[StubbornPatriot]

The heater in my 220 GTi Turbo is blowing cold air almost all of the time. Sometimes it gets slightly lukewarm and the other day, for just a minute or two, it kicked out a nice blast of warm air . . . . . and then went cold again. The heater valve operating arm moves freely in and out when the knob is turned. I was told by the mechanic who recommissioned it that it had been running with K-Seal in it. It did have a top end rebuild, There are no HG issues and the engine comes up to temperature nicely and stays there. I suspect the matrix may be a bit clogged up, or something is circulating in the water system that occasionally comes free. Before I look at replacing the matrix, does anyone have any other ideas please?

[itcaptainslow]

It’s worthwhile draining the system, and then flushing the radiator, pipes, engine & matrix individually with a low pressure hose. It’ll take a bit of time, but it’ll give you a good indication of where the blockage lies.

Before draining, you could also run a flushing additive through the system - I’ve had mixed success with these, though.

I ended up replacing the matrix on a 106 diesel I had for the exact same reasons, and after going through the above processes.

[James3990]

Drain the coolant, disconnect the rubber pipes and try back flushing the heater matrix.

It’s either blocking up with k-seal rubbish or you have an air lock/possible leak in the unit itself.

A fairly big job to replace the matrix, but not to difficult.

[StubbornPatriot]

To save draining the system, can I clamp up the matrix in and out pipes before disconnecting them and then use a spare bit of pipe to flush it through? Then, if that doesn't work, drain, flush and refill the system.

[itcaptainslow]

To save draining the system, can I clamp up the matrix in and out pipes before disconnecting them and then use a spare bit of pipe to flush it through? Then, if that doesn't work, drain, flush and refill the system.

You could, but if there’s suspicion the matrix is contaminated, it’s well worth renewing the coolant regardless, as this will be carrying contaminants around the system.

The coolant circuit will also need bleeding after being opened, and it’s often easier to bleed after a full drain and slow refill.

[James3990]

To save draining the system, can I clamp up the matrix in and out pipes before disconnecting them and then use a spare bit of pipe to flush it through? Then, if that doesn't work, drain, flush and refill the system.

You could, but if there’s suspicion the matrix is contaminated, it’s well worth renewing the coolant regardless, as this will be carrying contaminants around the system.

The coolant circuit will also need bleeding after being opened, and it’s often easier to bleed after a full drain and slow refill.

+1 to this great advice.

[StubbornPatriot]

Thank you very much, gentlemen. I will be taking that advice. I know the coolant has been replaced twice already (unless the mechanic reused the same fluid the second time, which is unlikely, but possible) and he said he'd given the whole system a good flush through. The car has only done a few hundred miles since then. Is there any particular bleed regime for the T series? It's an engine I'm unfamiliar with, up to yet. Thank you.

[MatthewL]

Mine didn’t work because the sole weld on the bracket on the bulkhead had worked it’s way off. I screwed the bracket to the bulkhead and the cable operated the valve up direct water into the heater. Worth a check although you may have already!