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Old 10-14-2008, 07:55 PM   #1
LS1_Fonzie
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Default Temp gauge reads low but still getting good mpg...question

This is for a 1992 SL1 5 speed car. So I've noticed my temperature gauge reads really low, and after searching and reading a few threads on low temps I noticed it could be a sign of a bad ECTS or thermostat. But what I noticed in those threads is that they were accompanied by poor MPG or other problems. So far I haven't noticed any problems with the car. Still getting 41mpg, temperature gauge moves up and down accordingly when I'm in stop and go traffic, I usually only see the low temperatures during highway driving. Any suggestions? Here is a pic for reference.

...
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Old 10-14-2008, 08:00 PM   #2
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Default Re: Temp gauge reads low but still getting good mpg...question

thermostat probably? or the gauge itself maybe

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Old 10-14-2008, 08:05 PM   #3
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Default Re: Temp gauge reads low but still getting good mpg...question

I would replace the ECTS with the genuine Saturn part, in addition to the thermostat (Saturn part again) if that hasn't been done recently.

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Old 10-14-2008, 08:06 PM   #4
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Default Re: Temp gauge reads low but still getting good mpg...question

u have 2 different sensors. One for the pcm and other for the gauge. The gauge has one wire going into it. Follow the radiator hose from the airbox to the head and its right behind the clamp. Do this change on a cold car since the coolant is HOT!! i burned myself when i wasnt paying attention.......

...
now with problems and getting a newer car but not a saturn :(
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Old 10-14-2008, 08:32 PM   #5
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Happy Re: Temp gauge reads low but still getting good mpg...question

I will vote T-stat.....

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Old 10-14-2008, 08:50 PM   #6
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Thumbs Up Re: Temp gauge reads low but still getting good mpg...question

That definitely looks low. I just bought a 1995 SC1 with a slightly higher reading -- it would ride along at the 1/4 mark all the time.

Replaced the thermostat, and now it rides along at the 1/2 mark. Right where it should be.

Could be the sensor or the gauge, but it is most likely the thermostat. Replacing the thermostat should allow the engine to operate at the right temperature. This should have a positive effect on your MPG.

You'll have the drain the coolant to replace the thermostat -- you ought to consider replacing it, too.

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Old 10-14-2008, 11:07 PM   #7
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Default Re: Temp gauge reads low but still getting good mpg...question

Quote:
Originally Posted by aa4lr View Post
That definitely looks low. I just bought a 1995 SC1 with a slightly higher reading -- it would ride along at the 1/4 mark all the time.

Replaced the thermostat, and now it rides along at the 1/2 mark. Right where it should be.

Could be the sensor or the gauge, but it is most likely the thermostat. Replacing the thermostat should allow the engine to operate at the right temperature. This should have a positive effect on your MPG.

You'll have the drain the coolant to replace the thermostat -- you ought to consider replacing it, too.
I'll look into getting a new thermostat. If I can improve on the 41 MPG I'm getting now then I'm all for it. I bought a new thermostat for my Camaro from Kragen and it's been working great since I got it, should I go with another Kragen T-Stat for the Saturn or is there a specific reason for going with one from the dealership? (And GM needing my money during this economic meltdown doesn't count as a valid reason )

...
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Old 10-15-2008, 04:49 AM   #8
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Default Re: Temp gauge reads low but still getting good mpg...question

What you describe sounds like a stuck-open t-stat. When you replace it, be sure to get the right temp range. Stant 195 degree works, as does the OEM. Can't speak to Kragen.

Because on on pre-'96 cars the ECTS does not drive the temp gauge reading, it is unlikely that a bad ECTS will show up in gauge readings, but it is worth checking it and changing it if not the new type, also check the connector for corrosion.

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Old 10-15-2008, 07:39 AM   #9
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Wrench Re: Temp gauge reads low but still getting good mpg...question

Quote:
Originally Posted by LS1_Fonzie View Post
I bought a new thermostat for my Camaro from Kragen and it's been working great since I got it, should I go with another Kragen T-Stat for the Saturn or is there a specific reason for going with one from the dealership? (And GM needing my money during this economic meltdown doesn't count as a valid reason )
I bought a Stant thermostat from Advance Auto Parts. This is the complete kit with the thermostat, O-ring and the cardboard insertion / removal tool. The tool looks goofy, but without it, getting the thermostat on and off is a bit tricky.

Good luck!

