ANTI-LOCK BRAKE SYSTEM
1986-87 BRAKES
Ford Motor Co. Anti-Lock Brake System
Ford; Thunderbird (1987)
Lincoln; Continental, Mark VII
* PLEASE READ THIS FIRST *
NOTE: Ford Motor Co. uses the Teves designed anti-lock brake system.
DESCRIPTION
The Teves 4-wheel anti-lock brake system is a compact integral power brake system that uses brake fluid for both the braking function and hydraulic boost. The system is divided into 3 circuits with individual front brake circuits and a combined rear brake circuit. Major component parts of system are the master cylinder and hydraulic booster, electric pump and accumulator, valve body assembly, electronic controller, reservoir, relays and 4 wheel sensors.
OPERATION
MASTER CYLINDER & HYDRAULIC BOOSTER
The master cylinder and brake booster are arranged in the conventional fore and aft position with the booster behind the master cylinder. The booster control valve is located in a parallel bore above the master cylinder centerline and is operated by a lever mechanism connected to the brake pedal push rod.
ELECTRIC PUMP & ACCUMULATOR
The electric pump is a high pressure hydraulic fluid pump that runs at frequent intervals for short periods. This high pressure fluid charges the hydraulic accumulator that supplies the service brake system.
The accumulator is a gas filled pressure chamber that is part of the pump and motor assembly. The electric motor, pump and accumulator assembly are mounted to the master cylinder/booster assembly.
VALVE BODY ASSEMBLY
The valve body contains 3 pairs of solenoid valves, one pair for each front wheel and a 3rd pair for both rear wheels combined. The paired solenoid valves are inlet/outlet valves with the inlet valve normally open and outlet valve normally closed. The valve body is bolted to the inboard side of master cylinder/booster assembly.
RESERVOIR WITH FLUID LEVEL WARNING SWITCHES
The reservoir assembly is a translucent plastic container having 2 main chambers. Integral fluid level switches are part of the reservoir cap assembly with 2 electrical connectors, one from each end of the cap, for wiring harness connections.
There are 2 low pressure hoses leading from the reservoir. One hose attaches to the hydraulic pump assembly and the other hose to the master cylinder housing. The reservoir is mounted to the hydraulic unit with a screw and bracket and a push in tube outlet that seats in a grommet located in the brake booster housing.
WHEEL SENSORS
There are 4 variable reluctance electronic sensor assemblies. Ford Motor Co. uses 104-tooth ring. Each sensor is connected to the electronic controller through a wiring harness. The front sensors are bolted to brackets located on the front wheel spindles.
The front toothed sensor rings are pressed onto the inside of the front rotors. The rear sensors are bolted to brackets which are bolted to the rear disc brake axle adapters. The toothed rear sensor rings are pressed on the axle shafts, to the inside of the axle shaft flange. Each sensor has an adjustable air gap between the sensor head and tooth surface.
ELECTRONIC BRAKE CONTROL MODULE
The Electronic Brake Control Unit (EBCM) is a self contained non-repairable unit consisting of 2 microprocessors and the necessary circuitry for their operation. These microprocessors are programmed identically.
The controller monitors system operation during normal driving as well as during anti-lock braking. Under normal driving conditions, the microprocessors send short test pulses to the solenoid valves that check the electrical system.
Wheel lock conditions trigger signals from the EBCM that open and close the appropriate solenoid valves and open the main valve which supplies pressure to a reaction sleeve. This results in moderate pulsations in the brake pedal accompanied by a change in pedal height. During normal braking, the brake pedal feel will be identical to a standard brake system.
SYSTEM OPERATION
The hydraulic pump maintains a pressure between 2030 psi (143 kg/cm) in the accumulator and is connected by a high pressure hose to the booster chamber and a control valve.
When the brakes are applied, a scissor-lever mechanism activates the control valve. Pressure, proportional to the pedal travel, enters the booster chamber. This pressure is transmitted through the normally open solenoid valve through the proportioning valve to the rear brakes.
The same pressure moves the booster piston against the master cylinder piston, shutting off the central valves in the master cylinder. This applies pressure to the front wheel through the 2 front normally open solenoid valves. The electronic controller monitors the electromechanical components of the system.
