Coolant leak

JHARLESS

MEMBER
2007 JEEP LIBERTY
3.7L
6 CYL
4WD
AUTOMATIC
88,000 MILES

I had a mechanic pressure test the cooling system. When he started the engine the pressure started rising pretty quickly. He said this indicated a blown head gasket but it does not make sense to me. The car is not high mileage and has not overheated and runs great. Is it not normal for the pressure to rise when the engine is running? Is that not why it has a vented cap? Thanks for any feedback.

Sunday, August 19th, 2018 AT 9:38 AM

1 Reply

ASEMASTER6371

MECHANIC
52,796 POSTS

Good afternoon.

We do not have vented caps anymore. They are closed systems. When the coolant expands, it raises the level in the surge tank and when it cools it will return to the radiator.

As far as the head gasket, if it builds pressure within a minute or so, then yes, it may be a head gasket leaking compression into the coolant.

The confirmation would be to have a leak down test done. That is where they remove all the spark plugs and inject shop air into each cylinder, one at a time and watch for coolant movement in the radiator.

That will confirm if you have a failed head gasket.

Roy

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

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Sunday, August 19th, 2018 AT 1:37 PM