.

Candidly, I'm thinking that the problem may stem from a partially failing thermostat seal.[/SIZE][/FONT]

fdryer 12-12-2019 09:53 AM

Re: High engine fan speed in cold weather...a brief story...
 
Perhaps considering a new scanner that can be used on many vehicles? You may have read of Torque apps for cellphones using a Bluetooth adapter (BAFX seems popular around these forums). If I'm not mistaken, Torque comes in two flavors, base setup (free) and more options for a few dollars. There are several YouTube videos to view to see if it meets your needs. These two seem to be a low cost way to have live readouts while driving.

Dsaturn 12-12-2019 11:56 AM

Re: High engine fan speed in cold weather...a brief story...
 
My 2.2 L200 does that when it hits about 40f Getting ready to do a Radiator and Tstat soon. Will report if seal on Tstat is damaged. I can not find the thread on here but do remember reading about this problem on here. If I recall correctly Solution was Change Temp pressure sensor.

pierrot 12-17-2019 12:25 AM

Re: High engine fan speed in cold weather...a brief story...
 
[FONT="Palatino Linotype"][SIZE="3"]So today the engine cooling fans hit high speed again after about a mile of driving and with the coolant temperature just beyond the first hash mark to the right (1/4) followed by a corresponding increase and decrease in the idle speed - up and down with the RPM. Shortly thereafter the fans died down and the idle speed went down to normal, 750 (or so) RPM in gear and no further irregularities for the day.

I had my code reader with me and it found a [B]P0507[/B]: [B]Idle Speed High[/B]. In short, [I][COLOR="blud"]the FSM doesn't describe any[/COLOR] [U][B][COLOR="green"]malfunctioning of the cooling fans[/COLOR][/B][/U] [COLOR="blud"]related to this code[/COLOR][/I]. My hunch is that the code appearing is not the primary problem, but a secondary one driven by the high speed of the cooling fans at a low cooling system temperature. Unlike the abnormal fan behavior, the high idle speed does - in this instance - trigger a DTC to appear.

I should have another FCM here in the garage; the factory original. The current unit in the car was from a donor L-Series car that was younger than mine. I may swap them to see if that changes anything. Nevertheless, I need to do more reading. [/SIZE][/FONT]

fdryer 12-17-2019 01:04 AM

Re: High engine fan speed in cold weather...a brief story...
 
There must be someone you know with a reader to borrow. If I were nearby and not on the Right Coast, you'd have a reader to monitor coolant temps..........and other parameters.

I'm leaning towards an errant t-stat.

pierrot 12-17-2019 01:19 AM

Re: High engine fan speed in cold weather...a brief story...
 
[QUOTE=fdryer;2337247]There must be someone you know with a reader to borrow. If I were nearby and not on the Right Coast, you'd have a reader to monitor coolant temps..........and other parameters.

[B][COLOR="blud"]I'm leaning towards an errant t-stat[/COLOR][/B]. (emphasis by pierrot)[/QUOTE][FONT="Palatino Linotype"][SIZE="3"]Firstly, I need to look into the app you referred to in a previous post and see if it can help. ([I]Oh, BTW, you may be closer to a coast line than I am. My home is about 45 miles away from the nearest oceanfront beach.[/I])

Secondly, I'm more suspicious of a thermostat problem just as you are. I'm thinking more along the lines of fluid bypassing the thermostat seal. The thermostat appears to function normally as the temperature gauge does rise and fall according to ambient temps and driving conditions so I'd be inclined to simply replace the seal. I may happen to have an extra thermostat seal here in the garage as left over parts from the [I][B]Fel-Pro[/B][/I] kit [B][I]ES-71282[/I][/B] (used with water pump replacement). Making time available for that work is another concern...:|[/SIZE][/FONT]

pierrot 12-21-2019 02:24 AM

Re: High engine fan speed in cold weather...a brief story...
 
[QUOTE=pierrot;2337249][FONT="Palatino Linotype"][SIZE="3"]...
Secondly, I'm more suspicious of a thermostat problem just as you are. I'm thinking more along the lines of fluid bypassing the thermostat seal. [COLOR="blud"][B]The thermostat appears to function normally as the temperature gauge does rise and fall according to ambient temps and driving conditions[/B][/COLOR] so I'd be inclined to simply replace the seal...[/SIZE][/FONT][/QUOTE][FONT="Palatino Linotype"][SIZE="3"]As I've continued to drive the car in this odd "estate" it occurred to me that my statement above wasn't as well thought out as I'd supposed. If indeed there is a leak of antifreeze bypassing the thermostat seal within the water outlet (thermostat housing) then regardless of the size of the leak, that leak would continue. This would then contradict my highlighted statement above. Such a leak mean that the engine temperature should [U]tend to be lower than average overall[/U] throughout the course of any trip taken. With that in mind, I now believe it is an electrical problem. The [U][I]more likely[/I][/U] source of trouble here appears to be the [B][U][COLOR="blue"]I[/COLOR][/U][/B]dle [B][U][COLOR="blue"]A[/COLOR][/U][/B]ir [B][U][COLOR="blue"]C[/COLOR][/U][/B]ontrol (IAC) Valve. It needs to be tested and will be tomorrow.[/SIZE][/FONT]

pierrot 12-21-2019 01:14 PM

Re: High engine fan speed in cold weather...a brief story...
 
[QUOTE=pierrot;2337839][FONT="Palatino Linotype"][SIZE="3"]...The [U][I]more likely[/I][/U] source of trouble here appears to be the [B][U][COLOR="blue"]I[/COLOR][/U][/B]dle [B][U][COLOR="blue"]A[/COLOR][/U][/B]ir [B][U][COLOR="blue"]C[/COLOR][/U][/B]ontrol (IAC) Valve. It needs to be tested and will be tomorrow.[/SIZE][/FONT][/QUOTE][FONT="Palatino Linotype"][SIZE="3"]My problem is an intermittent one and there is no doubt that the problem still exists. Yesterday's drive yielded no DTCs - [I]this has also occurred on other occasions as well[/I] - although the engine idle did take somewhat longer than normal to settle into proper curb idle in gear at 750 RPM. Intermittent problems lead to the following checks in the FSM: resistance at the IAC valve contacts and throttle linkage inspection.

