C4 Tech/Performance L98 Corvette and LT1 Corvette Technical Info, Internal Engine, External Engine

Overheating?

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Old Jul 5, 2011 | 10:31 PM
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Default Overheating?

1989, no mods, 108,000 + miles.
Overheated 1600 miles ago and blew head gasket. Heads machined, valves done, new radiator. Low coolant light came on few days ago and I burped it. Took back to shop they said possible air bubble or low coolant sensor going bad but couldn't find anything wrong. Drove her 350 miles over the weekend.
Only outstanding issue is that left side muffler is loose and needs replacing.

Today went out for a drive and b4 I got 1/2 from home I noticed temp just climbing steadily to 260. I shut her down and saw that coolant was spilling out of the the overflow tank. I added some coolant to radiator and drove home.
Fans are working. Removed & checked the thermostat, seemed to be ok (should've replaced it anyway) and replaced radiator cap. Took it for a drive and no issues.
Can anyone suggest anything else I should check? Any chance the hanging muffler could cause this. I've also noticed the mpg is slightly down but have been attributing this to the muffler.

Last edited by gunnerjuju; Jul 5, 2011 at 10:59 PM. Reason: added info
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Old Jul 5, 2011 | 11:22 PM
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Has it done anything bad since you replaced the radiator cap? It sounds like that could have been a problem. If you fill your engine with cold water, as it expands it overcomes the pressure rating of the cap and flows into the overflow tank. As it cools the vacuum formed by the cooling antifreeze solution sucks water back into the engine.

If your cap were leaking there would be no vacuum to refill the engine. Since it's done it before there was probably water in your overflow tank and the new water just was too much and it overflowed. If it still does it you may need to have your cooling system pressure tested.
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Old Jul 5, 2011 | 11:27 PM
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I only drove it about 2 miles after I replaced the cap. I will drive it some more tomorrow and "report" back. I appreciate your input.
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Old Jul 6, 2011 | 06:36 AM
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Check the front air dam.

Maybe you sucked up a plastic bag and it's blocking the radiator.

It happens more often than you might think.

My issue was 5 leaves the size of my hand.

Almost totally blocked the front of the radiator.
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Old Jul 6, 2011 | 07:15 AM
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Fill the system full. Pull the overflow hose off the tube on the rad neck. Bring it up to operating temp and see if and at what temp you get any coolant out the tube. In my car the rad cap inner gasket didn't make a good seal on the rad neck. The system wouldn't build any pressure. Only reason I found the problem was because I installed a remote fill and saw the water flowing out the overflow tube while I was topping off the system. Doesn't cost anything but a little time to check this out.
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Old Jul 7, 2011 | 11:45 AM
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since replacing the radiator cap I've had no overheating issues. I did take it in to be compression check etc and they told me everything was ok.
Thank you all for your input

Last edited by gunnerjuju; Jul 7, 2011 at 11:46 AM. Reason: spelling
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