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1998 Chevy Cavalier Heater problem. No heat. Head gasket?

Tiny
DPLOGGER
  • MEMBER
  • 1998 CHEVROLET CAVALIER
  • 4 CYL
  • 2WD
  • AUTOMATIC
  • 13,000 MILES
Dear Carpro expert,
My cavalier recently stopped blowing warm air out of the heater vents. I had the heater core replaced some time ago when it leaked inside my car. After that it seemed to work fine. Now it is not heating. I've had the hoses checked on the heater core and switched them to see it it was the problem. My car seems to blow out a little warm air untill it hits 45mph. Then cold. A local auto mechanic says it could be a cracked head or blown head gasket. There are no leaks anywhere, and there is no antifreeze in the oil. Do you think it is the head gasket or cracked head? Thanks for your response and I appreciate your time.

Darren
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Wednesday, January 21st, 2009 AT 6:30 PM

4 Replies

Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 109,885 POSTS
Darren:

I doubt that the head gasket is the problem. Try something for me. With the engine running, hot, and the heater on high, feel both heater core hoses under the hood. Both should be hot. Let me know what you find. Also, make sure the coolant level is full.

Joe
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Wednesday, January 21st, 2009 AT 7:27 PM
Tiny
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  • 3 POSTS
I checked both hoses are hot at idle and antifreeze is at the correct level. WHen I hit 45 mph the air coming from the vents becomes cool and the temp. Guage drops below the normal operating temp. THis also occurs when I hold the rpm's around 3,000 for a few minutes. A new thermostat was installed and I even tried running it without a thermostat for diagnostic puposes and it did the same thing. So I don't think it is the thermostat/switches/or heater core because of this. The only thing I can think of is a blown head gasket?
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Sunday, January 25th, 2009 AT 8:56 PM
Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 109,885 POSTS
Hi:
It tryly sounds like you got a bad t-stat. To me it sounds like it's sticking open. When you start driving, the eng will cool faster which should cause the t-stat to partially close restricting coolant to the engine. But you say the temp drops; which indicates it's till wide open. The same with the high idle. Try the T-stat.
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Monday, January 26th, 2009 AT 10:18 AM
Tiny
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Ok, I will try changing it again. Maybe it was a defective one I last put in. I will let you know if this fixes my problem.

Thanks,
Darren
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Monday, January 26th, 2009 AT 11:10 AM

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