Brake Proportioning/Combination Valve: Testing and Inspection

PROPORTIONING VALVE FUNCTION TEST





1. Connect two pressure gauges, one each to the input side and output side of the proportioning valve, as shown.
2. Bleed the air in the brake line and the pressure gauge.
3. While gradually depressing the brake pedal, make the following measurements and check to be sure that the measured values are within the allowable range.





1. Output pressure begins to drop relative to input pressure (split point).





Standard value:

2. Check to be sure that the output fluid pressure is at the standard value when the pedal depression force is increased so that the input fluid pressure is 9.81 MPa (1422 psi).





Standard value:

3. Output pressure difference between left and right brake lines.
Limit: 0.39 MPa (56.9 psi)
4. If the measured pressures are not within the permissible ranges, replace the proportioning valve.