Overheats when driving only. I thought maybe it had a blow head gasket?

JC-842

MEMBER
2000 CHEVROLET CAVALIER
2.2L
4 CYL
2WD
AUTOMATIC
43,000 MILES

Overheats when driving only. I thought maybe it had a blow head gasket because I had white smoke from the exhaust. No oil in the oil pan. Drained and changed oil.
So I thought maybe an intake manifold gasket. Poured Blue Devil in top radiator hose. Smoking stopped immediately. Water pump replacement was done one week later. It was leaking. Now the car overheats only when driving. Idles for a long time like an hour and no overheating. Fan was repaired also. Water disappears from reservoir. No leaks under the car. Car sat up for a long time only has 43,000 original miles. My son without my knowledge poured a bottle of Barr's stop leak in reservoir. This I know is a bad idea from past experience. I'm wondering if maybe the radiator is stopped up because it doesn't run hot at idle only on the highway. It appreciate any help you can provide.
And I also checked for rusted and leaking freeze plugs. Nothing. Thank you. JC

3 Replies

KASEKENNY

MECHANIC
18,907 POSTS

I think you may have been on the right path with the head gasket. So we need to prove this out or not so we can move on. Here is a guide that will help:

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

Once we know for sure if the head gasket is ok then we can move on but with the coolant disappearing but there are no leaks means it is getting burned.

https://www.2carpros.com/articles/engine-overheating-or-running-hot

Let us know with this info and we can go from there. Thanks

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Thursday, July 8th, 2021 AT 11:07 AM

JC-842

MEMBER
181 POSTS

I think I may have describe the issue incorrectly, I apologise. The the coolant is not being burned it is coming out of the overflow hose on the coolant tank/reservoir. After driving for several miles I'll say 15 miles the temperature starts climbing. And the water is being forced out of the reservoir. You can refill it and continue driving. I'm thinking the radiator/heater core are clogged from the Barr's stop leak my son added to the radiator before we realized the water pump was bad.

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Thursday, July 8th, 2021 AT 11:08 AM

KASEKENNY

MECHANIC
18,907 POSTS

Oh. I understand. Yes. You may be correct. This is normally one of two things that cause that.

First is as you mentioned there is a restriction causing the coolant to boil and force back to the reservoir.

The other possible cause can still be a head gasket that is pressurizing the cooling system. So you can still check using this blue fluid as shown in this guide. This will check for hydrocarbons in the cooling system. The fluid should stay blue and not get lighter in color or even turn yellow.

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

I would start with the head gasket check because if this is ok then you can start flow checking the systems and look for a restriction.

You can also use a laser temp meter to look for cool and hot spots in the cooling system and engine but flow checking is more accurate.

https://www.2carpros.com/articles/how-to-use-an-infrared-temperature-meter

Also, the heater core hoses should feel about the same temp or you can use the meter.

Let us know what you find with this.

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Thursday, July 8th, 2021 AT 11:08 AM