The FSM states that resistance between terminals A & B and C & D should be from 30 to 60 ohms. I measured both pairs at 45 ohms which seems to be as good as it could get. I would like to note that there is no letter designation on the valve whatsoever so as to know exactly which contacts are A, B, C, or D. So I simply went with each pair of contacts from left to right and that turned out to be the arrangement. No other pairings yielded a reading.

The next check was to inspect the throttle position screw for signs of tampering and linkage for wear (all of which is in the same small area). As far as I could tell the linkage seems fine and the throttle stop screw has never been touched by me or anyone else since I've owned the car. So thus far I'm still in a quandary; do I take the leap and simply replace the IAC vavle or do I replace a thermostat seal which I believe to be okay just to eliminate that as a possible cause for this issue? [B][I][COLOR="blud"]Is it conceivable that a resistance problem with the IAC valve is only apparent at the time of the irregularly high idle speed?[/COLOR][/I][/B] [B][I][COLOR="green"]The more I think about that, the answer could be yes. We have learned from others, notably [B][I][COLOR="blue"]fdryer[/COLOR][/I][/B], about resistance issues related to intermittent CKP sensor failures[/COLOR][/I]. (I know others here like to call it the CPS. I prefer the factory's designation.)[/B][I] If I replace the IAC valve then I must remove the throttle body as there isn't adequate space to get a Torx T20 bit onto the lower attaching screw head. It also looks like a throttle body cleaning would be worth while. Of course, I'd need to get a throttle body base gasket as well.[/I]

Oi vey...more time to set aside for this...:|[/SIZE][/FONT]

fdryer 12-21-2019 03:35 PM

Re: High engine fan speed in cold weather...a brief story...
 
There are some symptoms of a faulty iacv that may or may not be obvious. One is if it sticks in one position. The iacv is supposed to extend and retract from pcm commands to alter idle rpm during all phases of engine running from cold engine startup, warm engine, high electrical loads and deceleration when throttle is released. I think the best way, presuming a normally running engine, to observe iacv action is during a cold engine startup.

With EFI systems no longer needing a choke mechanism to force a rich fuel mixture and cam action to raise idle rpm during cold engine startup on carburetors, the EFI system uses every sensor to automatically adjust rpm and fuel mixtures at every phase of engine running. At cold engine startup, two things occur; rich fuel mixtures as determined by the engine coolant sensor and running a higher than normal idle via the iacv. As we all know, EFI systems do not require anyone to depress the gas pedal at startup as the EFI system knows what to do. Since every cold engine needs a richer fuel mixture, the rich mixture can lower idle rpm so the pcm commands the iacv to retract to allow more air thru the bypass air port without disturbing the throttle plate. More air and richer fuel for cold engine starting results in a high idle. From here and some patience, anyone can observe iacv control by simply sitting in place as the engine warms up.

With a cold idle around 1200-1500 rpm, observe the next few minutes as the idle begins lowering automatically in proportion to coolant warming up. Within a few minutes, depending on outside temperatures, high idling should begin dropping within one or two minutes of starting. If sitting longer, the varying idle rpm will continue to drop as engine coolant warms up. During this sitting (not noticed when most of us startup and drive almost immediately) the fuel mixtures are being leaned the more the engine runs. Both fuel and idle are lowering automatically by pcm control. The changing idle is a direct result of the pcm continually monitoring every sensor then adjusting the iacv until normal idle is achieved whether driving or letting the engine warm-up in place. The change in idle rpm is the iacv changing from retracted (more air) to extended (less air) thru the bypass air port. On my L300 when starting in 9F temps recently, I spent a few minutes brushing off snow from windows. Within two or three minutes the high idle (1500?) dropped immediately to around 1k rpm before I drove. As coolant temps warmed up, idle continued to drop until it reached 650 rpm, normal idle. My electric throttle doesn't have the iacv so the ecm commands throttle opening automatically. Nevertheless, whether having an iacv or drive by wire throttle, the EFI system controls idle speed.

If you sit and observe high idle changing to a lower rpm the longer you sit with a cold engine, you should see this rpm change without touching the pedal. If you see idle speed changes, you're observing the iacv modulating engine rpm as the pcm deems necessary. The corollary is with a faulty iacv with idle not changing or remaining at one rpm level outside where its expected to be.

pierrot 12-21-2019 04:33 PM

Re: High engine fan speed in cold weather...a brief story...
 
[FONT="Palatino Linotype"][SIZE="3"]A fabulous explanation, my friend! I began to understand this as I was reading up on the P0507 trouble code and following the diagnostic trouble tree. It's really fascinating how all of this works. Looking further into the FSM regarding the throttle body and where to find the throttle stop screw I also discovered the possibility of having a worn seal at the IACV. As one might expect, it stated that if such was found that the valve has to be replaced. At that point I really wanted to be able to remove the valve for inspection and that's when I discovered that I'd need to remove the throttle body in order to do so. [I]BTW, the FSM states that the throttle body base gasket is reusable provided that it hasn't been damaged and that's just fine with me. The problem there is that the condition of the base gasket is unknowable until it can be seen. :( On a positive note, the gasket is actually a rubber/silicone seal so it can have more longevity to it and I replaced it once several years ago so it's not the factory original.[/I][/SIZE][/FONT]

fdryer 12-21-2019 05:14 PM

Re: High engine fan speed in cold weather...a brief story...
 
