Heater problems

[MarkII16v]

Once the engine is warm they work fine for around five minutes then they start blowing cold air. I can turn them off, slide em back down to cold for 20 minutes or so and then they'll be back to blowing hot air. Seems I can only have warm air for around 5 minutes then it shuts down and replaces it with cooler than usual air. Any ideas as I wanna get it sorted before winter gets here!

[rac030275]

Try replacing the safety bypass valve for the heater matrix. This valve lets water bypass the heater matrix in the event of a leak but sometimes malfunctions stopping the hot water circulating through the matrix. It is located under the bonnet next to the bulkhead where the pipes enter the car. Mine did the same and replacing this part fixed the prob  

[MarkII16v]

Cheers for the tip mate, would it be worth while flushing everything through whilst I'm there? Heard the matrix can get pretty gunked up from time to time.

[rac030275]

I did when I replaced mine and renewed antifreeze at the same time. I used a hosepipe to flush both the input and ouput pipes and a lot of crap came out. I also filled the engine up with clean water and let the engine warm up to give it a futher flush but I am a fussy git so you may not want to do that as well!