header tank overflow

[fuzzy]

the overflow pipe on my headertank is spraying coolant out, i can blow and sook easily through it , should it have some sort of valve to prevent the coolant escaping so easily? i still have the e30 header tank fitted with the cosworth engine, its not the headgasket being knackered causing excess pressure as i have a multilayer stainless steel wrc headgasket fitted. some one says the cap should have a yellow tag on it as they were replaced as the original ones where prone to knackering, is this true as i dont have a yellow tag?

[Simon]

The expansion tank cap should have a yellow/orange disc on the underside, this indicates it has been changed under a BMW re-call.

IIRC, the tank cap when at the correct pressure releases excess coolant through the overflow system, I would pop to your local dealers, hand over your chassis number, and they should give you the correct cap, give this a go, and please come back and let us know if it worked!

[Brianmoooore]

Problem with the original cap was excess pressure, popping hoses, heater matrixes and radiator ends, not no pressure.
Are the two O rings on the cap OK?

[fuzzy]

they seem to be ok, the pressure seems to be escaping through the cap forcing the coolant out,when the cap is on i can blow and sook easily through the overflow pipe with no resistance.