I too found several gaskets of silicone or similar synthetic material where I didn't have to order them. They're reusable because of their synthetic nature to outlast paper gaskets. This occurred for my timing cover, all three intake manifolds pieces, an intermediate manifold and other parts when replacing the t-stat. Much less delays in finding out a gasket is torn, ordering and waiting for it to finish repairs.

Although my L300 doesn't have a iacv, reading other forums where it is used tends to make me conclude they're reliable with few problems and are mostly maintenance free. Similar to egr valves. At 108k miles, I have not seen an error code for my egr valve and the engine is running as smooth as it was when it left the factory. One key factor may be using M1 oil for most of its life, even using extended oil change intervals. One issue that may affect iacvs depends on the amount of pcv blowby gases that are recycled back into the intake air system. Crankcase ventilation requires all combustion blowby gases recycled back to the intake system. This is where anyone removing their throttle bodies discovers it caked in dark goo and find their entire intake manifold covered in it. Technically, it does no harm since the engine doesn't care and has been running this way since the vehicle left the factory. Some spend the time removing and cleaning it but forget or ignore the fact that as soon the the engine is started up the crankcase gases continues to coat the interior of intake manifolds and throttle body interior with blowby products. The engine doesn't care and runs fine.

pierrot 12-27-2019 01:26 AM

Re: High engine fan speed in cold weather...a brief story...
 
[FONT="Palatino Linotype"][SIZE="3"]Today, for the first time ever, the [I][B][COLOR="blud"]SES[/COLOR][/B][/I] telltale warning lamp appeared while driving. The same P0507 DTC was read by the scanner with no other codes present. I think the PCM is "angry" at me :upset: :hothead: for not working on the problem. :whoa: For the first time in my life my car is beginning to scare me!! :eek::eek: At least I've got what I need to do the work - the IAC valve and a can of throttle body spray cleaner. Our true winter weather is making it difficult to get the work done. I saw snow on the foothills close by. It seems that last night our snow level dropped to something near 2K feet in elevation. I've not seen snow so near to our home since we moved to this city in 2003! I have to keep the house heater on quite a bit lately.[/SIZE][/FONT]

pierrot 12-30-2019 08:54 PM

Re: High engine fan speed in cold weather...a brief story...
 
[FONT="Palatino Linotype"][SIZE="3"]Regardless of our colder weather this Winter, some work on the car has been done. I took off the throttle body late Saturday afternoon to clean it and then replace the IAC valve. The upper end of the throttle body was a bit on the oily side (dirtier than I'd anticipated) and, clearly, the throttle body intake is drawing in [U]some[/U] "blow-by" from the PCV system. First up - before the cleaning - I removed the IAC valve. The pintle had a significant amount of oily soot built up on it and it lead me to think that perhaps the part isn't bad at all. I set it aside and cleaned the throttle body throat and IAC valve air passage. (The throat is nice and shiny!) Considering the possibility the the intermittent code appearance was resulting from the soot build up on the IAC valve pintle ([I]perhaps causing [U]improper[/U] pintle movement, whether retracting or extending out from the valve housing[/I]), I cleaned it and the o-ring seal, and reinstalled the unit. From Sunday until now, late Monday afternoon, there is no P0507 code present. I will keep a watch on this, of course, and if the code returns I will install the replacement valve which I'd purchased.

(If all goes well, I'll be able to return the new valve to AutoZone.)[/SIZE][/FONT]

pierrot 01-04-2020 12:52 AM

Re: High engine fan speed in cold weather...a brief story...
 
see next message

pierrot 01-04-2020 12:53 AM

Re: High engine fan speed in cold weather...a brief story...
 
[FONT="Palatino Linotype"]Well, I wasn't as lucky as I'd hoped I might be. The P0507 came back so I replaced the IACV yesterday. I decided not to clear the DTCs after installing the IACV. It immediately turned off the SES telltale lamp, but the code remains in the memory. I've put on about 145 miles since installing it and I'm waiting/[U]HOPING[/U] :| for the PCM to cancel out the code. The idle is functioning normally and there has actually been a performance improvement.

I discovered a wonderful thing after cleaning the throttle body. The accelerator pedal response improved significantly! :yes: I was beginning to believe that perhaps the engine was "showing its age" for some weeks now. But a freshly cleaned throttle body has turned that idea around. For now, the car has more power at 324K miles than it 323K miles! :D[/FONT]

pierrot 01-07-2020 12:37 AM

Re: High engine fan speed in cold weather...a brief story...
 
[FONT="Palatino Linotype"][SIZE="3"]Yesterday, while driving on the freeway I noticed an odd deceleration issue after only a couple of miles. When I'd take my foot off of the accelerator pedal to depress the brake pedal I'd get a [U][B]slight[/B][/U] "kick" [B][I][COLOR="blud"]as if[/COLOR][/I][/B] the transmission were trying to down shift. ([I]I began to think that perhaps one of the solenoids on the valve body was giving me trouble.[/I]) Later, I noticed that when using the cruise control it would not hold its setting at all and I'd never had any problems with the cruise control up to that moment. Eventually I noticed some fluctuation of the RPM gauge which suggested that something was amiss there again.

Sure enough, I had the following: 1) a freeze frame and, 2) pending P0507 DTC [U]with no SES lamp illumination[/U]. Eventually the event subsided and all went back to normal - no odd "kick" from the transmission when decelerating and the cruise control function was fully restored. This is the first time that this sort of thing has occurred when at higher speed and RPM. So for now, I will wait through some more cycles to see if the DTC clears or remains. Sadly, since this is an intermittent problem the FSM has very little to say and I've replaced the only item it suggests as a culprit within the fuel system. Today's drive for work was uneventful, normal.

With regard to the cruise control operation shutting down while this event was ongoing I take it to mean this: that since the PCM could not verify proper control of the engine RPM and speed it would not allow the cruise control system to take over control of the throttle. This appears to be a built-in "fail-safe" feature.[/SIZE][/FONT]

Dsaturn 01-07-2020 06:51 AM

Re: High engine fan speed in cold weather...a brief story...
 
