1990 Ford E-150 Econoline Brake Service (ONLINE REPAIR MANUALS)

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...

Normal hydro-boost units will produce certain noises that current technology cannot correct. These noises occur when brake pedal is manipulated in a manner not associated with everyday braking habits. Normal operating noise can be a hissing, clunk, click or a chatter.

If above normal pedal efforts are applied, the hydra-boost unit will emit hissing noises. These noises will be particularly noticeable with the vehicle motionless and will increase in intensity as pedal efforts increase and system operating temperatures increase. Loud hissing noises at or below normal pedal effo...

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...

SYSTEM COMPONENT LOCATIONS

Refer to system component locations, Figs. through , whenever diagnosis is required. Always disconnect the battery ground cable whenever checking resistance values within the system.

INSTRUMENTATION CHECKS

Brake System (Red) Warning Lamp

To check brake system warning lamp, turn ignition key to the Start position. The red warning lamp should glow momentarily. The warning lamp will also illuminate if the parking brake mechanism is not fully released. If warning lamp fails to glow, service of the electrical system is indicated. If warning lamp illu...

The hydra-boost power brake booster is serviced as a unit.

REMOVAL

• With engine off, depress brake pedal several times to discharge the accumulator.
• Remove master cylinder from brake booster and position up and out of the way. Do not apply booster with master cylinder removed.
• Disconnect three hydraulic lines from booster, then disconnect input pushrod from brake pedal assembly, Fig. .
• Remove booster mounting nuts, then remove booster from vehicle. Do not carry booster by the accumulator and be careful not to drop booster on the accumulator. The snap ring on the accumulator shou...

BRAKE DRUMS

Any time brake drums are removed for brake service, braking surface diameter should be checked with a suitable micrometer at several points to determine if they are within the safe oversize limit stamped on the brake drum outer surface. If braking surface diameter exceeds specifications, the drum must be replaced. If braking surface diameter is within specifications, drums should be cleaned and inspected for cracks, scores, deep grooves, taper, out of round and heat spotting. If drums are cracked or heat spotted, they must be replaced. Minor scores should be remove...