2008 cobalt LT, cooling system HELP

[andygriffith]

hello, im new to the site. i mostly work on my 96 trans am so my wife's 2008 cobalt LT is soooo wierd to me, its having an overheating issue. one day it jumped up to 210 to 220 at idle. before this it was always in the 180s unless going up large hills. i checked the thermostat and it was good, the fluid was a little low and old so i flushed it and filled it up about three times. this helped but didnt fix the issue, i then noticed that the fans were not coming on but i had to be at work so i tried driving it. as long as i kept it moving the air flow from driving kept it cool enough, 190s. after doing this for a few days it stopped being as effective and sometimes worked very well sometimes i heard and saw the fan come on when i got to about 210 but not all the time, when driving sometimes it wouldnt cool so i hit the gas till i got about 4000rpm and let off and it would start to cool. but it started to get cold here and it was still very hot even when it was just started 5 minutes ago in 32 degree weather. so i replaced the temperature sensor. as far as i can tell there is only one on the engine. then my temperature readings were accurate. but after the car heated up to running temp 50% of the time it would start getting into the low 200s. so i tested the 2 fan fuses and they were good, i tested the one and only fan relay inconclusively. i could only get the car up to 190 this time but at no time did the really engage, i replaced it to be sure(in hindsight i could have switched the headlight one to check it) and i still could only get to 190 (i got 210 yesterday) and no click, so this was inconclusive. i cant disconnect the fan without removing the housing because the lead connects very close to it. any thoughts ideas, please help.

 

[YelloEye]

Fans are set to turn on around 205-220 if I recall correctly. You can force them on by turning on the A/C and HVAC to any setting but off.

 

[andygriffith]

so the a/c must be on with the air, but does the air temperature matter hot/cold.

 

[YelloEye]

Nope, the fans come on any time the compressor is engaged regardless of temperature setting. Which is when either the a/c button is pressed or if the selector is anywhere between floor and windshield, you actually have to go one click left of floor to turn off the compressor.

 

[andygriffith]

thank you, i let it get to 183 turned on the air, full blast hot with a/c, didnt work right away, so i switched to cold, and it started working, so i switched back to hot, and it still worked. so i guess it just took the pcm a minute to think. short of getting it in the 200s to check normal operation i think im good to go, do you know where i can find the rest of the schematics or the full manufacture's manual, again thank you.

 

[YelloEye]

You can order the service manuals from Crate Engine Depot, great investment I think.