I had a similar problem when I bought my car. It turned out to be the speed sensor. on the back side of the trans passenger side. Mine never threw a code, just put me in loop mode so car would only do 10 mph.
FSM should have specs to test that.

fdryer 01-07-2020 05:08 PM

Re: High engine fan speed in cold weather...a brief story...
 
[QUOTE=pierrot;2338555][FONT="Palatino Linotype"][SIZE="3"] .... With regard to the cruise control operation shutting down while this event was ongoing I take it to mean this: that since the PCM could not verify proper control of the engine RPM and speed it would not allow the cruise control system to take over control of the throttle. This appears to be a built-in "fail-safe" feature.[/SIZE][/FONT][/QUOTE]

If you have service manuals, they describe in long hand what you imagined, the software engineers worked with the EFI system group (if they're in different departments) to develop the [I]smart[/I] computer. you just described the [I]smart[/I] part of the ecm/pcm - preventing or disconnecting cruise control when a parameter isn't met to prevent any chance of a runaway condition or unintended circumstances from allowing cc to run. There's a list of parameters cc programming uses before its allowed to set and when set, disconnects when one of the parameters isn't met, a requirement to allow cc to operate. When I lost the electronic library, I can't copy, paste or reprint part or whole files to reiterate the list of parameters before cc is allowed or disconnects when in use. If you understand flow charts, electronic computer systems uses a similar flow chart with every conceivable question asked long before a program is created to ensure every possible situation is asked with a yes/no answer to rule out every situation. The US space program is based on this simple yet complicated premise of developing flow charts to ensure accurate monitoring of every parameter before a launch can occur and in the expected sequence leading up to a launch. Unfortunately, all the mice and men cannot predict every situation that led to the Challenger and Apollo 13 disaster. The [I]smart[/I] computer is a direct result of smart people gathering together to develop and refine computers to what we have today.

The [I]smart[/I] part of computers insofar as cc use goes beyond just monitoring set speed and adjusting as loads increase/decrease to slow/accelerate a vehicle's set speed. Since electronics governs much of our vehicles, taking full advantage of incorporating more data into determining whether or not cc is allowed or not brings more meaning to safer driving most of us aren't aware of. Set it and steer as all we want for cc effectiveness. The hidden goings on in electronics is being monitored so if anything doesn't meet cc programming, its defeated. Some may think its a failure of cc when, as you discovered, isn't allowed when one parameter fails in the list of parameters. Safety. No different from abs; before abs we were allowed to lock up brakes and skid to either a stop or crash but with abs it won't allow brakes to lock and give drivers the option to steer away from an impending crash or crash into something else.......with the last possibility of actually braking to a safe and complete stop without damage. If abs fails internal self checks (ongoing as long as ignition is ON and car moving) it automatically disables itself to prevent interfering with braking as it was before abs - locking up brakes when panic braking occurs. Smart engineering in one form or another.

pierrot 01-08-2020 02:09 AM

Re: High engine fan speed in cold weather...a brief story...
 
[FONT="Palatino Linotype"][SIZE="3"]Well, Master Freddy - [I]I know it's [B][COLOR="blue"]fdryer[/COLOR][/B], but I'm having fun here since we had a weekend of watching the Lord of the Rings movie trilogy[/I] - I have to say that my idea about the cruise control operation being disengaged by the PCM came about by reading other posts you'd created here in SaturnFans. It's helped me to think about how that computer is "thinking."

BTW, what's [B]VCX NANO[/B]?[/SIZE][/FONT]

pierrot 01-08-2020 02:14 AM

Re: High engine fan speed in cold weather...a brief story...
 
[QUOTE=Dsaturn;2338564]I had a similar problem when I bought my car. It turned out to be the speed sensor...[/QUOTE][FONT="Palatino Linotype"][SIZE="3"]It's an interesting thought to consider. The trouble tree in the FSM makes no mention of the speed sensor in the course of the diagnosis and what it may lead to, but who knows? Perhaps an error with that part could have an impact on my issue...[/SIZE][/FONT]

pierrot 01-09-2020 03:03 PM

Re: High engine fan speed in cold weather...a brief story...
 
3 Attachment(s)
[FONT="Palatino Linotype"][SIZE="3"]One thing thus far is certain...the code won't go away. I was able to get information from Innova by hooking up the scanner to my laptop, connecting it to a program on their website and received detailed information on the failure. One surprise to me is the low temperature at which the DTC P0507 occurs. See the pages attached.[/SIZE][/FONT]

fdryer 01-09-2020 05:49 PM

Re: High engine fan speed in cold weather...a brief story...
 
Was this data taken with a cold or warm engine? Can this Innova reader display cookant temps? When the error occurs, the OBD II system automatically takes a snapshot at the moment the error code is generated, known as freeze frame since signals from every sensor changes dynamically. Sometimes it's difficult to know if the error occurred with a cold engine, during warm-up or after reaching operating temps and may be temperature related. If P0507 it's coolant temperature related, what if the coolant sensor or thermostat becomes faulty. An errant sensor or t-stat can skew program monitoring to create a false error code. The coolant sensor has never been found faulty in the L-series but t-stats do fail. I'm wondering if your t-stat failed and running colder than normal.

02 LW300 01-10-2020 01:53 AM

Re: High engine fan speed in cold weather...a brief story...
 
2 Attachment(s)
This is from my 2002 fsm.

pierrot 01-10-2020 04:11 AM

Re: High engine fan speed in cold weather...a brief story...
 
