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Old 11-21-2022, 08:29 PM   #1
93twincam
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Default Another poor heat thread...

2002 SL1 165k miles.

Just bought the car and during the first cold day we had (22F) I went for a drive @70mph and had zero heat. My OBD2 scanner never showed greater than 197F and it took a while to reach that temp. When I got home, I left it running and felt both rad hoses. The lower rad hose was cold, the upper hose was just warm. I reached behind the engine to feel the heater hoses and they were both cold. This made me suspect a bad thermostat, and the WP was leaking so time for some maintenance.

Today I replaced the WP and the thermostat. Let the car warm up idling in the garage watching ECT with my OBD2 scanner. Temp got up to 225F (which tells me the ECT reading is accurate) then heard the fan kick on. Both rad hoses and heater hoses were too hot to touch. Awesome! Went for a test drive @ 70mph and 40F ambient. Ran the fan speed at 3 and was barely getting warm air. Bumped fan speed down to 2 and it was warmer, but not very impressive. When I move the HVAC temp knob I can hear the blend door moving and the temp does get very cold when turning all the way to cold, but only Luke warm when turning it to hot. Again, it sounds like the blend door is moving all the way.

I guess I don't know where to go from here. Seems like the system is working correctly, but heat is weak. I think I recall reading on the forum about the SOHC cars having weak heat, and some guys would block half the radiator with cardboard in the winter. This was years ago when I read these things, and at the time thought that was odd. Is this true? Am I'm going to have to block half the radiator, or am I missing something?
...
2002 SL1 5 speed - 165,xxx - Current daily
1993 SC2 5 speed - 200k - Unfortunately sold
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Old 11-21-2022, 09:21 PM   #2
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Default Re: Another poor heat thread...

This may seem a long way off but without a history of this vehicle other than year, mileage, new water pump, t-stat, feeling both heater hoses too hot to hold and reader displaying well above 195F (t-stat rating), the heater core may be blocked, physically.........with debris covering the heater core. The only way to find out if debris collected and covered the heater core is removing the blower motor and using a go pro or cellphone, snapshots or video and reviewing them.
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Old 11-21-2022, 09:50 PM   #3
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Default Re: Another poor heat thread...

Quote:
Originally Posted by fdryer View Post
This may seem a long way off but without a history of this vehicle other than year, mileage, new water pump, t-stat, feeling both heater hoses too hot to hold and reader displaying well above 195F (t-stat rating), the heater core may be blocked, physically.........with debris covering the heater core. The only way to find out if debris collected and covered the heater core is removing the blower motor and using a go pro or cellphone, snapshots or video and reviewing them.
That's a good theory, I hadn't considered that. Seems not very likely that the heater core is blocked with debris but I'm out of ideas. I'll take a peak inside and see if I can see anything.
...
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1993 SC2 5 speed - 200k - Unfortunately sold
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Old 11-22-2022, 09:23 AM   #4
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2001 SL1
Default Re: Another poor heat thread...

First of all, 197F is a more then decent running temperature but you indicated that it was slow getting there so you did likely need a thermostat. The operating temp of all S Series is ~193F and is controlled by the thermostat which is designed to crack open at 188F and is fully open at 195F. So at a cold start you shouldn't feel any heat in the upper radiator hose for a couple minutes until the coolant temperature hits 188F. The upper hose is the inlet from the engine side and the lower is the outlet so what you observed is correct. When there is no air moving through the radiator the temperature will rise to 221F and the PCM will command the fan on. It will cycle off at 213F. So your fan seems to be working fine.

If you put in an OEM or OEM style thermostat (Stant 14279) into an aftermarket thermostat housing (like MotoRad), then it is likely that the thermostat is not fully opening. An OEM or OEM style must use an OEM housing. That doesn't sound like your problem but I thought it is worth mentioning.

With regards to cabin heat there's a couple things that could be going on. The SOHC engine doesn't create much heat to begin with so that's not working on your side. One problem might be that the external air flow through the heater core is being blocked as fdryer mentioned. The other is that you may have a partial blockage of the internal heater core. It's allowing some flow but not full flow. It could be both.

For the external, is there a screen over your HVAC air inlet? It is an oval opening under the hood at the base of the cowl on the passenger side. It is supposed to have an foam gasket with screen and if missing then it is quite possible that there is debris in your HVAC air inlet duct. This also would allow rodents and insects into the HVAC. The debris would collect on the evaporator core and heater core. A build up of fine contaminants is also feasible (pollen, dust, dirt, etc...) with the screen in tact.

