F 350 4WD Pickup V8-351 5.8L VIN H EFI (1997)
Brake Proportioning/Combination Valve: Description and Operation
Brake Master Cylinder
The brake master cylinder fluid control valve regulates the hydraulic pressure in the rear brake system. It is located on the brake master cylinder and is
screwed into the rearmost outlet port. When the brake pedal is applied, the full brake fluid pressure passes through the brake master cylinder fluid control
valve to the rear brake system until the valve's split point is reached. Above its split point, the brake master cylinder fluid control valve begins to reduce
the hydraulic pressure to the rear brakes, creating a balanced braking condition between the front and rear wheels to minimize rear wheel lockup during
hard braking.
In case of front brake system malfunction, the brake master cylinder fluid control valve has a bypass feature that allows full hydraulic pressure to the rear
brake system.
