Just replaced exp. tank, no leak but steam coming out of air filter area



Hi, help!

BMW 300i 2001

I just had the expansiontank replaced by BMW dealer, it had broken. Drove for 200 highway miles with no problem. Drove for another few in town and steam started to come out of front, by air filter area, and ran out of coolant…

Left it parked last night after refilling coolant, no leak, still full.

What’s wrong?

any help will be appreciated so I have an idea when I take it back to another dealer.


Are you really sure the air filter is involved? I know that on my Mercedes the coolant is circulated to odd places such as the washer fluid tank. A hose leak might emit steam from just about anywhere underhood. Try to replicate the problem and then pinpoint the source. You may just have a bad hose which you can replace yourself.


Could the steam have been from the radiator cap? Or maybe the hoses going to the expansion tank? You will have to identify the area of leak.