THE INVOLVED VEHICLES DO NOT CONFORM TO FEDERAL MOTOR VEHICLE SAFETY STANDARD NO. 121, "AIR BRAKE SYSTEMS". THE TWO "O" RINGS THAT ARE SUPPLIED ALONG WITH THE NEW SHUTTLE VALVES ARE OF A BUNA "V" QUALITY. THESE RINGS ARE FULLY FUNCTIONAL IN NORMAL CLIMATE CONDITIONS, HOWEVER, IN EXTREMELY COLD ENVIRONMENTS, SLIGHT LEAKS MAY DEVELOP. THIS VALVE ACTS AS A SEAL BETWEEN THE CYLINDER HEADS OF THE SHUTTLE VALVE AND THE PISTON. IN TIME THIS SEAL MAY EXPAND OR "PUCKER UP", MAKING IT POSSIBLE FOR THE SHUTTLE TO BECOME TRAPPED IN AN EMERGENCY BRAKING SITUATION.
FixTHE DEALER WILL REPLACE ALL DEFECTIVE "O" RINGS WITH ONES HAVING EXTREME COLD RESISTANCE PROPERTIES.