erm head gasget???

hi guys im experiencing what seems to be a blown head gasket, but id just like to check with you guys before i take the head off… there is air building up in the top rad hose, the car overheats when running at 3000rpm+ for more than 5 mins (but then goes down again after another one minute? but in traffic its fine?) and ive got no gook in the oil, ive got brownish coolant but no real gook! any suggestions? or am i gonna have to remove the head :cry:  cheers bob…

Are there any signs of water escaping in the engine bay? The fact you mention the problem occurs at higher revs and is ok at idle could mean coolant escaping under pressure and starving the engine of coolant?

Cheers