1991 Ford Aerostar Brake Service (ONLINE REPAIR MANUALS)

Two warning lamps are located on the instrument panel to alert the driver to a system malfunction. The red brake warning lamp is used to indicate conventional brake system malfunctions such as low fluid level, parking brake applied and low vacuum conditions (diesel engines only). The yellow anti-lock system warning lamp is used to indicate proper warning lamp circuit operation (2 second illumination with ignition On or engine cranking). If yellow lamp comes on while vehicle is being driven, it is alerting the driver of an anti-lock system malfunction and yellow lamp can...

The rear anti-lock brake system constantly monitors rear wheel speed. In the event of an impending rear brake lockup, the system regulates hydraulic pressure to the rear brakes, preventing total lockup when the brakes are applied and thereby reducing the possibility of skidding.

The system consists of a yellow warning light on the instrument panel, an electro-hydraulic rear anti-lock brake system (RABS) valve mounted on the frame rail behind the crossmember, a speed sensor mounted on the rear drive axle, an exciter ring mounted on the differential case and a comput...

SERVICE BRAKE

The rear brake shoes, Figs. and , adjust automatically when the vehicle is driven forward or reverse and the brakes are applied sharply several times. Manual adjustment is required only when brake shoes are replaced. When adjusting rear brakes, ensure that parking brake is properly adjusted and that equalizer is operating freely.

With Drums Removed

• With drums removed, clean areas where shoes contact backing plate, then apply suitable lubricant to these contact areas, ensuring that lubricant does not contaminate linings.
• Using suitable brake shoe adjusting gauge, ad...

Bleed primary and secondary hydraulic brake systems separately, bleeding the longest line first on each system. Do not allow reservoir to run dry during bleeding operation. Never reuse fluid that has been drained from the hydraulic system.

• Loosen master cylinder to hydraulic line nuts and wrap shop cloths around tubing below fitting to absorb escaping brake fluid.
• Depress brake pedal slowly forcing air trapped in master cylinder out at fitting.
• Hold pedal down and tighten fittings, then release brake pedal. Releasing brake pedal before fittings are tightened will allow air to ...

AEROSTAR

• Disconnect brake warning lamp electrical connector from master cylinder.
• Disconnect hydraulic lines from master cylinder, then remove master cylinder to brake booster retaining nuts and the master cylinder.
• Before installing cylinder, check distance from outer end of master cylinder pushrod to front face of booster assembly using suitable gauge block, Fig. . Pushrod length should be .980-.995 inch. Turn pushrod adjusting screw inward or outward until specified length is achieved.
• Reinstall master cylinder and retaining nuts, reconnect hydraulic lines and brake warni...

All components are serviced as assemblies and should not be disassembled.

COMPUTER MODULE

1990-91 Models

• Disconnect battery ground cable.
• On all models, disconnect wiring harness from RABS module.
• On Bronco II, Ranger and Explorer models, remove module to instrument panel retaining screws behind center of instrument panel.
• On Aerostar models, remove module to instrument panel anti-skid plate retaining screws on lefthand side of engine cover under instrument panel.
• On E-Series models, remove parking brake actuator assembly as follows:
• Loosen adjusting nut at equalizer.
• From inside e...