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+--- Thread: Automatic air bleed valve? (/showthread.php?tid=4403)
Automatic air bleed valve? - Toby - 23-06-2012
Good afternoon all,
Since FCS I have upped boost & fuelling and am now peaking at 28psi.
What I am noticing is that after a hard run the coolant is being pressurised. First thoughts of course are HG issues, however there are no other signs of this (stable running temp etc.)..
I have read on plenty of occasions that high boost pressures can 'lift' the head, momentarily forcing exhaust gases into the coolant system. Could this be what is going on?
I then did some further reading and have found a few 'fixes'.. The most promising one was this guy who fitted an automatic air bleed valve (like the ones found on central heating systems) to the top radiator hose. What this valve does is let out any air/gas whilst not allowing fluid to leak, effectively stopping pressurisation.
Any thoughts? Maybe I should change the HG and perhaps swap to ARP studs.
RE: Automatic air bleed valve? - Jenkosowls - 23-06-2012
Can't really see the need unless pulling serious levels of boost I'm sure darren or ruan will be able to say what sort of pressures cause heads to lift on these. To me if a head is lifting even for a split secound and gases and fluids are mixing the heads gaskets not going to last long. Maybe if you are concearned about the head lifting then you may get away with refreshing the head bolts for oem replacements for sensible boost levels
RE: Automatic air bleed valve? - cwspellowe - 23-06-2012
Sounds like a weak head gasket that's been further breached with upping the boost. Bear in mInd higher temps will warp a head much more easily
RE: Automatic air bleed valve? - Ruan - 23-06-2012
How old is your head gasket, that's typical failure symptoms... I thought it spewed its coolant on the dyno also... I'd bet on general hg failure, you'll never lift the head on a stock turbo... When the head lifts big style you tend to fill the head with air, and it instantly boils over, sort of 110c+...
If its the original gasket, change it, then see what happens, probably be fine for ages...
It's the peak cylinder pressures midrange that f*ck head studs, when you make chronic amounts of torque at lower rpms, the cylinder pressures are mental...
Remember, 28psi on a stock t2 does not equal the airflow of a big turbo at 28psi... My car makes 175hp at 22psi...