The heater in my 2001 eclipes works ok when RPMs are up, but at an idel it cools right down. I just replaced the thermostat. that mad no differance. Does anyone have a suggestion were to go next.

 

How many miles are on the car and what did the coolant look like when you changed the thermostat?

 

THe car has 125,000 miles on it. The coolant looked fine.

 

the only thing that could cause that issue is a low coolant level, or a giant air pocket.

 

I was thinking the same thing, or possible flow problem.

 

I will try perging the system of air. Would'nt you thing I would have over heating problums if there was a flow issue.

 

If the heater core is partially blocked it would give you issues at idle since the coolant isnt flowing as much as it would be if you were cruising at abt 3-4k rpms. Check the heater hoses that go to the heater core and see if there are hot to the touch.

 

Out of curiosity, you ever get any liquid under the dash on the passenger side?

 

No water under dash. I did check heater hoses, passenger side is hot the driver side is luke warm. I guess it looks like a heater core is in the near future.Any advise on this. I just did the one in my 2003 Dodge Ram. I had to remove the dash to get at that one, I am asuming this will be the same in this case.