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And finally (at least for now):-
Footbrake valve operating test.
1 Disconnect the airlines to the master cylinder actuator at the footbrake valve and connect an air pressure test gauge to each port.
2 Charge the air system to operating pressure.
3 Fully apply the footbrake and check that the pressures registered on the test gauges are approximately the same as registered on the vehicle gauge.
4 Release the brake pedal and check that the pressures fall immediately to zero on the test gauges.
5 Re-charge the system and gradually apply the footbrake. Check that the pressures registered on the test gauges are within 7 lb/sq in at pressures below 25 lb/sq in and within 5 lb/sq in at pressures above 25 lb/sq in. The pressures should increase with brake pedal effort until they are the same as registered on the vehicle gauge.
6 Check the pressures again while slowly releasing the brake pedal.
Leakage test:-
1 Charge the air system to operating pressure.
2 Smear the footvalve exhaust diaphragm and the dust cover with soap solution and check for leakage. Leakage indicates faulty valve carrier sealing rings or inlet valves and/or seats.
3 Fully apply the brake pedal and again check for leakage from the exhaust diaphragm and the dust cover. Leakage in excess of a one inch soap bubble in five seconds indicates faulty exhaust valves and/or seats, or piston sealing rings, or valve carrier rear sealing ring.
4 Smear the valve body and airline connections with soap solution and check for leakage with the brake pedal fully applied.
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