Power brake servo failure due to water accumulation. Driving the car and attempted to stop when there was suddenly no power brakes. Dealer indicated that it was caused by a bad vacuum line. When replacing the vacuum hose, I found the brakes booster (servo) submerged in 6 inches of water. After draining the water and disconnecting the vacuum hose a large amount of water drained from inside the power booster/servo. Car ran fine after repair. 1 week later, on 1/16/12 during sub-freezing temps, there ws no brake pedal function at all. Extensive web search found several threads devoted to the problem. Here is one of those links: www.bimmerfest.com/forums/showthread.php?T=418457 two potential causes: 1 - the brake booster/servo is in a well. This well does have a small drainage hole that can clog due to leaves or other debris. This well is under a cabin air filter box. The air filter is a normal maintenance item, complete removal of the box and maintenance under the box is not part of standard maintenance. In climates where leaves fall, they can collect under this box and block drainage. Should the well fill with water the unit will become submerged and ultimately take on water. Water seeping into the booster/servo can cause failure of the unit causing brake function to be drastically reduced. If all the water is not drained, in below freezing conditions the water in the booster/servo will freeze, effectively freezing the brake pedal, making braking impossible! this water can also get sucked into the vacuum line and be sucked into the intake manifold and then into the engine potentially causing massive engine failure. 2 - failure of the ccv valve, caused by condensate, can also cause water to ultimately back-up into the vacuum system and into the brake booster/servo, causing the same effects mentioned above. Booster replacement needed.

- East Brunswick, NJ, USA

When applying brakes when wet, brake pedal becomes very hard to push. A squishing sound can be heard as the brake is applied and pedal moves to the floor board. Only happens when brake is very wet (coming out of carwash, also happened a number of times during a hard rain.) took a great deal of effort to push down on brake pedal and bring car to a stop.

- Alexandria, VA, USA