Vacuum pump full of water

[hugheserj]

My M3 recently started going into limp mode and throwing the error code for vacuum sensor brake booster plausibility. It would only do this on start up from cold and with spirited driving WOT.

I started off by replacing the brake booster sensor last night and that did't fix it. Interestingly, I read a lot of threads that note when the sensor is giving up the the vacuum booster will start running a lot.

I haven't owned the car long but couldn't remember hearing the vacuum pump ever run. So tonight I pulled the pump out and it wouldn't run from a 12V feed.

Opened up the vacuum pump motor and found it was probably half full of water. Cleaned it up dried it out and it ran fine so put it back on the car and no more error codes.

What I can't work out is how the pump motor got full of water???????

[Ximian]

How sure are you it was water? Taste test? I could see it filling up if a line was cracked and was sucking in water from rain or car washes.

I wouldn't drive that car until the brake fluid was flushed and all the lines inspected.