Disco 1 No heat

For some reason I have no heat coming from my vents on my 300tdi disco.
I recently had the head re-done and assumed that I had an air lock in the heater matrix so flushed the coolant and made sure the matrix had water flowing through it. This brought the heating back for all of a day. Parked up at a stupid angle (uphill) to make sure that the header tank was higher than the heater matrix and ran the engine with the thermostat bung out for a bit - this got the heaters hot again but has only lasted a week or so before they go cold again.

I'm not losing any coolant but I've recently had the canaries return to living under my bonnet.

I'm swaying towards the water pump being on it's way out - with the thermostat bung out and the engine running I would expect that water would gush out of the thermostat - but it just gently bubbles, only gushing out if I take the lid off the expansion tank.

Does this sound like the water pump is on it's way out or am I barking up the wrong tree?

If the water pump impeller has become detached or the bearing has failed you would know by the noise coming from the pump, so that just leaves the shaft lseal failing which if it did u would see by the coolent leaking below the pump... So dose that sound like the water pump to you?
Do u have the heater matrix hoses fitted the correct way round?.

Sent via my iPad Air on a train.

Before the head was done where the heaters OK if so the head gasket has not sealed and is leaking compression gases into the coolant water way and will airlock the heater.

mr glee said:

Before the head was done where the heaters OK if so the head gasket has not sealed and is leaking compression gases into the coolant water way and will airlock the heater.

Click to expand...

Hmm, I did have heat before the HG change - and did have heat after the HG change for a week or so. Even after a long drive I don't have any noticeably different to normal pressure build up in the header tank - which I would have expected if exhaust gasses were getting in the coolant again.

Having had a furtle last night, I noticed that if I run the engine for a while with the heaters set to cold and then turn them back to hot I get a brief blast of toasty hot air which then slowly cools to warm air. I'm now leaning towards a partial blockage in the heater matrix which squeezing the pipes temporarily solved. I think a job for this weekend is to try and flush the heater matrix.

Does anyone know which way the flow goes through the matrix? I'm assuming that the return from the heater matrix is the one that flows across the top of the head in the metal pipe and not the one that comes from the back of the head?

Quick update.... maybe premature but having removed the hoses from the heater matrix at the weekend and attached a hose to the return pipe and flushed the system I (touch wood) appear to have regained heat again. Currently running with the heater on full (even in this heat!) just to keep an eye on it but 100 miles or so later and I still seem to have heat....

U have an air blending heater system so why have the dampers turned to hot? hot or cold it makes no difference to the flow through the matrix.

Anyway, it seems u have removed any air that was present in the matrix.

discool said:

U have an air blending heater system so why have the dampers turned to hot? hot or cold it makes no difference to the flow through the matrix.

Anyway, it seems u have removed any air that was present in the matrix.

Click to expand...

Not knowing the ins and outs of how the coolant flows through the heater matrix I can only assume that the brief period of heating I was experiencing after turning the dial from cold to hot was purely down to the trapped air in the matrix heating up.
Another bonus at the moment is that both sides of the car seem to be as hot as each other whereas before the passenger side was noticeably cooler.

It was still hot on my drive into work this morning - so fingers crossed I've got to the bottom of it.