[QUOTE=fdryer;2338821]Was this data taken with a cold or warm engine?[/QUOTE][FONT="Palatino Linotype"][SIZE="3"]Although the time stamp on the first page is at 2:19 am ([I]I fast asleep at that time![/I]) for 01/09, the last time that this code was read and had and SES lamp on was yesterday evening, 01/08, 8:19 pm. The engine was still cold and when the freeze frame "locked" in place it obviously occurred before the vehicle was moving as no vehicle speed was recorded. Evening temps here locally are chilly for us - in the mid-40's.

[QUOTE=fdryer;2338821]Can this Innova reader display coolant temps?[/QUOTE]No, it cannot. It merely displays the codes and the active emission areas which the PCM is monitoring. Looking at the pages of the report one can see that there are several monitors altogether which do not exist in this car's PCM (wherever "[U]not supported[/U]" is found in the report).

[QUOTE=fdryer;2338821] When the error occurs, the OBD II system automatically takes a snapshot at the moment the error code is generated, known as freeze frame since signals from every sensor changes dynamically. Sometimes it's difficult to know if the error occurred with a cold engine, during warm-up or after reaching operating temps and may be temperature related. If P0507 it's coolant temperature related, what if the coolant sensor or thermostat becomes faulty. An errant sensor or t-stat can skew program monitoring to create a false error code. The coolant sensor has never been found faulty in the L-series but t-stats do fail. I'm wondering if your t-stat failed and running colder than normal.[/QUOTE]Your remark about the coolant temperature made me realize that it wasn't so strange after all to see a low digital reading of it and so I'm happy that you brought attention to it. The time it took for the high engine idle speed to drop down to normal was about four minutes. The idea about a thermostat bearing some relation to this problem has not totally left my thoughts although I find it a vexing idea. Lately, the temperature gauge reading is just to the right of the first hash mark (about "5/16" instead of the more common 3/8 position) so it's slightly lower than normal, but that would also agree with our cooler daytime ambient temps. Further, as I watch the temperature gauge at the dash there is normal fluctuation present, both higher and lower, depending on the time of day and the traffic conditions I find myself in.

Previous reports of thermostats being stuck open (how ever much), or thermostat seals leaking - and thus allowing the antifreeze to move too swiftly through the cooling system - don't seem to apply here because there are common symptoms which aren't present in my situation: the cooling system fans run much longer and more often, and the temperature gauge reading is also below what I am seeing at the dash console. Thus I cannot logically justify a thermostat related failure as a contributing factor in the appearance of the P0507 DTC. Since that is my view presently, the matter of replacing the thermostat and seal - or the seal only - is more like an extra-curricular activity than a required pursuit. The vexing part is that there is this lingering question mark about my idea here any way. :|:xeye::xeye:

As an experiment, today I decided to clear the DTC from the PCM's memory. I'm curious as to how long it may take for the code to reappear.[/SIZE][/FONT]

pierrot 01-10-2020 04:23 AM

Re: High engine fan speed in cold weather...a brief story...
 
[FONT="Palatino Linotype"][SIZE="3"]Thank you, [B][I][COLOR="blue"]02 LW300[/COLOR][/I][/B]. Your FSM and mine read the same way. It's comforting to know some things didn't change...but I can't deny that it makes me wish I had a Tech II or Tech III Scan Tool. :ugh:[/SIZE][/FONT]

fdryer 01-10-2020 04:28 PM

Re: High engine fan speed in cold weather...a brief story...
 
As a general rule about thermostats, the engine doesn't care about ambient temperatures with the exception of starting up to allow the EFI system in determining fuel mixtures. Cold engine starting requires extra fuel as cold air and cold coolant informs the engine computer. The computer then determines fuel mixtures. Under normal conditions, once engine operating temperatures are reached, via its t-stat, the temperature needle doesn't vary. While outside temps can vary from -20F to 125F, the temperature gauge needle should never move since the t-stat is governing overall coolant temps for the engine for optimum emissions and performance. I suspect your t-stat is worn because you notice the temperature needle moving in relatively tepid ambient temperatures. More members with L200s can offer they're temperature gauge observations, including summer and winter values and whether or not their temperature needles move as much as yours does. While not a L200, any vehicle will display the same unwavering temperature needle sitting in one place once operating temps are reached with a good t-stat. A reader displaying coolant temps is the best way to observe it in every temperature condition.

My L300 always shows the needle around the 11 o' clock position whether in freezing NYC winters or hot and humid summers with ac running. All t-stats regulate coolant temps regardless of outside temps. My reader shows between 188F to 200F with the temperature needle sitting in one place. The temperature gauge is only as precise as necessary - letting us know the engine's cold, running fine or overheating. Before EFI systems, this was fine but once EFI systems became complicated with emissions and tighter emissions standards to reduce pollution as much as possible, analog temperature displays are still used for general info until errors related to coolant temps rears its ugly side. P0128 is an easy error code but some may misinterpret the coolant sensor as the fault when the t-stat is more likely to fail. P0507 is about high idling with several things affecting an errant and random high idle. This error code points in a general direction and diagnosing where the fault lies can be difficult.

pierrot 01-11-2020 07:04 PM

Re: High engine fan speed in cold weather...a brief story...
 
[FONT="Palatino Linotype"][SIZE="3"]You are, of course, correct about the thermostat's working as not being influenced by ambient temperatures. However, my temperature gauge does show differences related to that and how fast I'm traveling. For example, today as I was returning from Downtown L A driving at normal freeway speeds the temp gauge was holding at "5/16." The outside temperature was at 61 degrees F according to the Google weather app. As I transitioned to another freeway and traffic slowed to below 15 mph I watched the temperature gauge level rise to nearly "3/8." After that patch of slowness ended and I was once again traveling at normal freeway speeds the temperature gauge dropped back down to 5/16. If I'd been sitting in slow traffic longer the gauge could've risen to the half way mark as I'd seen it do earlier this week, this past Monday. Conversely, when my car had its only encounter with cold, winter weather in the San Bernardino Mts. the temperature gauge barely made it to the 1/4 (first mark to the right of "cold") after five minutes of sitting and warming up. It remained at that temperature level until it was at lower elevations where ambient temps were higher.

