I have a 2007 Uplander LT....I purchased it with 80,000k on it and the following winter it just never seemed to pump much heat at idle or when driving. Turns out there was a blockage in the heater corw problem.was fixed and pumped good heat at idle and under while under load. But the heat issue came back within the last few months.I live in canada so no heat during the winter months is an issue especially with kids.I recently topped up my coolant level and heat at idle and under load was great....My Uplander overheated in cold weather and turns out my radiator blew and lost most of my coolant. Just put in a new rad and now the no heat at idle problem has returned...I stop at a red light it blows cold air and under load it returns to heat what is up with these vehicles having this problem very irritating....dont really know what else to do without spending more money especially right before christmas any suggestions....coolant system was flushed aswell with new rad install....

 

you have air in the cooling system. You must vacuum fill this vehicle. pouring it in by hand will leave air pockets trapped in the heater core

 

I put coolant in by hand when i had a leaking rad and it pumped out more heat at idle and under load then it does withe new rad and a professional coolant system flush. is it still possible to get air in the system with a professional coolant flush and refill?

 

Yes, take it back to the professional that did the job and have it properly completed.

 

I am also having this issue with my 2007 Uplander. I just returned home from the auto shop and they said I need a new heater core. I only have 65k miles on it, and I don't see how I could've blown a heater core already.

 

If you had "blown" a heater core there would be coolant leaking in the van.

Hopefully everyone has serviced their cooling system as recommended in the owners manual and you haven't let the system suck air because the coolant reservoir went empty.

Be sure you have a fresh supply of Dex-Cool in your cooling system and the air has been bled from the system correctly.

 

verify that the shop pressure tested the cooling system and the system was leaking. if there was no leak and they are replacing it because they think its causing the no heat at idle; go elsewhere.

 

If you guys are having problems with your rear heat we need to all call this number and put it under your GMC VIN # and complain. I called today and they said there were no other complaints regarding rear heat in the uplanders. Mines an 08 and had to be flushed twice in the past year. Dealer keeps saying air in the lines. Clearly it's not if so many people are having problems.

Number is 18002633777 and follow the promtps.