Brake Proportioning/Combination Valve: Testing and Inspection

FUNCTION TEST

Connect Pressure Gauges To Proportioning Valve:

1. Connect two pressure gauges, one each to the input side and output side of the proportioning valve, as shown.
2. Air bleed 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.

Measuring Output/Input Pressure:

a. Output pressure begins to drop relative to input pressure (split point). The standard value is 2.70 - 3.19 MPa (391 - 462 psi).
b. Ensure that output fluid pressure is at the standard value when the pedal pressure (input fluid pressure) is increased. The input fluid pressure standard value is 6.86 MPa (996 psi). The output fluid pressure standard value is between 3.92 - 4.41 MPa (569 - 640 psi).
c. Output pressure difference between left and right brake lines should be 0.4 MPa (57 psi).
4. If the measured pressures are not within allowable ranges, replace the proportioning valve.

FUNCTION TEST

Connect Pressure Gauges To Proportioning Valve:

Measuring Output/Input Pressure:

a. Output pressure begins to drop relative to input pressure (split point). The standard value is 2.21 - 2.70 MPa (320 - 391 psi).
b. Ensure that output fluid pressure is at the standard value when the pedal pressure is increased. The input fluid pressure standard value is 6.07 MPa (925 psi). The output fluid pressure standard value is between 3.19 - 3.68 MPa (462 - 533 psi).
c. Output pressure difference between left and right brake lines should be 0.4 MPa (57 psi).
4. If the measured pressures are not within allowable ranges, replace the proportioning valve.