THE POWER BRAKE BOOSTER MAY HAVE BEEN IMPROPERLY MACHINED CAUSING STRESS AND POSSIBLY CRACKS IN THE MASTER CYLINDER WHERE IT IS ATTACHED TO THE POWER BRAKE BOOSTER.
ON THE INVOLVED VEHICLES, THE SELF LOCKING NUTS THAT CONNECT THE LOWER STEERING COLUMN SHAFT TO THE FLEXIBLE COUPLING MAY NOT HAVE BEEN SUFFICIENTLY TIGHTENED. THESE NUTS CAN COME LOOSE.