GM Caprice 1990-1993 Repair Guide



All vehicles are equipped with independent front and rear brake systems. The systems consist of a power booster, a master cylinder, a combination valve, front disc assemblies and rear drum assemblies.

The master cylinder, mounted on the left firewall or power booster, consists of two fluid reservoirs, a primary (rear) cylinder, a secondary (front) cylinder and springs. The reservoirs, being independent of one another, are contained within the same housing; fluid cannot pass from one to the other. The rear reservoir supplies fluid to the front brakes while the front reservoir supplies fluid to the rear brakes.

During operation, fluid drains from the reservoirs to the master cylinder. When the brake pedal is applied, fluid from the master cylinder is sent to the combination valve (mounted beneath the master cylinder), here fluid pressure is monitored and proportionally distributed to the front or rear brake systems. Should a loss of pressure occur in one system, the other system will provide enough braking pressure to stop the vehicle. Also, should a loss of pressure in one system occur, the differential warning switch (located on the combination valve) will turn ON the brake warning light (located on the dash board).

As the fluid enters each brake caliper or wheel cylinder, the pistons are forced outward. The outward movement of the pistons force the brake pads against a round flat disc or brake shoes against a round metal drum. The brake lining attached to the pads or shoes comes in contact with the revolving disc or drum causing friction, which brings the wheel to a stop.

In time, the brake linings wear down. If not replaced, their metal support plates (bonded type) or rivet heads (riveted type) will come in contact with the disc or drum; damage to the disc or drum will occur. Never use brake pads or shoes with a lining thickness less than 1/32inch (bonded brakes) or 2/32inch (riveted brakes).

Most manufacturers of disc pads provide a wear sensor, a piece of spring steel, attached to the rear edge of the inner brake pad. When the pad wears to the replacement thickness, the sensor will produce a high pitched squeal.