2004 Pontiac Grand Prix No heat when idle

Tiny
ALPHADOGL13
  • MEMBER
  • 2004 PONTIAC GRAND PRIX
Heater problem
2004 Pontiac Grand Prix 6 cyl Front Wheel Drive Automatic 110k miles

My 2004 Pontiac Grand Prix GT2 recently (about 2 weeks) began blowing cool air when the heat is on and idling or sitting at a stop light. When the car is on the express way or in constant motion it blows out heat. What could be the problem?
Monday, January 4th, 2010 AT 10:01 AM

6 Replies

Tiny
JDL
  • MECHANIC
  • 16,098 POSTS
Welcome to the forum, no difference in air flow? It's just a temp issue? Does the engine reach operating temp? Are the heater hoses hot, when the problem occurs? You might need to have the heater core flushed. The flow through the heater core probably slows down at idle because the water pump slows down.
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Monday, January 4th, 2010 AT 10:10 AM
Tiny
ALPHADOGL13
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Thanks for the welcome. No difference in airflow at all. It is just a temp issue. The engine does reach operating temp but I haven't checked the heater hoses yet. Having the heater core flushed sounds like a good idea but I just had the coolant system flushed recently? I thought it might be the thermostat?
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Monday, January 4th, 2010 AT 10:41 AM
Tiny
JDL
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If the problem only happens at idle and the engine reaches operating temp, I don't think the thermostat is the problem. Replacing it shouldn't hurt anything, but, I don't see it.
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Monday, January 4th, 2010 AT 12:28 PM
Tiny
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Thanks! I will do both and see what happens. I'll have the hoses checked as well. I'll let you know the outcome as I'm going to my mechanic today.
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Monday, January 4th, 2010 AT 12:50 PM
Tiny
JUSTASIAM313
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Have you found out wat was going on with your grand prix. Im having the same problem and it is starting to tick me off because I dont do much highway driving there for its always cold in my car.
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Monday, January 11th, 2010 AT 2:48 PM
Tiny
ALPHADOGL13
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I did find out what the problem was. I was told by my mechanic that one of the hoses had a small hole in it and was leaking antifreeze. He replaced all the hoses and the heat has been working fine ever since. That was last week so I suggest you check all your hoses. I haven't had them changed since I got the car in '05 so I think it was time. Let me know your outcome.
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Monday, January 11th, 2010 AT 3:06 PM

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