Overheating

2002 GMC ENVOY
233,000 MILES • 4.2L • 6 CYL • 4WD
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BUYRITEAUTO21
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Vehicle got up to around 260 degrees while driving the other day. It had been driven on the highway for about 40 minutes before the overheating started. I added coolant and drove it for another 40 minutes and the temperature didn’t rise. The heat does not blow warm and there is some white smoke coming out the exhaust. The oil looks good and is not milky brown. What would cause this issue?

Thanks
Nov 14, 2021 at 2:26 PM
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KASEKENNY
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It sounds like you are the beginning stages of a head gasket issue which is what it sounds like you are thinking as well.

Here is a guide that talks about white smoke but add in the overheating or running hot and that is where we need to look first:

https://www.2carpros.com/articles/white-smoke-or-steam-coming-from-the-exhaust-pipe

The fact that you found it low on coolant means we need to find where that cooling is going. If you have no external leaks, then it is most likely being burned in the engine which is the white smoke.

At this point, I would suggest doing the head gasket test shown in this guide:

https://www.2carpros.com/articles/head-gasket-blown-test

This is a chemical test that will show if you have combustion gases in the coolant which is a clear sign of a head gasket issue.

Please run through this info and let us know what you find. Thanks
Nov 15, 2021 at 4:11 PM