Mk111 Heater Problem 'help'
 

All of a sudden the heater on my MK111 has stopped heating....air con is ok, cooling system is ok [new water pump recently fitted] and temp gauge keeps a perfect average. I know it could be an air lock but has anybody else out there had a similar problem and what's the best way to dissipate an air lock please. [also head gasket is ok]
Pete.

The water valve may gone into an 'off' mode. If the vacuum diaphram in it has a hole, it won't allow hot water to get to the core.

The vsv with it may be bad. Check to see if the valve works. By-pass the vsv with the vacuum hose hooked directly to the heater water valve. (its on the firewall, heater water hoses hook into it).

The vsv goes bad with age. I just removed mine, and run vacuum to the water valve in the fall/winter/early spring. Then I remove it and plug a golf tee into the vacuum line for the late spring/summer.

my heater went out to leaks anti freeze in the floor board mines the heater core