Temperature problem

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Baldan Dugly

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I have a 2001 Sunfire with the 2.2L. I recently replaced the head gasket and the thermostat. Now at highway speeds it runs cool at around 150 degrees. I thought the thermostat was bad so I bought a new one and backflushed the heater core because I read that a clogged heater core can cause this. It used to run at 195 degrees constantly. I really don't mind except on cold mornings my heater is not as hot as it used to be. Any ideas?
 
You may have air in the cooling system but typcially the engine runs hot and the heater blows hot and cold. You are sure the thermostat was stamped 195?
 
melsg5 said:
You may have air in the cooling system but typcially the engine runs hot and the heater blows hot and cold. You are sure the thermostat was stamped 195?
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Yes, It is stamped 195. In city traffic, it runs at 195. 150 at highway speed. How do you remove air?
 
when it reads 150 are the engine fans running, if so you have a stuck relay or bad temperature sensor? I dont think you have air because you are not overheating and the 2.2 shouldnt be a problem with air bleeding out of the system on it's own.
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melsg5 said:
when it reads 150 are the engine fans running, if so you have a stuck relay or bad temperature sensor? I dont think you have air because you are not overheating and the 2.2 shouldnt be a problem with air bleeding out of the system on it's own.
Click to expand...

All is functioning normal. I shouldn't complain, but I was worried that the low temp might be indicative of component failure. I wouldn't want my new head gasket wasted for nothing.
 
you should not be running 150 on the highway there is something wrong, are the fans running at 150?
 
then there is no way you are getting a true reading on the highway of 150 with a 195 thermostat. The sensor or the gauge is having an issue.The fans are supposed to come on way past 195, closer to 215 - 220, wonder if the sensor is the culprit.
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Now you see my problem. The temp only drops to 150 when the engine is revving at highway speeds (3000 rpm). Driving around town at low rpm, the cooling system seems to function perfectly.
 
hey i have a 2001 pontiac sunfire i had the same problem i ended up replacing the head gasket, water pump, thermostat, radiator...it ended up being i needed a new thermostat housing...and also there is a little bleeder on one of the line that u can bleed the air out of the lines also...but i hope i was able to help
 
Hello everyone. It's getting cold again. Please reread the thread and update any experiences. Car ran fine all summer. On really cold days the car acts like it missing the thermostat. Is it possible that I could have bought two bad thermostats? Maybe I should buy a GM thermostat instead of autozone. Around town driving is normal. Heater is hot, fans cycle, and car maintains a temp near 200 degrees. At high revs like highway driving, the temp drops to above 100 degrees and the heater is warm instead of hot. This is really perplexing. A post above mentioned a bad thermostat housing. I inspected it thoroughly last time and could not find any damage.
 
take your thermostat and hange it in the middle of a pot of water. Slowly bring the pot to boiling. The thermostat should start to open, 195 degrees, only a little before the boiling starts, 212 degrees
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I decided to try everything at once. I replaced the autozone thermostat with a new one from napa. My napa store only stocked an oem type 180 degree thermostat. Then I bought a flush kit that you splice into a heater hose. Since my bleeder was ruined, I used the flush connector for that purpose. I cut the bad bleeder off of the steel heater line and spliced the flush where the bleeder was. When done the heater worked perfectly. Pics are attached.


Original line



New heater hose installed over the old pipe.



Finished project.

 
Glad you got it fixed, guess it was a bad thermostat again!
 
Maybe. Also could have had air in it. I flushed the system with a water hose for 10-15 minutes after installing the flush adapter. Based on research and comments from this and other sites, I tried all the remedies at the same time. So a clean system, without air, and a new thermostat seems to have conquered the issue. Thanks to all for your help and input.
 
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