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Old Oct 5, 2023 | 02:54 PM
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Default C5 cooling system

Need advice on what else could be wrong with my C5 base model, car constantly overheats but after it’s turned off and sits for a couple minutes goes back to normal operating temp. Keep finding air in the cooling lines, even after constantly “burping” the system. Just recently replace all the fluid as well as the water pump and thermostats with a 186 thermostats. I know it’s not the fans because they both turn on when temp hits the correct temperature.
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Old Oct 5, 2023 | 04:18 PM
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One of the things it could be is a bad head gasket, it's allowing combustion gases to enter the cooling system, I hope I am wrong and it's not that.
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Old Oct 5, 2023 | 04:24 PM
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Originally Posted by mmartinez
One of the things it could be is a bad head gasket
Not a fun contemplation, but at least there is a test set for that, and you might be able to borrow one from Autozone.
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Old Oct 5, 2023 | 04:27 PM
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Originally Posted by mmartinez
One of the things it could be is a bad head gasket, it's allowing combustion gases to enter the cooling system, I hope I am wrong and it's not that.
wouldn’t that change the color of the coolant though, I always thought the coolant and oil would end up mixing together?
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Old Oct 5, 2023 | 04:34 PM
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I have had several fan motor failures, but one time it was just that the radiator needed cleaning.
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Old Oct 5, 2023 | 06:08 PM
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Originally Posted by HunterM
wouldn’t that change the color of the coolant though, I always thought the coolant and oil would end up mixing together?
Not always a change in coolant or oil color. Depends where the gasket fails, and how badly it has failed. I would certainly exhaust every other option until you are 100% certain it is a head gasket issue, though it doesn't sound good at this point. Do you have bubbles coming up to the top of expansion tank, that don't stop unless the engine is shut off?
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Old Oct 5, 2023 | 07:16 PM
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The air pockets come out when I burp the system, and it’ll run great for the next day or two, temps sit around 205-215 but after the second day temps will shoot up to 240 or so and if I burp the system again a bunch of air pockets will come out
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Old Oct 5, 2023 | 09:26 PM
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Time for a compression test. If you have a bad head gasket you'll probably find two cylinders next to each other with lower compression than the other six.
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Old Oct 5, 2023 | 09:47 PM
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Originally Posted by Dads2kconvertible
Time for a compression test. If you have a bad head gasket you'll probably find two cylinders next to each other with lower compression than the other six.
The beauty of the blown head gasket test kit is it just requires removal of the reservoir cap. Compression may still have to be checked, but I tend towards the low hanging fruit first.
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Old Oct 6, 2023 | 11:37 AM
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Originally Posted by HunterM
The air pockets come out when I burp the system, and it’ll run great for the next day or two, temps sit around 205-215 but after the second day temps will shoot up to 240 or so and if I burp the system again a bunch of air pockets will come out
Best way to burp the system is to elevate the front end at least a couple of feet above the rear end. Leave the cap off the tank, start the car and use varying rpms for a couple of minutes. Make sure the thermostat is open. But if this doesnt work, probably a head gasket.....
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Old Oct 6, 2023 | 01:24 PM
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Originally Posted by HunterM
Need advice on what else could be wrong with my C5 base model, car constantly overheats but after it’s turned off and sits for a couple minutes goes back to normal operating temp. Keep finding air in the cooling lines, even after constantly “burping” the system. Just recently replace all the fluid as well as the water pump and thermostats with a 186 thermostats. I know it’s not the fans because they both turn on when temp hits the correct temperature.
Did a radiator pressure test and found fluid leaking from the hose that connects to the top of the reservoir where it meets the radiator, glad it’s more than likely not a bad headgasket
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Old Oct 7, 2023 | 02:35 PM
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Originally Posted by HunterM
Did a radiator pressure test and found fluid leaking from the hose that connects to the top of the reservoir where it meets the radiator, glad it’s more than likely not a bad headgasket
I had a heater hose that leaked due to a tension hose clamp that lost its tension. Glad you figured it out....
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