After driving my new (to me) '97 Boxster from the UK to Spain 3000Kms with no problems at all, a couple of days ago I had a coolant dump from the overflow area after taking it for a "drive it like you stole it" session over the mountains here in Tenerife. I let the car cool then refilled the coolant as per instructions I've found on here. Since I've done this the coolant has dropped by about a cupful every morning when I check it prior to use. I initially thought that it was an odd air bubble finding its way out of the system but after quite a long drive today I went to check the coolant level and noticed that the bleed valve is open on its own from pressure underneath it, now it has cooled it is now closed. There is no water under the carpets and no condensation on the boot lid or in the general area. Soooo is this correct for the valve to open itself and what could of caused the initial dump? I live 6000ft above sea level would the atmospheric pressure difference make any difference? Great forum by the way
