Heater Problems
 

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.
Pete.

Under the hood on the firewall there is a vacuum operated servo that opens the heated water to the heater core. Check to make sure that is working. The heater vents might not be oopening either.

Purging the air takes a little time, but when it is cool you can take the heater hose off where it goes into the servo on the firewall and run some water through the pipe with a water hose to force the air out of the core. Take the radiator cap off while doing this. If you can take the other hose off the other end of the heater core you can tell if it is clogged or not by how much flow of water comes out. Another thing is to pull the upper radiator hose off and hold it up while blocking off the thermostat end and pour water in the hose till it comes out the radiator, put the cap back on and then put the hose back on. Make sure your overflow reservoir is half full at least and that the radiator cap is good.

Let us know how it goes.

Russ

Got some insight and more questions.
 

Having the same problem. I can hear the heater servo vent open in the firewall as i adjust the climate control but I still get no heat. I have actually narrowed the problem down to the heater valve that Russ is talking about. Mine is recieveing vacuum but i'm not sure its recieving enough because it doesn't open. Could the In car sensor be telling the climate control that its already hot in the car, i don't think this is the problem because the climate control cuts the A/C once the car starts cooling off inside so i'm guessing the sensor is good. Any guesses on mine? Also since i'm hear, does the solar sensor just up the A/C when you face into the sun? Could my water temp switches be telling the car its not warm enough yet so don't open the heater valve? The repair manual doesn't really even discuss the valve on the firewall so i don't know quite what to do.