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Discussion Starter · #1 ·
First I want to say I love my car. For the amount of miles it has 230000 it is a very solid car. I have been driving the car since about 180000 I bought it from an old roommate who wanted to sell it and he was the first and only owner until me. So I have a 2009 cobalt 5 speed manual transmission and the lowest dollar version so I don't have electric windows or locks no cruise nothing fancy. Last summer after I bought it it just turned 200000 and I took it on a trip 10000 miles worth of trip. When I started driving it the check engine light was on for an oxygen sensor. Well after I bought it I had 4 sensors replaced 2 o2 sensors, MAFS and i think it was throttle position sensor. The car wasn't running bad I just did it to get the light off plus I had to run it through emissions eventually. I haven't had any issue with the car accept a dead battery once.

Ok I recently took the car back home my father passed away. 2400 miles round trip, not even a hiccup. I would say a week after I get back I had the display showing tac and outside temperature. Oddly enough it was telling me that is was 140 outside...I live in arizona but its not that hot. I switched over to coolant and it was up 210 degrees which up to that point I have never seen in my car. Keep in mind last summer I spent alot of time in Laughlin nevada and I would leave my car running for hours at a time because I had my cat with me and she was left in the car sometimes so. Anyway so I seen 210 and the hotest I have seen was 187.

So I was cruising through town at that point and was about to get on the freeway so I figured it would cool down once I sped up and didn't have to keep stopping at lights. After I hit the freeway I had my ac on as well it was hot and I know that the fan kicks on high when the compressor is running for the ac. I don't have two fans that is something the automatics have i guess. But as I was driving down the freeway I noticed the temperature was slowly climbing. Once it got up to 196 or so I turned off my ac and after about a mile or so temp starts dropping and goes back down to 187 even 185.

So here is what I have done since then. I have changed the thermostat, changed the serpentine belts because i was told there was a chance that the belt might be slipping and because it needed to be changed. Now I almost did the water pump but my system is not loosing any water there is no water coming from the weeping hold on the water pump or it is not loosing water anywhere. I have observed my fan, I got the car to running temperature kicked the ac on and the fan does spin up faster. I have watched it pretty consistently during the time it starts the temperature raising past my normal, it doesn't stop or slow down. When I changed the thermostat the water radiator mixed coolant did not have anything in it no foreign entities noticeable with the human eye.

So I dont know where to go with it next. There is also nothing blocking the outside of the radiator. So I would appreciate a direction if anyone has one.
 

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196 and 210 or not high temperatures for this vehicle I live in Chicago have an 09 with the automatic my temperature usually is around 210 if I’m stuck in traffic in the summertime it may get up to 215 I think at about 220 the secondary fan kicks in you might try using the garden hose on the radiatorTo clean off Dustin debris I know you said it was not clogged. If you’re not losing any fluid I wouldn’t be concerned about it make sure your reservoir is at the correct level


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Discussion Starter · #3 ·
my car dont have a second fan i have a manual. I know that is not a high temperature it just never ran at that temp until a week ago. and i did do the garden hose thing. Maybe I should flush the radiator even though it looked clean when i put in the new thrermostat
 

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Soon after buying my ‘06 Cobalt I flushed the coolant and changed it with yellow/green Prestone. Probably didn’t need to but I’ve found lots of GM cars over the years with nasty looking Dexcool. Anyways, I also changed the thermostat with a premium part. It did have failing rubber seals that could have potentially come lose and clogged something up if I’d have left it in there.

Several months later I started to notice the temp reaching higher than normal temperatures. The worst it was it got up to about 227*. I found that the fan would run at low speed, but when it was supposed to run at high speed it would sometimes stop. I could bump the fan blade and it would start up. I believe the fan has two windings and the high speed winding was bad. After replacing the fan I’ve had no more problems. This would be the second replacement fan the car has had. I put an AC Delco fan assembly in which uses a Bosch motor. The one I replaced was a cheap made in Taiwan part.

It’s possible you’re experiencing the same issue. Maybe not though. I’ve had a bad radiator do similar things on another vehicle. It would overheat on the highway. It was clogged in that case. My Cobalt’s radiator has been previously replaced though so not much chance of it having a issues being clogged. Again I have seen Dexcool clog cooling systems. Not really sure if it’s just because lack of maintenance, using tap water, or other factors. It usually works well if the system is drained on a regular maintenance interval.
 
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