BMW issued a recall on the X5 model

On certain vehicles, a check valve in the brake vacuum pump may leak a small amount of lubricating oil. Over time, this could result in contamination of the brake booster. Loss of brake power assist could occur which, in conjunction with traffic, road conditions, and driver's reactions, could increase the risk of a crash causing property damage and/or personal injury. Correction: Dealers will inspect and, if necessary, replace the brake booster and master cylinder. Additionally, the brake vacuum line (including the check valve) will be replaced to eliminate the possibility of oil reaching the brake booster.