Malfunction of the anti-lock brake system will cause the electronic controller to shut off or inhibit anti-lock brake system. However, normal power assisted braking remains. Malfunctions are indicated by one or both warning lights inside vehicle. Loss of hydraulic fluid or power boost pressure will disable the anti-lock brake system.
The 4-wheel anti-lock brake system is self monitoring. When the vehicle ignition switch is placed in the "RUN" position, the electronic controller will perform a preliminary self check on the anti-lock electrical system. This is indicated by a 3-4 second illumination of the "Check Anti-Lock Brakes" light.
During vehicle operation, including normal and anti-lock braking, the electronic controller continually monitors all electrical anti-lock functions and many hydraulic performance characteristics.
In most malfunctions in the anti-lock braking system, the "Check Anti-Lock Brakes" and/or "BRAKE" light will be illuminated. The sequence of illumination of these warning lights combined with the problem symptoms determine the appropriate diagnostic tests to perform.
SERVICING
BLEEDING
Front Brakes
The front brakes can be bled in the conventional manner, with or without the accumulator being charged.
Rear Brakes
Bleeding the rear brakes requires a fully charged accumulator or they must be pressure bled using a pressure bleeder attached to the reservoir cap opening, with a minimum of 35 psi (2.5 kg/cm).
Bleeding System With Accumulator Charged
1) Once accumulator pressure is applied to system, rear brakes can be bled by opening rear brake caliper bleed screws for 10 seconds at a time while holding brake pedal in applied position with ignition switch in "RUN" position.
2) Repeat until an air-free flow of brake fluid has been observed at each caliper and then close bleed screws. Pump brake pedal several times to complete bleed procedure. Adjust brake fluid level in reservoir to "MAX" level with a fully charged accumulator.
CAUTION: Care must be exercised when opening rear caliper bleeder screws, due to extremely high pressure available from a fully charged accumulator at bleeder screws.
Bleeding System With Pressure Bleeder
1) When using a pressure bleeder, the bleeder must be attached to reservoir cap opening and a minimum of 35 psi (2.5 kg/cm) must be maintained on system. With brake pedal released and ignition off, open rear caliper bleeder screws for 10 seconds at a time.
2) Once an air-free flow of brake fluid has been observed at each caliper, close bleed screws and place ignition switch in "RUN" position. Pump brake pedal several times to complete bleed procedure. Siphon off excess fluid in reservoir to adjust level to "MAX" level with a fully charged accumulator.
REMOVAL & INSTALLATION
* PLEASE READ THIS FIRST *
CAUTION: Before servicing any component which contains high pressure, it is mandatory that the hydraulic pressure in the system be discharged.
HYDRAULIC UNIT
Removal
1) Discharge system pressure by turning ignition off and pumping brake pedal a minimum of 20 times until an increase in pedal force is clearly felt.
2) Disconnect battery ground cable. Disconnect electrical connectors from reservoir cap, main valve, solenoid valve body, pressure warning switch, the hydraulic pump motor, and ground connector from master cylinder.
3) Disconnect brake tubes from solenoid valve body one at a time. Immediately plug each threaded tube opening in the valve body to prevent fluid loss. Do not allow brake fluid to come in contact with any of the electrical connectors.
4) To disconnect hydraulic booster push rod from brake pedal, inside passenger compartment, disconnect stop light switch wires at connector on brake pedal. Remove hairpin connector at stop light switch on brake pedal and slide switch off pedal pin far enough for switch outer hole to clear pin.
5) Remove switch using a twisting motion, being careful not to damage switch. Remove 4 retaining nuts at dash panel. From inside engine compartment, remove booster from dash panel.
Installation
1) Mount hydraulic unit with rubber boot to engine compartment side of dash panel, with 4 mounting studs and push rod inserted in proper holes. From inside passenger compartment, loosely start 4 retaining lock nuts on hydraulic unit studs.
2) Connect push rod-to-brake pedal connecting pin. Install inner nylon washer. Align push rod yoke and bushing on brake pedal and slide pin through yoke and brake pedal. Slide stop light switch onto brake pedal connecting pin until switch outer hole is completely on pin. Install outer nylon washer and secure assembly with hairpin retainer.