[U]Other interesting events[/U]: while driving to work yesterday morning the P0507 DTC reappeared...(great :hmpf:). After that event I was ready to get myself a replacement thermostat and expect to install it this weekend. Yesterday evening while driving home I plugged in the scanner and it read, "[B][I][COLOR="blud"]nodtc[/COLOR][/I][/B]." Now here was a major surprise! The scanner was flashing an [I][U]EV[/U][/I] symbol which meant that there was an incomplete internal diagnostic of the EVAP system. This morning I plugged in the scanner and had the same result except that the EV symbol was [U]not[/U] flashing, meaning that all monitored elements were functioning within normal parameters. Since all was working within normal parameters ([I]at least for today[/I]) it suggests that the engine had reached the required operational temperature. While this is good news, I'm not yet ready to say that this problem has been corrected.[/SIZE][/FONT]

fdryer 01-11-2020 10:23 PM

Re: High engine fan speed in cold weather...a brief story...
 
I think you're using the new term 'confirmation bias' to correlate the wandering temperature gauge needle with assumptions of correct t-stat operation. I disagree. The t-stat regulates coolant temps regardless of ambient temps as I stated previously in freezing temps, hot and humid weather with ac running or tepid temps idling in traffic or running way past the speed limit as police are giving chase. The t-stat simply regulates liquid coolant. I believe you're seeing the temperature needle moving around due to the worn t-stat opening sooner than its rated designation so you're seeing the needle move as airflow thru the radiator stops or flows when the car stops or moves. The temperature gauge needle should not move once the cooling system reaches operating temperatures. A worn t-stat is easily seen with a reader capable of displaying actual coolant temps as the ecm/pcm sees it with a digital display for an immediate visual indication. I don't know any other way to convince you to use a reader to display actual coolant temps as regulated by either a functioning or malfunctioning t-stat.

Do you have Autozone, Advance Auto or other auto store allowing free readings with their OBD II readers? It would take less than a minute to plug in a reader, scroll thru the menu and select live parameters to display coolant temps. Presuming you know what the rated t-stat temperature for your L200, either the correct temperature is displayed or not against stock t-stat value.

02 LW300 01-11-2020 11:06 PM

Re: High engine fan speed in cold weather...a brief story...
 
Our 2.2 temp is 180. My needle is rock solid after about 2 miles of operation year round. There is an internal rubber seal in the thermostat that lets coolant flow as it fails irregardless of the temperature control part of the thermostat.

pierrot 01-12-2020 01:25 AM

Re: High engine fan speed in cold weather...a brief story...
 
[FONT="Palatino Linotype"][SIZE="3"]Confirmation Bias...sure, that's a fair description. As I said at the end of my last post, [B][I][COLOR="green"]I'm not yet ready to say that this problem has been corrected[/COLOR][/I][/B]. The upshot of that is this - if the code appears again I will go after replacing the thermostat. [B][I][I][COLOR="blue"]fdryer[/COLOR][/I][/I][/B] and [B][I][COLOR="blue"]02 LW300[/COLOR][/I][/B], I appreciate your continued contact and replies here. Mille grazie!![/SIZE][/FONT]

pierrot 01-13-2020 04:10 AM

Re: High engine fan speed in cold weather...a brief story...
 
[FONT="Palatino Linotype"][SIZE="3"]So I've replaced the thermostat. I also performed a "post mortem" on the thermostat I removed by placing it in preheated water at the stove. I used my Universal brand thermometer to verify the water temperature. The thermostat opened correctly at 180 degrees F. While the poppet was opened I was able to examine its seal. The poppet seal showed no apparent damage or weakness. The same could not be said, however, of the thermostat seal. It felt somewhat squishy and didn't feel tight enough on the thermostat's flange edge. More to come...[/SIZE][/FONT]

pierrot 01-14-2020 08:49 PM

Re: High engine fan speed in cold weather...a brief story...
 
[FONT="Palatino Linotype"][SIZE="3"]We now return with another episode of [B][I][COLOR="green"]As the Trouble Code Turns[/COLOR][/I][/B]...

When last we'd heard from the intrepid LS1 a new thermostat was installed. The next morning within a mile of leaving its comfortable garage the cooling system fans began to run at high speed...uh oh! :eek: The owner did not have the code reader in the car so information couldn't be retrieved. The incident was not long lasting and the rest of the day passed as if nothing had happened.

The next morning - today - the LS1 ran normally. The code reader was brought along and plugged in. It displayed this - [B][I][COLOR="blud"]nodtc[/COLOR][/I][/B]. The owner noticed that the coolant temperature gauge was at a "base" position slightly higher than it had been with the other thermostat since yesterday (regardless of the high fan speeds showing up) though not at 3/8. It tends to hold that position unless the car is being driven in slow traffic when it will show an increase in temperature even up to the middle hash mark.

But while the owner continues his vigil what will happen next? Will the idle speed RPM run high and too long beyond the expected parameters once again as it had previously? Will the PCM share an alert? Will the cooling system fans erupt at high speed, or will days pass by without incident? Stay tuned for the next episode of [B][I][COLOR="green"]As the Trouble Code Turns[/COLOR]![/I][/B][/SIZE][/FONT]

02 LW300 01-15-2020 01:26 AM

Re: High engine fan speed in cold weather...a brief story...
 
Like sand through an hour glass so are the days of our lives. ....

Chaz9496 01-18-2020 06:50 PM

Re: High engine fan speed in cold weather...a brief story...
 
