Master Cylinder - BENDIX/DELCO-Moraine

All master cylinders are dual-piston, single-bore assemblies. When the brake pedal is depressed the master cylinder primary piston moves forward. Under normal conditions, the combination of hydraulic pressure and the force of the primary piston spring move the secondary piston forward at the same time.

When the pistons have moved forward so that their primary cups cover the by-pass holes, hydraulic pressure is built up and transmitted to the front and rear brake assemblies.

Some master cylinders have a residual pressure valve installed under tube seat insert in drum brake outlet. This valve keeps a small amount of pressure in drum brake systems and prevents air from entering system.