D40 heater flow

[jack.haran]

I recently fitted a YD25 engine in a Navara, I had seen the engine running and it drove fine around some private ground before I bought it. Once fitted and on the first test drive on the open road I saw the temp rise so let it cool and brought it home. Temp gauge didn't go into the red. I replaced the waterpump (properly knackered) and it runs fine now (no overheating) but I cannot get coolant to circulate through the heater. I've flushed the system several times, raised the front of the jeep when refilling the cooling system but to no avail. I temporarily fitted a pump on the output of the heater and could get coolant to flow with it, but once remove it's back to the same old tricks.
Am I missing anything?

 

[tweak'e]

how are you checking there is flow when the engine is going?
are you sure its not a problem with the mix flap?

 

[jack.haran]

how are you checking there is flow when the engine is going?
are you sure its not a problem with the mix flap?

 

[jack.haran]

The pipes in and out of the EGR cooler are hot, but no heat on the inlet to the heater. I’ve flushed the return pipe to the block and the heater itself and all pass fluid easily

 

[tweak'e]

i think you need to check flow first. maybe disconnect return hose and see if engine pumps water out when you start it.
check if water is flowing through egr cooler.
otherwise check the thermostat housing. makes sure there is a thermo stat and check no blockage in the return pipe from heater etc.
quite common for people to screw with thermostats and housings when an engine is overheating.

 

[jack.haran]

Apologies for feeding info here in dribs and drabs. Thermostat and waterpump have been replaced. The thermostat doesn't impede flow through the heater when closed. I removed the outlet pipe from the heater and observed flow from it and was comparable to a pathfinder I have in the yard.

 

[tweak'e]

I removed the outlet pipe from the heater and observed flow from it and was comparable to a pathfinder I have in the yard.

with engine running?
if so that sounds like water is flowing through. therefore most likely cause of the issue is the mix door/flap which allows the air to bypass or go through the heater.

The thermostat doesn't impede flow through the heater when closed.

the reason for mentioning the thermostat is if its stuck open then engine runs cold and the heater doesn't get any heat.