Pontiac Repair: No heat when stopped, head gasket leak, intake manifold gasket

Question
Recently my 2002 Pontiac Montana will only give heat when I am excelerating, as soon as I come to a stop or take my foot off the gas the air turns to cold. Sorry I don't know the engine size.
Thanks!

Answer
Hi Erin:

That's okay those vans all have the same engine size. 3.4 liter V6. My guess is the van is low on coolant. Either the lower intake manifold gasket is leaking coolant or it has a head gasket leak or a water pump leaking. It's 1 of the 3 that's the cause. Take it to a shop and have the cooling system pressure tested and My bet it's on of the things I mentioned leaking. If it is a head gasket or an intake manifold gasket while they are repairing it have them replace the thermostat while their in there doing the repair. I'd get it fixed sooner rather than later because if it's indded low on coolant you'll go from n oheat inside the van to the engine overheating which is not a good thing at all! Good luck :}