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I have a 2005 Chevy Cobalt that has started overheating, so it would seem. I noticed that the coolant led jumps from normal temperatures around 189 then goes to 302. I often get the engine light coming on. I've had the codes read at the dealership and they say that it's just a random misfire. I got up this morning and decided to inspect the engine before starting it and noticed that a 2 inch coolant hose from the coolant tank was collasped. Could this be a thermostat problem? Also the fan comes on after about 1min of starting the engine but seems to be on high. The fan also runs one for about 5 minutes or more periodically when the engine is turned off.
Optional Information: Year : 2005Make : ChevroletModel : Cobalt - BaseEngine : 2.2L Already Tried: I've tried taking the car to the dealership and they have no concrete solutions. Only speculations. Sometimes the car loses power while driving up hills or on the flat road.
Since I seriously doubt your engine would be alive after running 302 degrees I suspect you either have a bad coolant temp sensor or a wiring defect causing a short. The collapsed hose is fairly normal although I would replace the cooling system fill cap because it should not hold vacuum like that. Virtually all your other symptoms coould be related to the improper coolant readings though. The one code I'm surprised they didn't see was an overtemp code though, maybe the computer didn't see it for long enough.
One other important fact that I forgot to mention is that the coolant display sometimes reads - - -F . I will replace the cooling system filler cap and most likely the coolant temp sensor. Where is that sensor located? The dealer used a temp gun when I had the - - -F reading and found that the vehicle wasn't overheating. In fact the temperature was at 145 F. During this time I experienced loss of power and kept hearing a loud vibration from the engine. These issues have baffled the technicians for about 2 months now. I had to replace my battery 2 weeks ago. It just died and would not hold any charge for all time.
The coolant temp sensor should be near the thermostat, follow the upper radiator hose down. The ---F problem could get a little difficult. Did they have a scanner on it when it did this? Because if the scanner reads correctly and the cluster reads nothing it could be a cluster issue.
They didn't use the scanner that connects to the computer. The used a hand-held laser temp gun.
See that would be important to see. If you knew the computer was reading correctly and the dash said --- it would indicate a loss of communication to the cluster.
Experience: 20 years auto repair experience, ASE Master Tech, Mechanical Failure consultant, Expert Witness