My 300 TDI has around 150k miles and a few months ago I noticed some pressure in the crankcase not enough to blow out the dipstick but it definitely blows out of the filler cap along with smoke/oil mist. I changed the filter for the breather and removed the pipes and blew through them to check for blockages. After this I assumed either a problem with valves or piston rings but recently I noticed I am losing coolant about 1 pint per fortnight there are no coolant leaks and no sign of coolant in the oil however once I noticed steam from my exhaust so im assuming head gasket, the whole block is bathed in oil. Would a head gasket cause combustion gasses to enter the crankcase? Apreciate any replies