On a small number of school buses, a check valve within the air brake system may not have been assembled correctly. As a result, there could be an air pressure leak if there is a secondary brake circuit failure. This could cause the parking brakes to apply suddenly.
Safety Risk
A parking brake that self-applies while driving could increase the risk of a crash.
Corrective Actions
Blue Bird will notify owners by mail and instruct you to take your bus to a dealer to inspect, and if necessary, replace the SC-3 check valve.