heat, no heat, burping the coolant

I see a few of us have had this problem: no heat at idle or low rpms, heat is ok when the rpms are raised to at least 2500-3000. Most of you have replaced components like the water pump, T-stat, or tried things like flushing the heater coil and hoses (a commonly recommended solution). But the cheapest, and maybe the most logical seems to be from J cAT to simply "burp" the cooling system via the expansion tank. Sadly, after his suggested repair, NO ONE HAS RESPONDED TO SAY WHETHER IT WORKED OR NOT :(.

My 2005 1500LT with 121,000 miles has developed the same problem. The whole pump, T-Stat, belts and all were replaced at 97,000 miles for the exorbitant cost of over $650 (my wife was stuck 600 miles away on a Sunday). We have not had any heat or a/c issues at all until this past winter. The issue is the same as the other posters: no hot air at idle, warm or hot air when rpms are raised to 2500+ rpms AND HELD. Air blows cool again if the rpms drop below 2000-2500+.

My first repair response was to check the "heater control valve", which this burb DOES NOT HAVE (no matter what the parts houses say). So, at this point I'll try J cAT's solution. I will give a response with what happens afterwards.

yes the air purge procedure can fix it ... sometimes a very small leak can cause this or changing the coolant ..

if they do not reply doing this procedure , then they fixed it ....

yes the air purge procedure can fix it ... sometimes a very small leak can cause this or changing the coolant ..

if they do not reply doing this procedure , then they fixed it ....

When I removed the tank cap it gave a nice "sigh" that showed it was holding pressure as designed. It's pretty cloudy, so I can't really see the level very well from the outside, but I could tell it was a little low. I used a long rod to test the depth, and it showed to be near the cold level "low" line. But when I started and ran the engine the level dropped to about 3/4" from the bottom....without the heater on yet. I could only find about a pint of coolant, added some dist water, and put that into the tank. It didn't raise the level very much, but it seems to have made the heater work after running it at the 2000+ rpm for a few minutes.

I'll know better after I go buy some more coolant and fill the tank to proper level.

clean up the plastic pressure tank use a pool cleaner .. for vinyl .. then keep checking when cold on level ground for continued loss of coolant.. this may be the water pump gaskets .. try to tighten the WP bolts...

I would go to Auto Zone or Advanced Auto and get a loaner pressure with the system full put about 12 psi on the gage. Leave it on for a few minutes look for leaks. If nothing is noted start engine if the pressure gage pulsates look for a head gasket leak.

I would go to Auto Zone or Advanced Auto and get a loaner pressure with the system full put about 12 psi on the gage. Leave it on for a few minutes look for leaks. If nothing is noted start engine if the pressure gage pulsates look for a head gasket leak.

I haven't seen any evidence of a leak on outside surfaces, so I might just do the pressure test....in case. Thanks

clean up the plastic pressure tank use a pool cleaner .. for vinyl .. then keep checking when cold on level ground for continued loss of coolant.. this may be the water pump gaskets .. try to tighten the WP bolts...

I'll check those. I did fill the tank to the proper level and give the heater a try, but it wasn't very cold outside, nor did I drive the Sub anywhere to check what it does on the road -- yet. But, so far it seems to work properly.