# chevy cobalt over heat



## troy deppen (Dec 27, 2010)

my boys chevy cobalt is over heating.I thought it was a themostat. iI changed it and it still over heats. The heater is not working. The cooling system was bled and full of coolant. when over heating I took the coolant resivor cap off and it erupted cold coolant. its a 2006 chevy cobalt.


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## troy deppen (Dec 27, 2010)

*help*

I really thought I would receive a reply. No thoughts from anyone


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## SABL (Jul 4, 2008)

Any circulation of the coolant?? Have you ever used well-water in the cooling system?? 

With the car being 9 years old I would check the water pump. I have seen impellers completely gone where only the backing plate was still there.


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## troy deppen (Dec 27, 2010)

I don't think it's circulating. I also feel it's building alot of pressure, but the water is cold and the engine is hot. I've seen head gaskets let compression into cooling system and will cause about the same effect. I believe the water pump could very well be bad like you say. We have only had the car for a few months and it has a rebuilt tittle. They may have used sealers witch may have plugged the radiator. I pressure tested the cooling system and water came out down where the evaporator normally drips so I know the heater core is leaking some. I had a hell of a time getting it up to five pounds. I need to get some help while I do the test so I can focus more on where the pressure is going. basically I need to do the pressure test over. There are no visible leaks but I can smell a faint smell of coolant in the car. I'm trying to go about this without alot of need less work.


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## SABL (Jul 4, 2008)

If it's a head gasket you should see churning/boiling in the radiator or coolant reservoir. Pressure will build up from overheating if the water/coolant is not moving through the system as it should.

*My son just got his truck back together after a head gasket cut loose. He wasn't so lucky with his Cherokee and it cost him a new engine after neglecting a radiator leak. His sister-in-law is the one who lost a Taurus engine when the pump impellers disintegrated/corroded to nothing. That was a first for me....I should have taken pictures. The pump was replaced but the damage had been done......I still have the new pump, which I removed before the car was scrapped.


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## troy deppen (Dec 27, 2010)

The car has rebuilt title and was hit in the front. They never replaced the radiator. I'm wondering if there may have been damage to it and somebody ran sealers and such through it. There is damage to the fan and the pick a part in town has a radiator I can pick up reasonable. I did put copper seal in it trying to get the heater core to stop leaking. I guess I'm going to get the radiator, flush all the coolant and maybe do the thermostat again. I'll let you guys know what happens.


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## SABL (Jul 4, 2008)

If they ran some type of sealers I would think the heater core wouldn't be leaking. Put the thermostat in a small pan of water and bring to a boil on the stove to see if the thermostat opens. 

Pull the hoses to the radiator and connect a garden hose to see if water flows through. 

Good luck.....let us know how things go.


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## troy deppen (Dec 27, 2010)

I put the other radiator in and a new thermostat. I did not check the flow with a garden hose. anyway it's still not circulating and over heating. Maybe the water pump is gone. really don't want to do it. Probably should it's due for a timing belt. I'm worried I go through it then still have the same issue.


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## SABL (Jul 4, 2008)

That thing looks like a pain to work on.....as is most cars today....:sigh:

I've only seen one water pump lose all impellers but I don't wrench many vehicles any more. It's worth looking into, though.


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## troy deppen (Dec 27, 2010)

I guess its chain driven. was told there's a special tool to get the pump out with out having to set timing back up. I'd like to run water through to see if the pump is pumping and check for flow but my block would be full of straight water and it's freaky freezen where I'm at. If there is air pockets in the cooling system it will cause the same problems I'm having. There is a special bleed out procedure. You supposed to add coolant to the cold fill line and then wait for five minutes topping back off to cold fill line as needed. Then run car with out cap till the upper radiator hose is hot keeping coolant at cold fill line. once upper hose is hot replace cap and you should be good to go. When I went through this as the upper radiator hose warm/hot the coolant started over flowing out of the resivor. What do you think about that? Do you know anyone who may have any ideas. I was told I probably have air in the system. I have a line above my water pump inlet that runs back to the top of the resivor. I have taken it off and added coolant until coolant came out above water pump. So I think it's bled out.


