Recently purchased a 92 940 Turbo with 146K. (I ought to know better . . . adding it to my 88 740 GLE and 95 940 Turbo Wagon.) The car runs fine but the brakes are an issue. The car stops but brakes go right to the floor. Mechanic has replaced the master cylinder (didn't fix the problem) and just went over the car again. There's no fluid leak at all but some kind of air leak in the system (from the rear) but they can't find it. Has a Bendix brake booster. They could try replacing the brake calipers for another $400 but won't guarantee that will fix the problem. Unfortunately, I'm not much of a mechanic and mine is scratching his head. I've already dumped a lot of money into this car but am ready to give up. Any ideas for what to look for? Thank you!