I have a 2001 fiesta 1.9 td and have replaced the thermostat and the heater control valve but the heater is still very poor. If you drive the car normally and don't put the heater fan on then heat does come through but the min you put the fan on the heater starts to cool down rapidly and the heater goes stone cold. If you rev the engine to full throttle the heat will start to come through again. I am now wondering if it's the water pump.

Thanks for any help given

Has it always been like this, or have you done something like change the rad water/anti freeze? It could be an air lock in the heater element

It has a;ways been like this and its not getting any better. I have tried everything I can think of but the heater is very poor under load. I am strongly suspecting the water pump. The car temp runs in the middle of temp gauge and never over heats but yet the bottom hose on rad is not as hot as it should be so suspect pump. I know its a git to change as the timming belt needs to be removed.

Thanks

Don't think its the pump mate, or the engine would overheat and judging by the guage its fine.

I still think the problem lies with the heater itself, but may be wrong

Hi Grinfactor

don't know if this helps. but may be worth a look.

all models are affected

PROBLEM

low heater output

heater blows cold at idle

CAUSE

reduced flow of coolantthrough engine oil cooler

REMEDY

renew engine oil cooler

was going to post an attachment but for some reason can't

tom

Thanks guys. I foned the stealers and they want £260 + vat so not an option. I have also read that its possible to bypass the oil cooler and feed the heater direct but not sure if this is wise. I will try the bypass just to see if the problem is with the cooler.

Thanks all

I have the exact same car I think, W reg, 18TD, is urs the same ? Having the same problem, new coolant, thermostat, heater control valve, heater output poor. Just seems like car isnt getting hot. Would be interesting to know if the bypass indicates the oil cooler problem. How r u getting on ?

Hi My car is the 1.9td 2000 on a Y. I bypassed the oil cooler and hey presto the heater is working a treat. Even at idle the heater still blows hot air and only cools as the water temp drops which is perfectly normal. Just hope the oil cooler is ok without getting any water. In this weather I think its not a problem. Thanks evryone for their help its been much appreciated.

wow. So how do you bypass the oil cooler ? any instructions would be much appreciated.

Follow the pipe from the heater matrix down to the oil cooler on the rear of the engine near the bulk head. At the oil cooler the pipe from the heater matrix goes on one side and there is a pipe on the other side which leads away to the radiator. Remove both pipes from the oil cooler and insert a 15mm copper water pipe between the two rubber hoses that you removed from the oil cooler and jubilee clip both ends onto the copper pipe. Top up radiator with anti-freeze and check for leaks. This cured my problem and car is toastie.

Col

many thanks for the info. So, what do you think the bottle neck is at the oil cooler end, is it not letting the coolant through ? I am thinking there must be a reason for letting the coolant pass through there i.e. cool the oil. Am thnking that maybe it needs a flush or something ?