Brake Proportioning/Combination Valve: Testing and Inspection

Load Sensing Proportioning And By-Pass Valve Components:

Set Rear Axle Load:

1. Set Rear Axle load.
Rear Axle load (include vehicle weight): 1,330 kg (2,932 lbs.)

Install LSPV Gauge:

2. Install LSPV gauge, Special service tool (SST) # 09709 - 29018, and bleed air.

Check Rear Brake Pressure:

3. Raise Front Brake pressure to 7,845 kPa (1,138 psi) and check Rear Brake pressure.
Rear brake pressure: 5,984 ± 589 kPa (869 ± 86 psi).

NOTE: The Brake Pedal should not be depressed twice and/or returned while setting to the specified pressure. Read the value of rear pressure 2 seconds after adjusting the specified fluid pressure.

4. If necessary, adjust fluid pressure.
(a) Disconnect the No.2 shackle from the shackle bracket.

Adjust Length Of No.2 Shackle:

(b) Adjust the length of the No.2 shackle turning it.
Low pressure - Lengthen A.
High pressure - Shorten A.
Initial set: 90 mm (3.54 inch)
Adjusting range: 84-96 mm (3.31-3.78 inch)

NOTE: One turn of the No.2 shackle changes the fluid pressure by about 98.1 kPa (14.2 psi).

Raise Or Lower Valve Body:

(c) In event the pressure cannot be adjusted by No.2 shackle, raise or lower the valve body.
Low pressure - Lower.
High pressure- Raise.
(d) Torque the nuts.
Torque: 13 Nm (9 ft. lbs.)
(e) Adjust the length of the No.2 shackle again.
If it cannot be adjusted, inspect the valve housing.
5. If necessary, check valve body.

Check Valve Body:

(a) Assemble the valve body in the uppermost position.

NOTE: When the brakes are applied, the piston will move down about 1 mm (0.039 inch). Even at this time, the piston should not make contact with or move the load sensing spring.

Check Rear Brake Pressure:

(b) In this position, check the rear brake pressure.
^ With front pressure @ 3,434 kPa (498 psi), rear pressure should be 3,434 kPa (498 psi).

^ With front pressure @ 5,396 kPa (783 psi), rear pressure should be 3,630 to 4,218 kPa (527 to 612 psi).

^ With front pressure @ 9,810 kPa (1,424 psi), rear pressure should be 4,513 to 5,494 kPa (655 to 797 psi).