K 2500 Truck 4WD V8-379 6.2L DSL VIN C FI (1989)
Brake Master Cylinder: Description and Operation
The master cylinder is designed for a system using low drag calipers. In addition to the standard master cylinder functions, this master cylinder also
incorporates a quick take-up feature in the rear chamber to reduce excessive pedal travel which may result from increased fluid displacement required to
move the low drag caliper piston out against the rotor. The quick take-up uses a spring-loaded ball check valve to hold pressure in the large diameter rear
chamber when the brakes are first applied. At initial application, movement of the rear piston causes fluid to be displaced forward past the primary piston
seal into the primary high pressure chamber. At a specified pressure, the ball unseats and fluid from the large rear bore is displaced past the bore into the
reservoir. When the brake pedal is released, suction generated in the large bore chamber replenishes its fluid supply by drawing fluid from the reservoir
around the quick take-up lip seal and through a small bleed orifice in the ball seat.