Well, one of those still exists on the T.V. airwaves. Anyway, I've been having Fan Issues again. I was driving out of town last weekend and came to a light after I got there and heard something, so I had to turn down the radio. Low and behold, the fans were running at high speed, AGAIN. It was 8 degrees out and the idle was slightly higher but not drastic. I would assume from the fans running is why. The last time the fans were on full speed the knock sensor wire was broken on the connector. I reset the codes and "Yee,Haw" they stayed off. I was told by a tech that any voltage issues will tell the computer there's a problem and run the fans. Welp, now back to the problem again. The T-Stat was replaced 3 months ago. It was roughly 5 years old. I just did it for my own reference due to the time it was replaced last. I was sitting at a Hardee's parking lot eating and the engine almost stalled but came back to life. I unplugged the fans and headed back home as fast as I could, w/out speeding. I thought it may stall out going home 45 miles away and my friend with a truck was in rehab so I had no ride or way to tow it home if it would stall and not start again. This has happened before but with the fans off. I have no idea what causes the engine to do that, I've had others that have done that as well, it's probably common. Anyway continuing on, the temp gauge was under 1/4 and heat starting to fail slightly on the way there, so something didn't look right. The fans were cooling it in the 8 degree weather. Well, that would do it. Now finding the problem for the second time this issue's plagued me. I read the Idle Speed sensor can cause this. Not sure of the problem yet. I may have to have my (Non-Do It Myself) tech check into his If I can't find it this time. I've had the fans run like this, then stay off on it's own before. Hopefully this is going to be this time.

pierrot 01-18-2020 11:18 PM

Re: High engine fan speed in cold weather...a brief story...
 
[QUOTE=Chaz9496;2339370]...I read the Idle Speed sensor can cause this. Not sure of the problem yet.[/QUOTE][FONT="Palatino Linotype"][SIZE="3"]To be clear, there is no [U][B][COLOR="blud"]Idle[/COLOR][/B][/U] Speed Sensor. There is an [U]Idle Air Control Valve[/U] which has a direct impact on the change in idle speed; from a cold start up until the cooling system has warmed enough to allow a steady decrease of the engine idle RPM until it reaches the correct curb idle RPM.

[QUOTE=Chaz9496;2339370]I may have to have my (Non-Do It Myself) tech check into his If I can't find it this time. I've had the fans run like this, then stay off on it's own before. Hopefully this is going to be this time.[/QUOTE]I hope that it's so for you as well!

When last we met with our indefatigable four-wheeled friend on [B][I][COLOR="green"]As the Trouble Code Turns[/COLOR][/I][/B] the nuisance code was gone. However, the day after that last post P0507 appeared again without the appearance of the SES warning lamp. While the engine idle was below 1000 RPM it was still too high and had remained there for too long after having been started. Now, for three days the code hasn't appeared although I expect that it will in due course.

With that in mind, and not wanting to be [I][B]redundant[/B][/I] about the symptoms I've regularly seen, I don't [I]expect[/I] to post anything further here until this issue is resolved. At this point I'm not sure what my next step, or steps, will be. I do know that I have little interest in simply installing new parts which can be related to this problem, but not lead to resolving it.

I appreciate all of the input provided by other members here in this thread. You have helped me![/SIZE][/FONT]

Chaz9496 01-19-2020 11:40 PM

Re: High engine fan speed in cold weather...a brief story...
 
[QUOTE=pierrot;2339377][FONT="Palatino Linotype"][SIZE="3"] At this point I'm not sure what my next step, or steps, will be. I do know that I have little interest in simply installing new parts which can be related to this problem, but not lead to resolving it.[/QUOTE] I can relate to that. That's just throwing money at it to resolve a problem that's not known what the issue is until it's properly diagnosed. I've done that before and it's a waste of time and $$$ as well. Today I noticed that the heat only got hot when it was idling at a stop light or S-Sign and gets cooler again as you start going. The temp will go up in between 1/4 and 1/2 when it get's hot, then drops to 1/4 when your moving again. It's been barely above 10 degrees most of the weekend and parts of last week but the gauge never did fluctuate like it is now before. I did change the T-Stat a few months ago, which I might have mentioned already in this same topic. I didn't replace the seal but since the T-Stat was replaced this is when it seemed to fluctuate in temperature. I still have the old stat in the garage that I may put back in WITH a new seal and see what happens. I suspect possibly the coolant may be leaking past the seal since it was never replaced this time, or a Clog or Air Pocket in the system. From what I read in the Chilton's manual, I thought the coolant tank was Self Bled and wasn't needed with this type of system, others makes needing to run with the cap off as you do when I owned cars with capped radiators and tanks. I could hear air bubbling when I was refilling it, so I assumed it was bleeding itself. I know nothing about how the "Non-Capped" radiator system works refilling it. I don't remember ever doing it before when changing it and it worked fine. Any thoughts will be helpful if I'm reading that incorrectly.

Dsaturn 01-22-2020 08:25 AM

Re: High engine fan speed in cold weather...a brief story...
 
What kind of T stat did you use? I have run into a lot of problems with cheap stats. Either go with OEM GM (very expensive) or a stant super stat mid range in price. Never use those fail safe stats. Also why wouldn't you replace the seal why you had it apart?

Chaz9496 01-22-2020 08:59 AM

Re: High engine fan speed in cold weather...a brief story...
 
Murray T-Stat because I work at O'Reillys due to the fact I'm coasting to retirement so to speak. lol. I get it close to 1/2 off. I asked a tech about it that I deliver to and he said, That's probably it, I used a Murray. lol. He may be right, I didnt change the seal because i did when I replaced it in the other engine in 2013 and it didnt look bad in any way. I'm going to change it back to the old one that looked still new and with a new seal and see what I get from there, it may not have needed changed at all in the first place, at least it had heat at that time.

Dsaturn 01-22-2020 09:38 AM

Re: High engine fan speed in cold weather...a brief story...
 
I see they are $6 bucks. I would never put a cheap Tstat like that in my car. Sometimes going cheap can cost a lot more in the long run. I paid $16 for my Super stat at local store but now Rock auto has them back in stock for $9. :x

lrbraner 01-22-2020 11:03 AM

Re: High engine fan speed in cold weather...a brief story...
 
