Quote Originally Posted by candellara View Post
I have an update on our Golf as well. The problem reoccurred some time ago - again!!!

Symptoms:

No hot air from vents
On long runs it expels some water from the reservoir
Temp always reads correctly

Anyway, i once again disconnected the heater matrix pipes (which are a bit of a pig to get too) and inserted a pressure hose into the left hand pipe (it won't flush from the right hand outlet as there must be a one way valve somewhere). Anyway i ran the right hand hose initially into a receptical to catch the residue water / dirt in the heater matrix. The coolant that came out of the matrix - was crystal clear with no particles or dirt in it. I then left the hose running for about 20 mins

Re-fitted the hoses, topped up the coolant reservoir and ran the car up squeezing all the hoses whilst i went. Lovely hot air from the vents and the problem has once again gone away

I'm still unconvinced that the matrix is blocking with dirt and maybe getting airlocked? as this poster suggests after the DPF cycle "my idea is that the heater matrix is heated with extreme hot air form the Parkitel Filter just after DPF"
As an append to this, the reason i'm unconvinced the matrix is blocked is that after a simple flush - the heating system works exactly as VW intended. If the matrix was blocked - this wouldn't be the case.

My latest thoughts are that some component is causing air to be ingested into the cooling system - thus causing the heater matrix to airlock (no heat from vents) and the pressurising of the system (water being expunged from coolant bottle after long runs). This seems to only happen after long runs or after a hundred or so miles. When i "flush" the matrix - it expels all of the air, causing the system to work correctly until the next "cycle" when air is ingested into the cooling system

After some reading - EGR cooler? or EGR valve must be suspect. Is this possible?