What was found
AFTER LANDING AND SLOWING TO TAXI SPEED, THE FLIGHT CREW WERE UNABLE TO MAKE A RT TURN TO EXIT THE RUNWAY DUE TO THE LOSS OF BRAKING ACTION OF THE RT BRAKE. THE AIRCRAFT WAS STOPPED AND THEN REMOVED FROM THE RUNWAY USING A TOW TRACTOR. MAINTENANCE INSPECTED THE AIRCRAFT AND FOUND BRAKE FLUID LEAKING FROM THE NR 3 AND NR 4 BRAKE HOUSINGS. THE UNITS WERE DISASSEMBLED AND THE O-RINGS WERE FOUND TO BE IN AN EGG SHAPE. THE O-RINGS WERE REPLACED WITH NEW UNITS AND THE AIRCRAFT WAS ABLE TO BE RETURNED TO SERVICE. THE O-RINGS ARE SUSPECTED TO BECOME EGG SHAPED DUE TO EXCESSIVE HEAT BUILDUP, ONE SUSPECTED CAUSE IS THE FLIGHT CREWS TAXING TO THE RAMP, SETTING THE PARKING BRAKE AND LEAVING IT SET. THIS DOES NOT ALLO