[QUOTE=Dsaturn;2340697]What kind of T stat did you use? I have run into a lot of problems with cheap stats. Either go with OEM GM (very expensive) or a stant super stat mid range in price. Never use those fail safe stats. Also why wouldn't you replace the seal why you had it apart?[/QUOTE]

Have you had problems with the fail safe thermostats ?

Chaz9496 01-22-2020 11:04 AM

Re: High engine fan speed in cold weather...a brief story...
 
$6 ? mine was 13 at my cost for the Murray. The one I had in it was a Duralast from Autozone. It worked fine to me. I jist changed it out because it was going on 7 years since I replaced it, that was when my Mom owned it. She gave it to my Son in 2015. The trans went out in it, so I put the engine in my 2001 because it only had 95K miles on it and nine was smoking at 200K. I know that doesnt have anything to do with the topic but just sayin'.

fdryer 01-22-2020 03:20 PM

Re: High engine fan speed in cold weather...a brief story...
 
2 Attachment(s)
[QUOTE=Chaz9496;2340167] ......Today I noticed that the heat only got hot when it was idling at a stop light or S-Sign and gets cooler again as you start going. The temp will go up in between 1/4 and 1/2 when it get's hot, then drops to 1/4 when your moving again. It's been barely above 10 degrees most of the weekend and parts of last week but the gauge never did fluctuate like it is now....... I did change the T-Stat a few months ago, which I might have mentioned already in this same topic. I didn't replace the seal but since the T-Stat was replaced this is when it seemed to fluctuate in temperature. I still have the old stat in the garage that I may put back in WITH a new seal and see what happens. I suspect possibly the coolant may be leaking past the seal since it was never replaced this time, or a Clog or Air Pocket in the system. From what I read in the Chilton's manual, I thought the coolant tank was Self Bled and wasn't needed with this type of system, others makes needing to run with the cap off as you do when I owned cars with capped radiators and tanks. I could hear air bubbling when I was refilling it, so I assumed it was bleeding itself. I know nothing about how the "Non-Capped" radiator system works refilling it. I don't remember ever doing it before when changing it and it worked fine. Any thoughts will be helpful if I'm reading that incorrectly.[/QUOTE]
With sophistication in EFI engines, not using a reader allows all sorts of speculation. Why a reader isn't used for more accurate coolant temperature measurement is questionable. Once an engine reaches operating temps via its t-stat, it doesn't matter what the outside temps are. T-stats work in a fluid environment, detecting hotter or colder coolant and varies coolant flow to regulate temps at rated specs. If the temperature needle moves up and down, its usually not because of outside temps but either the t-stat or seals related to securing the t-stat in its housing. While the radiator may have 10F degree cold air flowing thru it to super cool coolant, the t-stat is only monitoring engine coolant temps, effectively ensuring the cylinder walls aren't melting by allowing coolant flow when rated temps forces it to open to allow coolant flow to regulate engine coolant temps, not radiator temps. Whether old school radiators with metal radiator caps or present cooling systems using a plastic pressure/vacuum cap on a surge tank, both cooling systems perform the same function, to maintain cooling systems to remove excessive heat from engines.

The present cooling systems in GM have built in self bleeding whether the coolant pressure cap is screwed on or left off after a drain, flush and refill procedure. On level ground, refilling an empty cooling system always leaves air in its system, seen as bubbling during refilling procedures. On initial startup, the water pump runs to move coolant. Since the t-stat is closed, coolant flows thru an alternate path thru the heater core. The heater core doesn't have a shutoff valve. Any air trapped in a system is forced out of the engine to the heater core. The heater core empties into the coolant container. Trapped air is forced out immediately into the coolant container, seen as lowering coolant level. As the engine heats up, the t-stat opens to allow coolant from the radiator to flow thru. Cooling down, the t-stat closes, always regulating engine block temperatures.

Topping off should occur within the first few minutes right after refilling a cooling system, preferably with the coolant cap off. Once bubbling stops, coolant level ceases to lower, the cap is put on. The car should be either idled in the driveway to allow pressure and operating temps to come up or driven around the block then coolant level checked again. In normal conditions, all air was purged either from initial fill up/start up with any remaining air purged after driving as operating temps are reached. The coolant tank is the only way to assess coolant level. It's also pressurized since it is integrated into the cooling system. The air in the container allows for expansion and contraction for better system operation since it provides a way for coolant to expand under pressure without losing it compared to older radiator systems with caps that allowed the overflow to the ground or into a container. Metal and plastic pressure caps have a vacuum valve to allow coolant to return in older cooling systems with present coolant containers allow air back into the small space. Since radiators are large and aerodynamics called for streamlining the front end, removing the radiator cap lowers the radiator height. Adding a coolant container and plastic pressure/vacuum cap fulfills and improves the cooling system.

My guess is the old seal softened and allows hot coolant flow. T-stats tend to remain reliable for the most part. T-stats have only one enemy - oil contamination. Service manuals always mentions if a cooling system is contaminated with oil, the t-stat should be replaced immediately. Older rubber seals soften from petroleum. Some synthetic seals also suffer from oil contamination so its wise to simply replace them when called for. The t-stat element uses a wax pellet and my guess is wax isn't compatible with motor oil or fuel.

Below are snapshots of t-stats from the S-series forums. Engines overheating from the infamous original coolant sensor caused these seals to melt.

Dsaturn 01-22-2020 07:25 PM

Re: High engine fan speed in cold weather...a brief story...
 
[QUOTE=lrbraner;2340710]Have you had problems with the fail safe thermostats ?[/QUOTE]Never used one in a Saturn but have had them fail in a Subaru and Chevy. One in Subaru cost me a head gasket because I was miles from anything in AZ and had to drive it home over heating. Will never use one again.


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