For the internal the best way to test is to remove the heater core coolant lines and back flush with a hose. You'll either get discharge of sorts or note that the flow is restricted. From there you will know where to go.

It is recommended that you don't use the HVAC fan or only use it on low until the engine reaches operating temperature. The HVAC fan will pull a lot of heat away from the engine which will compound the poor heat issue. In my 10+ years of owning an SOHC I never got adequate heat for short drives. Longer drives (>30min) it was comfortable.
...
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Past Saturns
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Last edited by trottida; 11-22-2022 at 09:36 AM.
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Old 11-22-2022, 10:49 AM   #5
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Default Re: Another poor heat thread...

Thanks for then info. I couldn't locate an OEM thermostat in the area so I went with a Duralast tstat and housing, which appears to be a motorad based off the casting, so I don't think that's my issue.

I'll double check the fresh air inlets and for external blockage on the heater core. If all that checks out, I'll try a heater core flush, although based on my highly accurate calibrated hands, both heater hoses felt like they got hot simultaneously which to me implies there isn't a restriction, at least not a great one. I know that's not entirely scientific but it was good enough for me at the time.

I also see your point about the SOHC being slow to heat up. I did notice when I turned the HVAC fan the temp gauge started to slowly go down a bit. Maybe the issue here is my impatience, and maybe too high of expectation. My truck will cook you out of the cab in no time at all, I have to run it way down on low to survive.

I'll check for restrictions and go from there.
...
2002 SL1 5 speed - 165,xxx - Current daily
1993 SC2 5 speed - 200k - Unfortunately sold
2002 Silverado Z71 - 185,xxx
2007 Impala 3.5L - 365,xxx - Still running good, daily backup

Last edited by 93twincam; 11-22-2022 at 11:01 AM.
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Old 11-22-2022, 12:18 PM   #6
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Default Re: Another poor heat thread...

If you have a block heater that will help get the engine temp up faster.

Quote:
Originally Posted by 93twincam View Post
Thanks for then info. I couldn't locate an OEM thermostat in the area so I went with a Duralast tstat and housing, which appears to be a motorad based off the casting, so I don't think that's my issue.
Keep your original housing in case you need it in the future.

Quote:
Originally Posted by 93twincam View Post
I also see your point about the SOHC being slow to heat up. I did notice when I turned the HVAC fan the temp gauge started to slowly go down a bit. Maybe the issue here is my impatience, and maybe too high of expectation. My truck will cook you out of the cab in no time at all, I have to run it way down on low to survive.
Compared my other 2 vehicles the Saturn is notably slower to heat up the cabin. I have a DOHC now which provides better heat than the SOHC. Both the Suburban and Focus have Auto HVAC and it does not cycle the HVAC fan on until the engine temperature is up to operating temperature. They are both faster at getting the engine warmed up than my Saturn.
...
1999 SL2 MT (311,300 km @ 01/2023)
2012 Ford Focus SEL HB MT
2011 Suburban LT

Past Saturns
2001 SL1 MT (438,500 km 11y)
1993 SW2 AT (10y)
2001 LW200 MT (3.5y)
1992 SL2 MT (5y)

:canada:

Last edited by trottida; 11-22-2022 at 12:23 PM.
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Old 11-22-2022, 01:05 PM   #7
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2002 SL1
Default Re: Another poor heat thread...

My 93 SC2 had better heat than this SL1 does, which may be why I'm so concerned about it. I had a hard time believing the SOHC would be notably different than the DOHC, but now having owned both I can see its true.

I think the issue is my impatience. Went for another drive today, about 40 miles on the interstate, 33F ambient. I waited to turn on the heat until it reached full op temp. Then, started with fan speed 1 and recirc, the worked my way up to speed 3. Eventually the cabin heated up and I had to turn it down a bit. I think it's operating correctly, I just need to readjust my expectations and increase patience.
...
2002 SL1 5 speed - 165,xxx - Current daily
1993 SC2 5 speed - 200k - Unfortunately sold
2002 Silverado Z71 - 185,xxx
2007 Impala 3.5L - 365,xxx - Still running good, daily backup
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Old 11-24-2022, 01:04 PM   #8
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Default Re: Another poor heat thread...

I agonized over my poor heat for a couple of winters after I bought my SC1, did all the things you are doing, new thermostat, etc, then after reading that the single cams are slow to heat, I just started putting a pool noodle in the front opening for the winter.

Definitely slow to heat!
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Old 11-24-2022, 11:47 PM   #9
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Default Re: Another poor heat thread...

