VEHICLE DESCRIPTION: SCHOOL BUSES EQUIPPED WITH BOSTROM DRIVER'S SEAT MODEL F222 OR BOSTRUM "ROUTEMASTER" SEAT. BLUE BIRD OPTION 2821 OR 2824. THE SEAT PEDESTALS ARE FATIGUE CRACKING ADJACENT TO THE WELD WHICH SECURES THE PEDESTAL'S UPPER PLATE TO THE UPPER, TELESCOPING PORTION OF THE ADJUSTABLE COLUMN SUPPORT.
Consequence & remedy
Consequence: THE UPPER MOUNTING PLATE AND SEAT UPPER GRADUALLY BECOMES LOOSE RESULTING IN THE UPPER PLATE DETACHING FROM THE SUPPORTING COLUMN AND THE SEAT CAN FALL FROM ITS MOUNTING. THIS CAN RESULT IN PERSONAL INJURY TO THE DRIVER.
Remedy: DEALERS WILL REPAIR THESE PEDESTALS WITH A NEWLY DESIGNED PEDESTAL BRACKET KIT.
A SUDDEN HYDRAULIC PRESSURE LOSS DURING HARD TURNS RESULTS IN A MOMENTARY LOSS OF POWER STEERING ASSIST. THE PRESSURE LOSS OCCURS WHEN THE HYDRAULICALLY DRIVEN ENGINE COOLING FAN TURNS OFF IN THE TURN.
Consequence & remedy
Consequence: THE DRIVER REACTS TO THE LOSS OF POWER STEERING ASSIST BY OVERSTEERING, WHICH COULD RESULT IN A VEHICLE ACCIDENT.
Remedy: THE HYDRAULIC CONTROL VALVES WILL BE REPLACED WITH VALVES OF A NEW DESIGN. UNTIL SUCH TIME AS PARTS ARE AVAILABLE, OWNERS WILL BE INSTRUCTED TO DISCONNECT THE FAN CUTOFF SWITCH SO THAT HYDRAULICALLY DRIVEN FANS WILL RUN FULL TIME, ELIMINATING THE PRESSURE SPIKE.
AIR BRAKE SUPPLY LINES ARE REVERSED AT THE BRAKE TREADLE VALVE. THIS CAN CAUSE THE MODULATED SPRING BRAKE FEATURE ON THE REAR AXLE BRAKE TO BE INOPERABLE. IN THE EVENT THE REAR BRAKE SUPPLY RESERVOIR WERE LOST, THIS COULD RESULT IN LOSS OF BRAKES WITHOUT PROPER FUNCTION OF THE MODULATED SPRING BRAKE ACTION OF THE REAR BRAKE AXLE TO STOP THE VEHICLE.
Consequence & remedy
Consequence: LOSS OF THE SECONDARY SPRING BRAKE FUNCTION COULD RESULT IN A VEHICLE ACCIDENT IF THE PRIMARY AIR BRAKES FAIL.
Remedy: VEHICLE OWNERS WILL BE INSTRUCTED TO SWAP SUPPLY LINES AT THE TREADLE VALVE TO OBTAIN THE CORRECT PLUMBING, AND WILL BE REIMBURSED FOR LABOR EXPENSES.
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