i was coming up the m5 where my temp gauge started rising gradaully when i come off i pulled over into layby to check it out .
the fans were workinf fine but with the engine off the water hose on top of the rad was sucking itself closed i released the cap on the rad waiting for the explosion but nothing water level was fine but header tank was a bit low but when i undid the oil filler cap the water pipe went back to normal fired the engine up and all was normal again .
just wondered if anyone could shed any light on this all help would be great i didnt know if i had a air lock in the system and if so wheres the bleed screw ?

 

someone else will be able to comment further but I don't think releasing the oil cap should affect the coolant hoses - points to HG failure IMHO.

 

That doesnt sound good tbh, the cooling system is pressurised and should have nothing to do with the oil, if your releasing pressure taking the oil cap off then its either very coincidental or you have gasses between the coolant and oil, that will be a head gasket issue.
I wouldnt drive the car until a decent garage who deal with subaru's has checked it out as the more you drive the more expensive its going to cost, especially if you warp/crack the heads

Tony