TopBanana

Second time this has happened now. Coolant came pissing out of the rad cap. Has all the symptoms of head gasket failure, except there's no contamination in either oil or coolant. Only happens when gunning it. What else could cause this? I'm convinced it wasn't overheating.

It's a long shot, but if the heater matrix was knackered, could this cause enough of a pressure drop to cause the coolant to boil?

Pavlo

If the heater matrix was buggered, it's possible it might upset the flow to the stat, but not sure how or why.

could just be an airlock in system

Paul

harvey

iTrader: (48)

When the heater stops working, unfortunately it is often the precursor to a head gasket overhaul but like Paul says you may be lucky and find it is an air lock. Set heater controls to full hot, top up header tank and reservoir and when it is warm, cane it and see what happens.
Lots of garages have analysis gear that detects gas contamination in the coolant.
Something else to try is a complete coolant change, again with the heater on full red.
Good Luck.

red wrex

yeah i agree with Harvey,

flush the entire system first with some rad flush and then put in a new mixture with the heaters on full heat and blowing out on the second setting

rev it slightly to keep airlocks out and stop it boiling over and after about 5- 10 mins put the cap back on and see how it goes

scoobyboy

probably head gasket, they don't usally mix the oil and water on subarus.just out of curiosity though check the seal where the rubber on the rad cap sits against. did have one where it was eaten away and that had similar problems to yours

TopBanana

Thanks chaps. I shall try flushing it out and refilling first.