...
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Old 10-15-2008, 10:18 AM   #10
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Default Re: Temp gauge reads low but still getting good mpg...question

Stant makes a quality product. That is what most of the aftermarket is selling.

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Old 10-15-2008, 10:35 AM   #11
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Default Re: Temp gauge reads low but still getting good mpg...question

Thanks for the responses guys. I checked online and it looks like both Kragen and Advanced Auto Parts online orders go through partsamerica.com. I saw 2 Stant thermostats available, one for $16.99 and the other for $31.99. Besides the 1 year limited warranty for the $31.99, is there a difference between the two? Here is the link listing both
http://www.partsamerica.com/ProductL...pe=133&PTSet=A

...
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http://www.cardomain.com/ride/2142863

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Old 10-15-2008, 11:03 AM   #12
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Default Re: Temp gauge reads low but still getting good mpg...question

The partsamerica link will not work for most. Its zip code specific so it can serve up the local price. The only way to sort it out is to call your local store and ask them. The price difference is only the warranty. I get the base for 16.95 and the 1 year warranty for 23.05.

Last edited by OldNuc; 10-15-2008 at 11:12 AM..

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Old 10-15-2008, 11:19 AM   #13
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Default Re: Temp gauge reads low but still getting good mpg...question

Ok, I'll go talk to them in store. Thanks again for the responses.

...
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http://www.cardomain.com/ride/2142863

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Old 10-15-2008, 11:30 AM   #14
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Default Re: Temp gauge reads low but still getting good mpg...question

But Rockauto shows the two as essentially the same price. The difference may really be the packaging (box vs. blister pack)

Last edited by DonP; 10-15-2008 at 11:35 AM..

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Old 10-15-2008, 11:31 AM   #15
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Default Re: Temp gauge reads low but still getting good mpg...question

As near as I can tell its the 1 year warranty that is the difference.

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Old 08-31-2009, 02:40 PM   #16
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Roll Eyes Re: Temp gauge reads low but still getting good mpg...question

I have read this thread and have a question about the proper temp range for a 1995 Saturn SL2. I bought it used about a year and a half ago. The temperature gauge has always read at the 1/4 mark in normal city and highway driving. I like that. When I am stuck in traffic for a long time it will creep up to the 1/2 mark or a little above. Last year in summer I got stuck in stop and go traffic trying to go through Atlanta and the gauge went up to the 3/4 mark and was approaching the red even when I turned off the a/c. While still in stop and go traffic it suddenly went back down to below the 1/2 mark - maybe it was a cooling fan kicking in, I don't know.

Anyway, I like it at the 1/4 mark even though my mechanic and experts on the forum say it should normally be at the half-way mark. 1/4 is my personal comfort zone.

Question 1. - If it normally is at the half-way mark and I get stuck in traffic can I expect it to creep up to the 3/4 mark or higher rather quickly. Would that be normal? Aren't some fan(s) suppose to kick in and keep it at normal temperature (1/2 at least)?

Questions - 2. - Due to my failing the NOX part of emissions test badly last week, and after replacing the EGR value and cleaning the ports and it still failed, my mechanic in troubleshooting replaced the thermostat with one that makes it run at the 1/2 way mark (I told him I liked it at the 1/4 mark even though he said that was not normal and it should be running at the 1/2 way mark) and also replaced, I believe it was the oxygen sensor right in front of the engine (he showed me it sticking out.) My NOX test then passed just fine.

My questions -

1. Was it the thermostat change or the sensor replacement or both that contributed to dropping the NOX down to acceptable levels?

2. How much change in MPG can I expect from a higher running temperature engine?

Note: My car passed the NOX test when he sold me the car and gave me the emissions test he had to do and also the first year I had it with the lower-temperature thermostat. I have to belive it was more the sensor replacement that did the trick. (The old T-state he gave me says Made in germany and 1/5 on it. That's it.

I prefer the lower temp thermostat unless someone says I am ruining the engine or I could get 5 or 10 MPG more with a hotter engine. (The lower T-stat must have been in the acceptable range to begin with!)

Can someone give me pros and cons and some insight into this, please? Thanks.

