1990 Ford Country Squire Brake Service (ONLINE REPAIR MANUALS)

The vacuum assist diaphragm assembly multiplies the force exerted on the master cylinder piston in order to increase the hydraulic pressure delivered to the wheel cylinders while decreasing the effort necessary to obtain acceptable stopping performance.

Vacuum assist units get their energy by opposing engine vacuum to atmospheric pressure. A piston, cylinder and flexible diaphragm utilize this energy to provide brake assistance. The diaphragm is balanced with engine vacuum until the brake pedal is de...

DESCRIPTION

The proportioning valve (when used),Fig. , provides balanced braking action between front and rear brakes under a wide range of braking conditions. The valve regulates the hydraulic pressure applied to the rear wheel cylinders, thus limiting rear braking action when high pressures are required at the front brakes. In this manner, premature rear wheel skid is prevented.

TESTING

When a premature rear wheel slide is obtained on a brake application, it usually is an indication that the fluid pressure to the rear wheels is above the 50% reduction ratio for the rear line ...

When working on or around brake assemblies, care must be taken to prevent breathing asbestos dust, as many manufacturers incorporate asbestos fibers in the production of brake linings. During routine service operations the amount of asbestos dust from brake lining wear is at a low level, due to a chemical break down during use and a few precautions will minimize exposure.Do not sand or grind brake linings unless suitable local exhaust ventilation equipment is used to prevent excessive asbestos exposure.

The brake shoe and lining assemblies should be replaced if the lining is ...

Whenever new brake components are installed in the hydraulic system, it is recommended that the entire hydraulic system be thoroughly flushed with clean brake fluid.

It may sometime become necessary to flush out the system due to the presence of mineral oil, kerosene, gasoline, etc., which will cause swelling of rubber piston cups and valves so they become inoperative. The procedure is as follows:

Flushing is ...

The caliper assembly consists of a pin slider caliper housing, inner and outer shoe and lining assemblies and a single piston,Figs. and . The caliper slides on two pins which also act as attaching bolts between caliper and the combination anchor plate and spindle. The outer brake shoe and lining assembly is longer than the inner brake shoe and lining assembly. Inner and outer shoe and lining assemblies are attached to the caliper by spring clips riveted to the shoe surfaces. The inner shoe is attached to the caliper by installing the spring clip to the inside of the caliper piston. T...

• Inspect components for damage and unusual wear. Replace as necessary.
• Inspect wheel cylinders. Boots which are torn, cut, or heat damaged indicate need for wheel cylinder replacement. Fluid spilling from boot center hole, or wetness around wheel cylinder ends indicates cup leakage and need for wheel cylinder replacement.A small amount of fluid is always present and is considered normal, acting as a lubricant for the cylinder pistons.
• Inspect backing ...