Heater problem coolant issue matrix ? HELP

[Leonfrdiesel184]

Hi everyone just wondered of someone could help. Noticed my heater on drivers side is colder compared to passenger. On low fan speed heat better than full blast when its just cold air. I removed the bag from coolant soon as got car bit it was 4 years old at the time. Noticed coolant is getting low and I have had to top up alot recently. I have also noticed what look like a wet patch under the expansion tank like the coolant is leaking but cant see anything visually. Checked cap on tite, but also noticed it was very hard to get off. Checked got any sludge around oil fillet cap all is ok
Is this the heater matrix ? Many thanks for anyone's help in this

 

[BillyCool]

It could be the heater matrix. Assuming you have the TDI, when it does a DPF regen the coolant gets effectively boiled by the lack of water flow through the matrix and exits via an overpressure vent on the expansion tank.

As the system is pressurised, it has to cool down for the coolant level to drop and then you get the low coolant warning the next time you drive it.

You can check the temp of the inlet and outlet pipes to the matrix to see if it's letting the water flow properly.

 

[SuperV8]

As suggested, sounds like your heater matrix.
I also found my cap pressure relief was low - so could be wise to also fit a new tank/cap.
Make sure you flush the system BEFORE fitting the new matrix.