we have a 2001 land rover disco 2 series. it has had over heating issues. the heat does not work unless the car is running with higher rpms, when your on the gas. It seems like the coolant is not flowing at all. we took apart the whole cooling system and flushed it with a hose in various sectoins but we did the whole thing. everything flowwed through perfectly fine and we ran it through for a minute or so on each part. radiator, block, heater core etc. everything ran through fine with no blocks. it has a new thermostat that works and new water pump that works. what could it be??

 

Are you sure the water pump is good?
Does the fan belt make noise?
My bet is on a bad water pump or a loose fan belt, either from the belt being to old of the belt tensioner being bad.

 

New water pump...
Is the belt routed correctly? If the water pump is spinning in reverse, you will have little to no flow, except for high RPMS.

 

Send me your tele number and I'll call you today and walk you thru what to do/check.