oil in expansion tank. astra 1.7 dti isuzu .mk4.d.o.m 2002 ?

Mine is the same mate, and I have also heard of plenty others with the same symptom. I thought the head gasket was knacked at first, but from doing a bit of research, it seems to be just a quirk of this engine. The common thread of advice seems to be to suck the floating oil out every so often (with eg a turkey baster), keep an eye on the engine oil level, and at 6-monthly intervals, remove the header tank, wash with detergent, and flush the cooling system. FYI, mine is still running fine, (touch wood!)

Andy
August 2008