Brake Master Cylinder problems of the 2002 BMW 745

Vehicle has a recall for brake vacuum pump 10v-446. Vehicle was brought into a local mechanic and he said the brake master cylinder was not working properly. He did research and said that it was a BMW recall. Finally took vehicle into BMW (tucson) and the said they saw no oil leak, therefore master cylinder would not be replaced. They want to charge $1,175 to fix it. The brake vacuum pump and master cylinder work together. BMW is not fixing the real problem, they are expecting me to fix the flawed brake system. The heat of the engine can burn oil off, so just because they didn't see it, doesn't mean it wasn't there and caused the failure of the master cylinder diaphragm. When the part connected the recall and is faulty, that should be covered. This is a safety issue that BMW is not fixing and allowing vehicles on the road with faulty brakes. They designed the braking system and being such an important part of a vehicle, they should be responsible to fix the problem. All braking parts are original BMW parts.