3) Install stop light switch connector to switch. Tighten 4 hydraulic unit lock nuts to 13-25 ft. lbs. (18-34 N.m). In engine compartment, connect solenoid valve body brake tubes one at a time starting with rear brake tube (tube to right front wheel), while removing plugs.
4) Connect electrical connectors to hydraulic reservoir cap, main valve, solenoid valve body, pressure warning switch, hydraulic pump unit and ground cable to master cylinder. Be sure all connections are clean and rubber seals are in place. Connect battery ground cable. Bleed brake system.
HYDRAULIC ACCUMULATOR
Removal
1) Discharge system pressure by turning ignition off and pumping brake pedal a minimum of 20 times until an increase in pedal force is clearly felt.
2) Disconnect electrical connection at hydraulic pump motor. Using an 8 mm hex wrench, loosen and completely unscrew accumulator. Make sure that no dirt particles fall into open port. Using an 8 mm hex wrench, loosen and remove accumulator adapter block bolt and remove adaptor block (if necessary).
Installation
1) Before installing accumulator adapter block, if removed, inspect "O" rings for damage and replace as necessary. Be sure "O" rings are in position on either side of adapter block and are wet with brake fluid. See Fig. 6. Install adapter block bolt and tighten to 25-34 ft. lbs. (34-46 N.m).
2) Install a new "O" ring over accumulator screw thread and seat it against shoulder. Screw in accumulator and tighten to 30-34 ft. lbs. (40-46 N.m). Wipe off any excess fluid. Connect hydraulic pump motor electrical connector.
3) Turn ignition on. Check that "Check Anti-Lock Brakes" light goes out after a maximum of one minute. Top off fluid reservoir up to "MAX" mark with a fully charged accumulator.
HYDRAULIC PUMP MOTOR
Removal
1) Discharge system pressure by turning ignition off and pumping brake pedal a minimum of 20 times until an increase in pedal force is clearly felt.
2) Disconnect battery ground cable from battery. Disconnect electrical connections at hydraulic pump motor and pressure warning switch. Using an 8 mm hex wrench, loosen and completely unscrew accumulator. Make sure that no dirt particles fall into open port.
3) Remove suction line between reservoir and pump at reservoir by twisting hose and pulling. To prevent fluid loss, a large vacuum nipple can be slipped over reservoir opening as hose is removed.
4) Remove banjo bolt on pump high pressure line to hydraulic booster housing at housing. Be sure to attach and save the 2 "O" ring seals (one on each side of banjo fitting). Remove 6 mm Allen head bolt attaching pump and motor assembly to extension housing located directly under accumulator.
5) Use a long extension and universal joint from front of hydraulic unit to reach this bolt. Check and save thick spacer between extension housing and shock mount. Move pump assembly inboard (toward engine) to remove assembly from retainer pin located on inboard side of extension housing.
Installation
1) Install pump assembly onto retainer pin and swing pump into position. Install Allen head bolt and thick spacer (spacer between rear shock mount and extension housing flange). Tighten bolt to 5-7 ft. lbs. (7-10 N.m).
2) Install sealing bolt on high pressure line to booster housing under reservoir. Inspect "O" rings and replace as necessary. Be sure that the 2 "O" ring seals are installed, one on each side of banjo fitting. Tighten bolt to 12-15 ft. lbs (16-20 N.m).
3) Install suction (pump feed) line to fluid reservoir taking care to minimize fluid loss when removing vacuum nipple and installing hose. Install a new "O" ring over threads of accumulator and seat it against shoulder of hydraulic accumulator. Wet "O" ring with clean brake fluid. Screw in accumulator and tighten to 30-34 ft. lbs. (40-46 N.m).
4) Connect pump motor and pressure warning switch electrical connectors. If installing a dry pump, pump and brake system must be pressure bled. Connect battery ground cable. Turn on ignition.
5) Check that "Check Anti-Lock Brakes" light goes out after a maximum of one minute. Top off fluid reservoir up to "MAX" mark when the accumulator is fully charged.
RESERVOIR ASSEMBLY
Removal
1) Discharge system pressure by turning ignition off and pumping brake pedal a minimum of 20 times until an increase in pedal force is clearly felt.
2) Disconnect battery ground cable from battery. Remove electrical connectors on reservoir cap. Unlock and remove bayonet type cap. Empty reservoir of as much brake fluid as possible using a large syringe or suction pump.