Quote:
Originally Posted by Ricketts View Post
I agonized over my poor heat for a couple of winters after I bought my SC1, did all the things you are doing, new thermostat, etc, then after reading that the single cams are slow to heat, I just started putting a pool noodle in the front opening for the winter.

Definitely slow to heat!
Hey, now there's a good idea. I was trying to think of a way to block half the radiator, that would be easy to install/remove and made of a material that wouldn't degrade when hit with moisture/salt from the highway. A pool noodle in the facia opening is brilliant! Do you block the entire opening, or just a portion of it? Did it make that much difference?
...
2002 SL1 5 speed - 165,xxx - Current daily
1993 SC2 5 speed - 200k - Unfortunately sold
2002 Silverado Z71 - 185,xxx
2007 Impala 3.5L - 365,xxx - Still running good, daily backup
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Old 11-30-2022, 02:23 PM   #10
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1995 SW2
Default Re: Another poor heat thread...

I've been driving a SOHC or DOHC Saturn of one flavor or another in Michigan for over 15 years and I've never had an issue with heat when the cars are working properly. I've had several thermostats stick open which lead to the car taking forever to warm up. Just because a thermostat is new doesn't mean it is good. Especially these days.

The other overlooked cause of poor heat is low coolant. Make sure the system is properly filled and burped.

I've never had to block airflow through the radiator or do anything other than drive the car to get heat. If the thermostat and coolant level are good then I would look at the heater controls and then the heater core.
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Old 12-02-2022, 08:51 PM   #11
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Default Re: Another poor heat thread...

The single cam engines just don't make a lot of heat. Beyond checking out the basics, don't overthink it. Though it's enough heat, it's not much compared to a twin cam or for that matter a LOT of other cars.

With everything perfect, they still don't create much heat until under some load. I just put the heat on when I scraped the windows, drove off with minimal defrost, and within 3-4 miles things were better.

With the larger gauge sweep on the earlier models, I could actually watch the gauge on our '95 sweep up as I made the third gear pull onto the highway. Even if I was heavy on the gas pedal, it didn't quite get the car to temp on the cold days.
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Old 12-03-2022, 10:48 AM   #12
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Default Re: Another poor heat thread...

I may give the core a flush for good measure at some point. Heat is sufficient for now though and it's a bit cold out to be using a garden hose.
...
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Old 12-03-2022, 11:16 AM   #13
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Default Re: Another poor heat thread...

I put a pool noodle in the lower grill slots…

You could also use pipe insulation…

I left the middle open…
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Old 12-03-2022, 11:19 AM   #14
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Default Re: Another poor heat thread...

Quote:
Originally Posted by mattwithcats View Post
I put a pool noodle in the lower grill slots…

You could also use pipe insulation…

I left the middle open…
I plan to do that as well.
...
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Old 12-04-2022, 10:26 PM   #15
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Default Re: Another poor heat thread...

Quote:
Originally Posted by 93twincam View Post
Hey, now there's a good idea. I was trying to think of a way to block half the radiator, that would be easy to install/remove and made of a material that wouldn't degrade when hit with moisture/salt from the highway. A pool noodle in the facia opening is brilliant! Do you block the entire opening, or just a portion of it? Did it make that much difference?
Sadly it wasn't my idea, I can't remember who on here mentioned it years ago, but it works great. I did have to add a layer of extra foam around the noodle as I still had a small gap when inserted. I trimmed it to fit the smiley portion of the opening, and it stays nicely in place, and is easily removed and reused every winter. I used one piece right across the whole opening. I live in a small town, but I could see where using it in stop and go traffic in a larger city might have a chance to run warmer than needed
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Old 12-05-2022, 09:37 AM   #16
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Default Re: Another poor heat thread...

Quote:
Originally Posted by Ricketts View Post
Sadly it wasn't my idea, I can't remember who on here mentioned it years ago, but it works great. I did have to add a layer of extra foam around the noodle as I still had a small gap when inserted. I trimmed it to fit the smiley portion of the opening, and it stays nicely in place, and is easily removed and reused every winter. I used one piece right across the whole opening. I live in a small town, but I could see where using it in stop and go traffic in a larger city might have a chance to run warmer than needed
Most of my driving with this car is highway. When I do drive in the city, the stop and go isn't too bad. But, the nice thing about the foam is it is easily "tunable." I can experiment with how much of the opening to block off under the conditions I drive in.
...
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1993 SC2 5 speed - 200k - Unfortunately sold
2002 Silverado Z71 - 185,xxx
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