My heater on my disco 2 blows out cold air unless vehicle is moving. I am very concerned about this because last time this happened the head gaskets went out. I just got them places 2 years ago. Can they possibly be going out again? I've checked my coolant and it is full, and the disco has not overheated since two years ago when the gaskets went bad.

 

Could be the heater core if it is clogged it take more pressure to move the water through it. It could also be the water pump if the impeller is going you get less flow at lower RPM.

Are the hoses going to the heater core hot - both of them ?

Do you know your engine temps or just use the dash gauge ?

 

I only use the gauge on the dash, how can i check the actual engine temp?

 

You can buy a device called a scan gauge or ultra gauge.

https://shop.advanceautoparts.com/p/...E&gclsrc=aw.ds

UltraGauge OBDII Scan tool & Information Center

It is very easy to install: you just plug it into the OBDII under the dash. Takes about 2 min. You should be seeing temps around 188-204.

 

If you're getting heat while the engine is running at higher rpm...then most likely it's a flow issue...not temp issue. Obviously, you have a high enough engine temp to give you heat (while moving), so it is either a partially plugged heater core or water pump or blockage somewhere else. Most likely...heater core...especially, if you don't know previous history of vehicle and what's been dumped in the cooling system over the years (stop leak product)...or if it has sat for a long period of time. Remove both hoses and back flush the heater core...would be the best place to start.

 

 

I'm pretty car illiterate. How can I flush the heater core out? Any how to or diagrams?