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2002 gmc envoy_sle
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Discussion Starter · #1 ·
alright, so yesterday i replaced the thermostat following the directions from the how to thread somewhere around here. I replaced it because the truck just passed the 100,000 mile mark and the gauge was consistently reading 1-2 ticks below the 210 mark. After replacing the t-stat i went for a 20-25 minute drive on the freeway trying to warm it up.....but now instead of being 1-2 ticks below 210 it is now 4-5 ticks. What happened? Does anyone have any suggestions?

I used the dex-cool anitfreeze that you can get at wallmart and i got the thermostat from this shop down the street called parts plus. I would assume its the right one...otherwise i dont think it would have fit....
 

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2003 chevy trailblazer_ls
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did you test it in boiling water before putting it in?
do you have access to a OBD scanner?
you may want to see what temp the computer is seeing.
 

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2005 chevy trailblazer_ls_ext
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:iagree: I never install a thermostat in a vehicle anymore without first testing the thermostat as Rbarrios described above - especially if it's as hard to change as the ones on our I6 engines.
 

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:iagree: I never install a thermostat in a vehicle anymore without first testing the thermostat as Rbarrios described above - especially if it's as hard to change as the ones on our I6 engines.
:iagree: :iagree: :iagree:
Always and Always check. Far too much work without checking. Also did you change the upper and lower rad. hoses????? They are cheap when you look at the t-stat + Dex Cool cost. PS: the t-stat should say 195 on it.
 

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Discussion Starter · #5 ·
No, sadly i did not test the damn thing. And no i don't have an OBD scanner, but could i take it to an autozone or something and get them to test it for free?

And yes, i'm pretty sure that it is a 190 degree thermostat. It looks like the brand it stant. The radiator hoses are fine also. Is low temperatures a sign of the thermostat simply not working?
 

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No, sadly i did not test the damn thing. And no i don't have an OBD scanner, but could i take it to an autozone or something and get them to test it for free?

And yes, i'm pretty sure that it is a 190 degree thermostat. It looks like the brand it stant. The radiator hoses are fine also. Is low temperatures a sign of the thermostat simply not working?
Either the thermostat is opening too soon and/or stuck open, or the temperature sending unit is sending a bad signal to the PCM or your gauge is wrong. Most of the time it is a bad thermostat.
 

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2004 chevy trailblazer_lt
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I just changed mine last weekend and it did a similar thing the first time I cranked it and let it heat up. After 2 or 3 cycles things seem to work properly. Running now about 1 notch below the 210 mark. Have you driven it anymore since then?

david
 

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Discussion Starter · #8 ·
Yeah, i was driving it today some and it has started to fluctuate a little. The needle now rides between 1 line below 210 to about 3 lines below. I was watching it and the temp seems to drop the most while i am braking/stopped. It comes back up a little though when i am cruzing at highway speeds.
 

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Thermostat

I had the same problem after I change my stat so emperature stay I went to the dealer and bought a new one for $56+tax and changed again this time the stat is good and the temperature stay one line on the left of 210.Returned the first one to Autozone and complain with the manager.
 

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Thermostat

I had the same problem after I change my stat. I went to the dealer and bought a new one for $56+tax and changed again this time the stat is good and the temperature stay one line on the left of 210.Returned the first one to Autozone and complain with the manager.
 

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Discussion Starter · #11 ·
I had the same problem after I change my stat. I went to the dealer and bought a new one for $56+tax and changed again this time the stat is good and the temperature stay one line on the left of 210.Returned the first one to Autozone and complain with the manager.
Yeah i still haven't changed mine out since i replaced it b/c it was such a pain in the ass the first time. After you replaced your t-stat the first time and it was doing that, did your truck ever throw any codes? Sometimes i'll look down and my temp gauge will be running like 5 ticks below 210 and then jump back up to just one tick below and do this back and forth for the whole time im driving...but the service engine soon light never comes on....
 

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2002 gmc envoy_slt
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My temp gauge kept dropping so I changed my t-stat. The old one was stuck open. After the change, it was still doing it. I changed the coolant temp sensor above the t-stat and I've been good since.
 

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Wow this sounds familiar! I read this thread before changing my thermostat and after taking about 5 hours changing mine out today (of course that also includes a lunch break, flushing the system and replacing the hoses), I now have this same problem!! I did test the thermo before and it opened up right at around 195 degrees. I have started and stopped the engine and have gone for a couple of rides after but it still reads between the 210 and the big tick below it kind of sounds like that is the problem other people are having. Also when I checked the coolant temp range with one of those cheap Prestone bulb testers, it says I only have protection to -10F. FYI, I used the Prestone universal coolant and mixed it 50/50 with water.Does anyone know if that tester reads different with the universal type of coolant? (I hope, I hope!)
 
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