heat ups & downs...

[kboat]

Can someone please tell me what could be the cause for my 4.0's heat to drop while sitting still at idle speed but heating up during driving?

 

[2000RR4EVER]

Same problem with my 00RR. Someone please shed some insight.

 

[rjkingston]

Does anybody know?

I have the same problem, and keep throwing money at it.

 

[chunter]

Is problem that you have with your heating system? I have a 99 disco w/30k on it. The heating system started cooling when at idle and took forever to heat up. Thsi was because the there was not enough coolant in the motor. My car goes into the shop tomorrow. It has a coolant leak that I can not find. In 8 months it has leaked 3/4 of a gallon of coolant. The engine still looks brand new and spotting a coolant leak should be easy. I smell coolant sometimes however none on the ground and I can not find any when I crawl under the motor and look inside. Does anyone have any suggestions?

 

[rjkingston]

I have full fluid, new thermostat, relay, etc, etc. I think a pressure test on yours will find the leak.

 

[joey]

Try to back flush your heater core and see if this helps... sometimes the junk will build up in the heater core... a good back flush may help.

 

[chunter]

My problem was the intake manifold leaking at 30k. $500 later and then wait to see what happens next!!!!