Frank
"Personal Preference"

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Old 08-31-2009, 03:06 PM   #17
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Default Re: Temp gauge reads low but still getting good mpg...question

Quote:
Originally Posted by FRHill View Post
I have read this thread and have a question about the proper temp range for a 1995 Saturn SL2. I bought it used about a year and a half ago. The temperature gauge has always read at the 1/4 mark in normal city and highway driving. I like that. When I am stuck in traffic for a long time it will creep up to the 1/2 mark or a little above. Last year in summer I got stuck in stop and go traffic trying to go through Atlanta and the gauge went up to the 3/4 mark and was approaching the red even when I turned off the a/c. While still in stop and go traffic it suddenly went back down to below the 1/2 mark - maybe it was a cooling fan kicking in, I don't know.

The fan comes on at 3/4 if the gauge sensor is within specs and the ECTS is within specs.

Anyway, I like it at the 1/4 mark even though my mechanic and experts on the forum say it should normally be at the half-way mark. 1/4 is my personal comfort zone.

You are running the engine in the "make internal sludge" zone.

Question 1. - If it normally is at the half-way mark and I get stuck in traffic can I expect it to creep up to the 3/4 mark or higher rather quickly. Would that be normal? Aren't some fan(s) suppose to kick in and keep it at normal temperature (1/2 at least)?

Yes, and that is the normal, proper behavior. The fan will come on at 3/4 or a hair above. That is the way it is designed to work. The fan comes on a 222F and switches off at about 205F and the temp continues to drop to 190F or so.

Questions - 2. - Due to my failing the NOX part of emissions test badly last week, and after replacing the EGR value and cleaning the ports and it still failed, my mechanic in troubleshooting replaced the thermostat with one that makes it run at the 1/2 way mark (I told him I liked it at the 1/4 mark even though he said that was not normal and it should be running at the 1/2 way mark) and also replaced, I believe it was the oxygen sensor right in front of the engine (he showed me it sticking out.) My NOX test then passed just fine.

My questions -

1. Was it the thermostat change or the sensor replacement or both that contributed to dropping the NOX down to acceptable levels?

Both

2. How much change in MPG can I expect from a higher running temperature engine?

Its not so much the operating temperature as the warm up temperature. The mixture is rich until the engine is at normal operating temp, a bit below 1/2 but not 1/4. The mileage change will depend on your driving style and driving conditions.

Note: My car passed the NOX test when he sold me the car and gave me the emissions test he had to do and also the first year I had it with the lower-temperature thermostat. I have to belive it was more the sensor replacement that did the trick. (The old T-state he gave me says Made in germany and 1/5 on it. That's it.

There is an 87C on there somewhere also. The low operating temperature and the excessive rich mixture killed the O2 sensor. So this is a chicken - egg question.

I prefer the lower temp thermostat unless someone says I am ruining the engine or I could get 5 or 10 MPG more with a hotter engine. (The lower T-stat must have been in the acceptable range to begin with!)

The "lower" temp Thermostat was stuck open. BROKE. A new O2 sensor wilprobably pass cold. It will be the hydrocarbons that will be very high.

Can someone give me pros and cons and some insight into this, please? Thanks.

Frank
"Personal Preference"
Run the car at 1/2 and let it sit and idle in the drive with the hood open and note the gauge point when the fan comes on. Then you will know when its time to get worried. Also have your coolant checked and insure that it is at least a 50% antifreeze solution. The car cooling system will not operate properly on a lower concentration and you will significantly increase the probability of eventually cracking the radiator tank right under the inlet hose..

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Old 08-31-2009, 03:48 PM   #18
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Default Re: Temp gauge reads low but still getting good mpg...question

OldNuc said it all.

See http://www.saturnfans.com/photos/sho...5/ppuser/26410 for what to expect on the temp gauge on a happy '95 SL2.

Keep in mind that the temp gauge is just a gauge with arbitrary marks (i.e., no numbers corresponding to the coolant temperature), except for the red zone, which means overheating. Saturn changed the gauge response curve in later years because many folks did not like to see it move near 3/4. The gauge response changed, not the actual coolant temps.

T-stat markings and ratings tend to vary a bit - some show start to open temp, some show full-open temp, and some may reflect the net temperature of the cooling system in a specific applications.

Also, sonsider the S-car where the temp gauge sender & ECTS read coolant leaving the engine, while the t-stat is normally bathed by coolant leaving the radiator and thus cooler than what the ECTS & temp sender see).