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## SABL (Jul 4, 2008)

Which engine does the car have?? I'm not familiar with Cobalts or any of the newer engines......I'm old school Small Block Chevy fan.


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## troy deppen (Dec 27, 2010)

It's a 2006 2.2.


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## SABL (Jul 4, 2008)

From what research I've done you should check the chain drive for the pump......they can break. 

This is the 2.4L but the 2.2L may be similar.


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## wolfen1086 (Oct 4, 2007)

Leave it to Chevrolet to use a bicycle chain on a car
Defiantly follow the instructions in that video, I haven't had the displeasure of doing one yet but we did scrap a cobalt( 07) and my youngest broke the motor down and took the broken chain for parts for his bike and the rest of the thing was one cent a pound


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## troy deppen (Dec 27, 2010)

I do appreciate the research. I ended up taking the water pump out. They have a special tool to hold gear and chain in place. I now own one. pump looked fine and has been replaced before. All passages are clear. thermostat works. Car is tore apart. I'll check the chain. Thanks


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## SABL (Jul 4, 2008)

I own many tools that have only been used a few times.......or maybe only once. Depending on the cost of the tool vs shop fees it is well worth buying the tool.

I hope the problem is nothing more than a broken chain which seems to be common. They've re-engineered today's cars so much that it takes special tools and techniques to make many of the repairs. In your case it sure would have been nice to unbolt the pump or replace a serpentine belt instead of tearing the front of the engine apart.....

Good luck.


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## troy deppen (Dec 27, 2010)

well boys. here's the rundown. The chain was fine. All passages seemed clear. thermostat open in boiling water. pump was fine. at that point the car was well apart so I decided to do the head gasket.....every thing went good. the gasket looked to be the problem. Ran it yesterday and it still over heats


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## wolfen1086 (Oct 4, 2007)

electric fan maybe not turning fast enough or not at all


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## troy deppen (Dec 27, 2010)

The fan does not come on till 220. witch is what i was told it was supposed to. I took the thermostat out the car will not over heat. remember I replaced it 3 times. I guess I'm going to drain all coolant and flush it for a few hours and try another thermostat. All coolant in system is new so I don't get it. Bought two from oriely and one from auto zone. I tested one in boiling water and it opened. Idea's??


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## SABL (Jul 4, 2008)

Thermostat removed and engine doesn't overheat?? I know years ago it was possible to install a thermostat backwards but don't think it can happen nowadays. The pellet/spring must point towards the engine block. 

When I was a youngster I only installed the thermostat in my '57 Chevy in the winter......for heat. Maybe run the Cobalt for a few days without the T-stat to help flush the cooling system??


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## wolfen1086 (Oct 4, 2007)

Yes its possible now days to put one in backwards now days, but it usually requires a hammer and the IQ of a dead rat.LOL


If the thermostat is makin it over heat make sure they are giving you the correct thermostat, I don't know about where you are but here there's one parts store that gave me the wrong one in the right box


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## kendallt (Feb 21, 2007)

check lower radiator hose. Sometimes when they get old they will collapse and restrict coolant flow.


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## kendallt (Feb 21, 2007)

SABL said:


> Thermostat removed and engine doesn't overheat?? I know years ago it was possible to install a thermostat backwards but don't think it can happen nowadays. The pellet/spring must point towards the engine block.
> 
> When I was a youngster I only installed the thermostat in my '57 Chevy in the winter......for heat. Maybe run the Cobalt for a few days without the T-stat to help flush the cooling system??


 running without a thermostat should be considered emergency/temporary measures only. UNLESS you drive 50+ miles each time you start it, going without one for any length of time will reduce engine life because the engine doesn't get warm enough to boil moisture and other contaminants out of the oil.


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## SABL (Jul 4, 2008)

Same thing goes for when I make the 1 mile trip to the local carry-out. That's why I don't shut the engine off until I get back home.....most times I also go around the block, which equates to adding another 3 1/2 miles to the trip.


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## Wrench97 (May 10, 2008)

Usually it means there is air trapped in the system on newer cars, does the thermostat have a bleed hole to allow air to pass through?

Try filling the radiator then pulling the top hose and fill it.


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