Expert: Sean Halliday - 12/20/2008

Question
hi iv got a L reg BMW 318i and she runs fine and does not over heat and does not lose water and iv checked the dipstick and thats fine too but when i check the cap after a run(about Half&hour)there's coolant and oil mixture on the cap which at first i thought head gasket but she runs fine What do you think.Cheers

Answer
Its condensation build up.Thats with most high mileage bmws and also volvo have the same thing on the older 240s and 740s.I would suggest changing to a synthetic oil as its better for the engine.As with all engines there will be condensation in the crank and it will find the easiest way out,the filler cap as the crank breather is one way only through the pcv valve.Fit a new pcv and make sure the crank breather is clear and the problem should be a lot less.Regular oil changes as well,synthetic will be every 6000,miles.