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Old 08-31-2009, 09:39 PM   #19
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Default Re: Temp gauge reads low but still getting good mpg...question

Quote:
Originally Posted by FRHill View Post
I have read this thread and have a question about the proper temp range for a 1995 Saturn SL2. I bought it used about a year and a half ago. The temperature gauge has always read at the 1/4 mark in normal city and highway driving. I like that. When I am stuck in traffic for a long time it will creep up to the 1/2 mark or a little above. Last year in summer I got stuck in stop and go traffic trying to go through Atlanta and the gauge went up to the 3/4 mark and was approaching the red even when I turned off the a/c. While still in stop and go traffic it suddenly went back down to below the 1/2 mark - maybe it was a cooling fan kicking in, I don't know.

Anyway, I like it at the 1/4 mark even though my mechanic and experts on the forum say it should normally be at the half-way mark. 1/4 is my personal comfort zone.

Question 1. - If it normally is at the half-way mark and I get stuck in traffic can I expect it to creep up to the 3/4 mark or higher rather quickly. Would that be normal? Aren't some fan(s) suppose to kick in and keep it at normal temperature (1/2 at least)?

Questions - 2. - Due to my failing the NOX part of emissions test badly last week, and after replacing the EGR value and cleaning the ports and it still failed, my mechanic in troubleshooting replaced the thermostat with one that makes it run at the 1/2 way mark (I told him I liked it at the 1/4 mark even though he said that was not normal and it should be running at the 1/2 way mark) and also replaced, I believe it was the oxygen sensor right in front of the engine (he showed me it sticking out.) My NOX test then passed just fine.

My questions -

1. Was it the thermostat change or the sensor replacement or both that contributed to dropping the NOX down to acceptable levels?

2. How much change in MPG can I expect from a higher running temperature engine?

Note: My car passed the NOX test when he sold me the car and gave me the emissions test he had to do and also the first year I had it with the lower-temperature thermostat. I have to belive it was more the sensor replacement that did the trick. (The old T-state he gave me says Made in germany and 1/5 on it. That's it.

I prefer the lower temp thermostat unless someone says I am ruining the engine or I could get 5 or 10 MPG more with a hotter engine. (The lower T-stat must have been in the acceptable range to begin with!)

Can someone give me pros and cons and some insight into this, please? Thanks.

Frank
"Personal Preference"
Your temp rising in slow traffic until the fan comes on is normal operation in these cars. As for the temp, it seems that quite a few of the '95 and earlier cars ran cooler. I'd bet money if you look real close you will find on that old original thermostat it says "85C" and "Germany" on it, as that was what shipped in our '95 SL1 and most of the cars people checked here on the forum that had OEM thermostats in that year. There is a photo of the one out of our car in my photos. Our car ran above 1/4 when shipped, but not by much. At the most probably 3/8 on the gauge.

The lower temp probably did contribute to higher emissions levels, but the sensor could have played a part as well. But if the car passed earlier with the cooler thermostat it's unlikely that was the entire cause.

Once our original failed I replaced it with an 87C unit from NAPA. What I've gained is..... well nothing other than a higher reading gauge. I had a very slight MPG decrease, and the very slight "tick" of the knock sensor keeping the timing under control increased from "very rare" to "on occasion" during hot summer months with the AC on.

Since the higher operating temps seems to be a trend on '96 and later cars, my guess it that it decreased the emissions levels and was done to deal with the new OBD-II specs and the ever tightening government emissions standards.

If I have to replace it again, I'd grab the cooler thermostat if available, but it wouldn't kill me to put another 87C unit in either.

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Old 09-01-2009, 08:06 PM   #20
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Default Re: Temp gauge reads low but still getting good mpg...question

Regarding my statement from my original posting --(The old T-stat he gave me says Made in Germany and 1/5 on it. That's it. ----

OldNuc: There is an 87C on there somewhere also. The low operating temperature and the excessive rich mixture killed the O2 sensor. So this is a chicken - egg question.

Reply: I took a closer look at the old T-Stat with a magnifiying glass and found on the brass-looking cylinder surrounded by a coil the words "85 (with a small degree symbol) and capital letters "SL" underneath that.

Does that mean 85 degrees centigrade? What degrees would the new T-stat have that causes the temp gauge to stay at the 1/2 mark in normal driving?

I talked to some auto parts stores and looked online and haven't found any options as far as being able to choose different temerature 1995 SL2 Saturn T-Stats. It just says standard replacement for OE T-Stat.

So did my "original" 85 SL T-Stat just stick open or something that it would normally read at the 1/4 mark or is 85 SL really a lower than normal temperature T-Stat?

Thanks

Frank

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