2005 Caravan Heat Appears Trapped

We have a new problem with our 2005. The blowers work fine, but are only blowing cold air --except when the engine is taxed a bit / we gun the accelerator. For example, up a really steep hill the heat will suddenly come out of the vents, no problem... for a minute or two, at least, and then it gradually converts back to cold air.

Running up RPMs in nuetral does not create the same result. It only happens when the transmission is enganged. Normal acceleration does not cause warm air to blow.

Any thoughts on what this problem is would be helpful. Thansk a bunch.

It could be a few things.
Low cooling fluid level, air pocket in system, burp it.
Water pump impellers may have corroded away, unlikely unless you have almost 200,000 miles on van.
Radiator may have a leak in it internally, I don't know if that model year has the tranny cooler built inside the radiator. Once the tranny fluid and radiator fluid co-mingle, you might as well junk the van.
2005 models have problems with the upper cooling connection that goes to radiator failing.
If you have rear heat, check the plumbing under van to see if the metal tubes rusted out.
Metal bypass pipe from water pump are known to rust away.
Check the radiator cap.
If your van has many miles on it, maybe the heater core is shot already.
There are many posts about these new vans having stuck flap doors and blinking lights, something about a self diagnosis procedure.

Thanks for the thorough checklist. I Will see what I can find based on that.

I've meant to thank the folks here earlier – My situation was a simple leak in the cooling system. Fixed and filled, all is back to normal.

Thanks for helping a novice like me and sorry for they delay in relaying the outcome. Unfortunately the holidays knocked me off balance for a few weeks.



Happy new year!

Better late than never. Cheers!