coolant temp rising and rising.


Asked by Jul 05, 2014 at 05:34 PM about the 2008 Chevrolet Cobalt LS

Question type: Maintenance & Repair

just had the serpentine belt on my car replaced by GM. now the coolant temperature gauge is out of control. its worst when idling and just keeps rising and rising. (fan not engaging? I haven't had time to check that yet.) I've been blasting the heater to compensate but all that does is slow it down. usually it runs around 75 degrees. but now it is starting out at 80 and going up 100 pretty fast.
its the 4 door sedan model. 2.5 I believe.   
the car was totally fine before having the belt replaced. I checked it last night and the new belt is still there. car is still covered under warranty too.  
what could have happened?

5 Answers


Sounds like they misrouted the serpentine belt when they installed it. If this is the case your water pump may very well be spinning backwards from the direction it was designed to go. Note that on some vehicles the water pump is supposed to spin opposite the direction of the crankshaft. You should have a serpentine belt routing diagram sticker under the hood. Compare it to how your belt is installed. HTH. -Jim

1 out of 1 people think this is helpful.
John Carson

Have your fluid checked. They may not of cleared out any air pockets and your running very low on fluid. Did they change your water pump also? If so make sure it is the correct one. If you have a friend with the same model car, compare their belt routing with the one you have on the car. If it is under warranty, go back to them or another car dealer you trust. If you got a 2008 car, is it under the 30 day warranty or just the repairs covered. Take it back and have them fix it.

2 out of 2 people think this is helpful.

I checked and topped off the antifreeze and oil and it seemed to help a little but its still running too hot. they did not change the water pump as far as I know. but they wanted $500 to replace the belt before we told them where they could stash that. it was still a $300 job. I bought the extended warranty and its still good. belts are not covered. ha ha go figure. it seems that they will fix something that is wrong with the car but they always pretend that its something that is not under warranty. for example, they might lie and replace the alternator, but charge me $500 for a belt. this is the GM dealership. >:( I get no honesty or explanations from them so its really hard for me to diagnose anything.

1 out of 1 people think this is helpful.

I can see $150 to do just the belt ($75 for the belt and $75 for a half hour of labor to put it on) but not $300 to $500. Are we talking about the serpentine belt that drives the accessories (water pump, alternator, etc.) or the timing belt (inside the engine)? -Jim

John Carson

I have gone to the dealership for factory warranty work, but most all other if I can't do it myself or don't have the time, I found an independent repair facility that I have used for over 25 years. He covers all warranty work, does it right, will at times fix at no charge little things, and is great at explanations on what is wrong. 1/2 or less the dealership costs also. He will show his invoice for the parts replaced and I get it as his cost. Yes dealerships charge $300+ for a belt change out, but it takes less than an hour depending on what must be removed and replaced. When driving and it starts to hear above normal operating temp, pull over to a safe place and raise the hood. Can you hear or see if the fans are working? If not, there is your problem. Unplugged or lose/broken wire done by them doing the work. If the fans are running, check the hoses visibly and make sure they are not collapsing under pressure. They should then be replaced. (Not covered by warranty BTW) See if the thermostat is covered by warranty. If so have them change it out. The fans should be covered also. What I would do is ask around with friends for that little independent repair shop and see if they honor the warranty. It wouldn't hurt to talk to that shop about repairs, warranty work, and cost. Dealerships make money by charging by the hour no matter if the job takes 15 minutes or an hour. The labor cost is the same. If they go over the estimate, they bump it up again. Ask the little garage if they do the same or charge for time spent. Why was the belt changed? If you just bought the car from the dealer, it should have been checked and in good operation when you drove it off the lot. Are you sure it needed replacement? Normally they are good for at least 60,000 miles.

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