2007 Chevy Uplander, While at idle the heater blows cold, but while vehicle in motion heater works properly.

2007 CHEVROLET UPLANDER
78,000 MILES
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FSR
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The heat can be turned up all the way and while you sit in driveway or idle at a light or in traffic it blows cold, but while you are driving weather its 25 or 50 it blows hot. The coolant is new and full and I see no leaks from hoses or other areas but that dosent mean their not there. I was wondering if it was thermastat or waterpump. Maybe some other bigger problem? Any idea appreciated.
Nov 22, 2011 at 4:28 PM
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ASEMASTER6371
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i would lean more toward a clogged heater core.
make sure the coolant level is correct.

Roy
Nov 22, 2011 at 4:29 PM
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CHEVYAM01
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I just took my 2007 Uplander in for the same problem and it found out that the system was air locked. Once they got all the air out of the coolant system, the coolant was able to flow. Now we have HEAT! They also checked the doors inside the duct work to make sure they open and close properly. This can be done with a scanning tool.
Dec 1, 2011 at 5:09 PM
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WES123
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Had the same issue with our 2007 Uplander. You need nee head gaskets. There is air getting into the cooland system. This all happened to me in the last few weeks. We are also getting a new tanny and rad because coolant leaked into the transmission. Good luck with yours.

Feb 5, 2012 at 12:33 PM
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RASMATAZ
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It will do that if the water pump impeller is on its way out-
Feb 5, 2012 at 1:30 PM
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HENRYR79
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How do you know if all of the air is out of the system and how do you go about getting it out?
Oct 29, 2012 at 1:59 AM
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T. ALMOND
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Jan 1, 2023 at 5:47 AM