Vacuum Brake Booster: Service and Repair
REMOVALCAUTION: Reserve vacuum in the power brake booster must be pumped down (removed) before removing master cylinder from booster. This is necessary to prevent the booster from sucking in any contamination as the master cylinder is removed. This can be done simply by pumping the brake pedal, with the vehicle's engine not running, until a firm feeling brake pedal is achieved.
1. With the engine not running, pump the brake pedal until a firm pedal is achieved (4 - 5 strokes).
2. Remove the primary and secondary brake tubes from the master cylinder outlet ports. Install plugs in the master cylinder outlet ports.
CAUTION: Before removing the master cylinder from the booster, the master cylinder and power brake booster must be thoroughly cleaned. This must be done to prevent dirt from falling into the vacuum booster.
3. Clean area where master cylinder attaches to vacuum booster. Use only a solvent such as Mopar Brake Parts Cleaner or an equivalent.
4. Remove the 2 nuts, attaching master cylinder to vacuum booster.
5. Remove master cylinder from vacuum booster.
6. Remove the 2 structural support struts from bracket above vacuum booster. Loosen the bolts on the other ends of structural support struts and move the struts aside.
7. Remove vacuum hose from vacuum port on intake manifold and check valve on vacuum booster. DO NOT REMOVE CHECK VALVE FROM POWER BRAKE BOOSTER.
NOTE: Removal of the knee blocker trim panel makes access to brake pedal and vacuum booster mounting nuts easier.
8. Remove the steering column knee blocker trim panel from the instrument panel.
9. Locate the vacuum booster input rod to brake pedal connection under the instrument panel. Position a small screwdriver between the center tang on the power brake booster input rod to brake pedal pin retaining clip.
10. Rotate screwdriver enough to allow retaining clip center tang to pass over end of brake pedal pin. Then pull retaining clip off brake pedal pin. Discard retaining clip. It is not to be reused. Replace only with a new retaining clip when assembling.
11. Remove the 2 nuts on the right hand side mounting wiring harness junction connector bracket to vacuum booster studs.
12. Remove the 4 nuts attaching vacuum booster to the dash panel. Nuts are accessible from under dash panel in area of the steering column and pedal bracket.
13. From outside the vehicle, slide the vacuum booster forward until the mounting studs clear the dash panel. Then tilt vacuum booster up and toward engine to remove.
CAUTION: Do not attempt to disassemble the power brake vacuum booster it is to be serviced ONLY as a complete assembly.
INSTALLATION
1. Install the power brake booster on dash panel using reverse procedure of its removal.
2. Install the 4 nuts mounting booster to dash panel. Tighten mounting nuts to a torque of 23 Nm (200 inch lbs.).
3. Install wiring harness junction connector bracket on the right hand side mounting studs of vacuum booster. Tighten mounting nuts to a torque of 29 Nm (250 inch lbs.).
4. Using Lubriplate, or an equivalent, coat brake pedal pin where it contacts vacuum booster input rod.
NOTE: When installing the vacuum booster input rod on the brake pedal pin the input rod must be positioned as shown. The chamfer on the vacuum booster input rod must facing the brake pedal arm when installed on the brake pedal pin. The retaining clip must be installed on the flat side of the vacuum booster input rod.
5. Install input rod for vacuum booster on brake pedal pin.
CAUTION: When installing the brake pedal pin on the vacuum booster input rod, do not re-use the old retaining clip.
6. Install a NEW retaining clip on the brake pedal pin. The retaining clip must be installed on the flat side of the vacuum booster input rod.
7. Install the knee blocker trim panel.
8. Connect vacuum hose on the check valve in vacuum booster and vacuum fitting in intake manifold.
CAUTION: The master cylinder is used to create the seal for holding vacuum in the vacuum booster. The vacuum seal on the master cylinder MUST be replaced with a NEW seal whenever the master cylinder is removed from the vacuum booster. When removing the vacuum seal from the master cylinder do not use a sharp tool.
9. Using a soft tool such as a trim stick, remove the vacuum seal from the master cylinder mounting flange.
10. Install a NEW vacuum seal on mounting flange of the master cylinder.
11. Position master cylinder on vacuum booster, aligning push rod on vacuum booster with master cylinder piston.
12. Install the 2 nuts mounting the master cylinder to the vacuum booster. Tighten both mounting nuts to a torque of 25 Nm (225 inch lbs.).
13. Connect brake tubes to master cylinder primary and secondary ports. Tighten fittings to a torque of 17 Nm (145 inch lbs.).
14. Install the 2 structural support struts. Securely tighten the support strut attaching nuts and bolts.
15. Check the operation of the stop lamp switch and adjust if necessary.