CAUTION: To prevent fluid contamination, it is mandatory that any
syringe or suction pump used to empty reservoir be clean and used only for brake fluid. Do not reuse brake fluid. Use new fluid only.
3) Disconnect suction line between pump and reservoir from reservoir, by twisting and pulling hose at reservoir fitting. Remove return line between reservoir and master cylinder housing at reservoir in same manner.
4) Remove 4 mm Allen head reservoir mounting screw. Pry reservoir from booster housing. Check to be sure that short sleeve and "O" ring are removed from booster grommet hole.
Installation
1) Install reservoir mounting bracket in its guide on bottom of reservoir. Check to see that spacer sleeve and "O" ring are in place on reservoir. Wet inside of reservoir grommet with brake fluid.
2) Insert reservoir into grommet on booster housing as far as it will go, being sure sleeve and "O" ring are in place. The reservoir should be held vertical to booster during installation.
3) Secure mounting bracket to booster housing with Allen head screw. Tighten screw to 35-53 INCH lbs. (4-6 N.m). Install return and pump feed hoses onto reservoir fittings as far as they will go. Fill reservoir to "MAX" line and bleed brake system.
4) Top off reservoir to "MAX" line with a fully charged accumulator. Install reservoir cap and connect electrical connectors. Reconnect battery ground cable.
ELECTRONIC BRAKE CONTROL UNIT
Removal
Disconnect 35-pin electronic connector from EBCU. Remove 3 retaining screws holding electronic controller to bracket and remove controller.
Installation
Install EBCU assembly to bracket. Connect 35-pin electrical connector to control unit. Be sure connector is properly snapped into position. Install trim panel.
PRESSURE SWITCH
Removal
1) Discharge system pressure by turning ignition off and pumping brake pedal a minimum of 20 times until an increase in pedal force is clearly felt. Disconnect battery ground cable from battery. Disconnect solenoid valve body 7-pin connector.
CAUTION: Failure to remove connector can result in damage to connector if pressure switch wrench handle slips and strikes connector.
2) Remove pressure switch using Pressure Switch Socket (T85P-20215-B), a 1/2" to 3/8" adapter, and a 3/8" ratchet.
Installation
Before installing pressure switch, inspect "O" ring and replace as necessary. Install pressure switch using pressure switch socket. Tighten pressure switch to 15-25 ft. lbs. (20-33 N.m). Connect solenoid valve body connector. Connect battery ground cable to battery.
FRONT WHEEL SENSOR
Removal
1) From inside engine compartment, disconnect sensor electrical connector from right or left front sensor. Raise vehicle and disengage wire grommet at right or left shock tower and pull sensor cable connector through hole.
2) Use care not to damage connector. Remove sensor wire from bracket on shock strut and side rail. Loosen 5 mm set screw holding sensor to sensor bracket post. Remove sensor through hole in disc brake splash shield. See Fig. 6.
3) To remove sensor bracket or sensor bracket post, in case of damage, caliper, hub and rotor assembly must be removed. After removing hub and rotor assembly, remove 2 brake splash shield attaching bolts which attach sensor bracket. If toothed sensor ring is damaged, replace it.
Installation
1) Install sensor bracket with sensor bracket post (if removed). Tighten post retaining bolt to 40-60 INCH lbs. (4.5-6.8 N.m) and splash shield attaching bolts to 10-15 ft. lbs. (13-20 N.m). Install hub and rotor assembly and caliper.
2) If a sensor is to be reused, pole face must be clean from all foreign material. Carefully scrape pole face with a dull knife so sensor can slide freely on post. Glue a new front paper spacer on pole face (front paper spacer is marked with an "F").
3) Install sensor through brake shield onto sensor bracket post. Be sure paper spacer on sensor is intact and does not come off during installation.
4) Push sensor toward toothed sensor ring until new paper sensor contacts ring. Hold sensor against sensor ring and tighten 5mm set screw to 21-26 INCH lbs. (2.4-3 N.m). Insert sensor cable into bracket on shock strut, rail bracket, then through inner fender apron to engine compartment and seat the grommet.
5) Lower vehicle and from inside engine compartment, connect sensor electrical connection. Check function of sensor by driving vehicle and observing "Check Anti-Lock Brakes" light.