Cabin heater not working - 2L SE Avant 55

[Naseem]

Hi all,

Some of you might remember that I had problems with my A4 a while ago. It's finally been fixed after a load of work (cambelt, water pump, thermostat, head-gasket, rad). The problem all started with the cabin heater not working, just blowing out cold air.

The engine overheating and coolant leak has now been sorted, but I'm left with the initial problem again of the cabin heater blowing cold. At times, randomly after driving a while it'll blow warm for a few mins then go cold again.

If everything else has been replaced and the heater matrix is flushing clear, what could the problem be? I'm tempted just to get the matrix changed, but a bit hesitant as it's a big dash removal job isn't it? I did read somewhere a while ago that the matrix can be removed via the drivers foot-well behind the console fairly easily, although I can't find that information anymore.

Someone suggested that it might be the Climate control panel playing up; I know I can hear the flaps moving when I change temp from cold to hot so they're not stuck.

Any ideas before I change the matrix?

[Naseem]

Just a quick update, I heard back from the garage yesterday and they've confirmed again that it's definitely not the matrix. After the rad had fixed the overheating problem, I had the car back for a week or so before it went in again for the heater matrix. Over these few days the car had a little trouble starting as if it was

As Ii mentioned above they've confirmed it's not the heater matrix, but the cylinder casing has worn out apparently, causing a loss of pressure hence the coolant isn't reaching the heater matrix and warming up the cabin. He's ordered some 'special' additive to run through the engine and is hoping that will cure it. He said coolant needs to be drained first, additive mixed with water and engine run for about 20mins, drained again and usual coolant replaced.

Not sure what to make of all this. Yet more money, tried selling and no-one wants to buy either!