30,000  2007-10 BMW X5 sport utility vehicles with V-8 engines have been recalled with a brake system problem that threatens the safety of the vehicle. The problem stems from a vacuum pump, oil and the booster’s diaphragm.

BMW says the problem is with a check valve of the brake vacuum pump leaking a small amount of oil into the vacuum hose. The oil could contaminate the diaphragm of the boost and cause it to rupture. The oil acts like steak tenderizer and breaks down rubber of the booster.

NHTSA takes this type of failure seriously because it leads to longer stopping distances. Most brake assist systems are designed to work for a few applications after an engine has stalled.

Why does this vehicle have a vacuum pump? In the past decade, engines have become more efficient and vacuum generated by the piston movement does not pull as much vacuum because the air metered by the throttle plate is more accurate to minimize pumping loses.

Should you worry? YES, if the brake booster fails it will take a lot of pedal force to stop an X5.

SOURCE: USA TODAY