Defrost out with no hot air

MANDYWENTZEL82

MEMBER
1999 CHEVROLET VENTURE
140,000 MILES

Why is it when I turn on the defrost my van starts out with hot air then the air turns cold and it starts to overheat? As I am driving down the road a while my temp gage goes to hot and my water light will come on and the heat will turn to cold of I keep going and turn the heat off then the temp gage will slowly climb back down to cold and the water light will turn off? I recently had the thermostat changed and 2 relays changed and still the same problem. I have also had the temperature sensor changed and now when I turn the van on the temp gage goes straight to hot

Sunday, January 15th, 2012 AT 10:24 PM

2 Replies

FIXITMR

MECHANIC
9,990 POSTS

Sounds like you are LOW on coolant. Make sure radiator is full and overflow bottle is at proper levels.

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Sunday, January 15th, 2012 AT 10:28 PM

FIXITMR

MECHANIC
9,990 POSTS

Also note this. The lack of heat along with temp guage fluctuations are common symptoms of head gasket failure. Accompanied by coolant loss, they can also be symptoms of intake gasket failure, a problem you are guaranteed to have if your Venture is pre-2003 (I'm not sure in which modle year GM fixed it, but it was still a problem in 02). You are especially prone to the intake gasket problem if you operate in cold climates.

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Sunday, January 15th, 2012 AT 10:35 PM