diesel cooling system...

Post by **soapyjoe** » 09 Nov 2006, 19:21

How long should it take to get all air out of a diesel cooling system? i have bled mine for evermore and still air keeps blowing out. cant see any leaks anywhere, but i have found that i can blow through the expansion cap both ways, is this norm, or is at meant to be a 1 way valve? got a new one on order from vw anyway hoping thats the problem but in the meantime i'll keep exploring! Thanx

Post by **rogbodge** » 09 Nov 2006, 21:04

How long - not long (once thermos opens). Cap on header tank functions 2 ways ie it can suck coolant back in from expansion tank. System takes abt 16 litres!

Post by **Westy.Club.Joker** » 09 Nov 2006, 21:07

The cap should seal itself, you will need quite a bit of pressure to blow through it, as the sytem will be running at quite a high pressure when hot, the cap should only release any pressure and coolant to the expansion tank if it is getting too hot. Try a new genuine VW cap

Post by **Simon Baxter** » 09 Nov 2006, 21:57

Caps are meant to hold .9 to 1.1 bar of pressure.

Chances are that if you remove it and can see 2 poppet valves then its knackered.

If the cap is black, then it's probably knackered.

If it's non genuine then, it's probably knackered.

I check customers caps on services now as you wouldn't believe the amount of caps that don't hold pressure, thats why I always have a healthy stock of genuine caps on the shelf.

Simon.

Post by **soapyjoe** » 10 Nov 2006, 16:11

Thanks guys. the cap is black looks pretty old as well. have got 1 on order from vw should be here tomorrow along with a new t/stat.