TRIUMPH 2000 COOL RUNNING

Q

I have a problem with the heater on my 1974 Triumph 2000 Mk2. The engine temperature rises to the normal running mark as it always has and the coolant does appear to be circulating as it should; this in my mind would indicate that the water pump and thermostat are fine. My problem is that the coolant does not appear to be flowing through the heater pipes, and even when the engine is up to running temperature and the radiator and hoses are hot, the heater inlet hose remains cold. I have already checked the heater valve and this is in the open position.

If I remove one of the heater hoses with the engine running I can encourage the coolant to flow through the heater, but after a couple of minutes this will go cold again, which indicates to me that for some reason the flow from the engine is insufficient to push the coolant around the heater. Any ideas of what I should do next?

Alan Winters

AI would have said that the heater matrix had become blocked over time and this was the cause for the poor flow, but as you have confirmed that the coolant does freely flow through the system when one of the hoses is disconnected, this would not appear to be the case.

I would check that the thermostat you have fitted is set to open at 82°C and not the 74°C which is available; this slight difference may make an improvement. I would also ensure that the heater return pipe on the engine has been replaced with the stainless steel version. It may well be the case that if the old steel pipe is still fitted, this inside diameter has been greatly reduced by corrosion and deposits lining the inside of the pipe. This would have the result of reducing the flow sufficiently to stop the coolant travelling through the heater matrix and instead opting for an easier route.

Finally, it may also be worth checking the impeller on the water pump, just to ensure that this hasn’t corroded away, reducing its performance. If all else fails I would recommend bleeding the system using a pressure tester to ensure any airlocks in the system are forced out.