I'm pretty sure the head gasket has gone on my 2002 640 Adventure -- coolant vanishes if I push it hard and get an insta-overheat; also bubbles rising in radiator with cap off. Is there a way to check if it's head or base gasket? I'm looking at doing the head gasket myself - there's very little info on this topic (unless I missed it in search?). Is it relatively straightforward (have a copy of factory manual) ... what's the chance of warped head? Should I leave this to a workshop? I generally work on my bike myself, but not done something this major. I have also had LOTS of really miserable experiences with agents, workshops, etc, so would prefer to do it myself. I recently replaced the seals on the water pump shaft and resealed tappet cover, which fixed the one coolant disappearing problem (and mayonnaise in oil) and a oozing oil leak.