Master Cylinder Replacement - Power Brake Models
1. Before removing the master cylinder, remove the brake fluid from the reservoir by sucking it out with a siphon or opening the bleeder fittings on the brake calipers and depressing the brake pedal several times. After removing the fluid, tighten the bleeder fittings.
2. Disconnect the wire connectors from the brake light switches on the master cylinder.
3. Disconnect the brake pipes from the master cylinder body. Mark the position of the tubes with tags to ensure their correct installation in the future. Plug the brake cylinder outlets and tube ends to prevent fluid loss and dirt ingress.
4. Remove two nuts (13 mm) and remove the washers securing the master cylinder to the servo, then remove the master cylinder by sliding it forward.
5. Remove the cap from the reservoir and pour out the remaining brake fluid.
6. Installation of the master cylinder is carried out in the reverse order. Install a new O-ring under the master cylinder.
7. After installing the cylinder, fill the reservoir with new brake fluid and bleed the brake system as described earlier.
Master Cylinder Replacement - Models Without Brake Servo
The master brake cylinder is mounted directly on the rear bulkhead of the engine compartment, opposite the brake pedal.
Cylinder replacement is carried out in the same way as on models with a servo amplifier. After loosening the nuts, slide the cylinder forward to remove it from the pedal pusher.
When installing the cylinder, make sure that the pedal pusher enters through the hole in the boot into the recess in the primary piston of the master cylinder.
If necessary, adjust the length of the push rod so that the free play of the brake pedal is 3 mm.
Replacement of seals
The main cylinders on models with and without servos differ only in the design of the pusher (pic. A:22).
The master cylinder may be one of the following types: "ATE" (Teves), "FAG" (Schafer) or "Bendix" (Bendix). When purchasing a repair kit, you need to know the type of master cylinder.
1. Gently pry the brake fluid reservoir off the top of the master cylinder. Remove the rubber seals from the cylinder inlets.
2. Turn away from the case of the cylinder switches of stoplights.
3. Loosen the set screw at the top of the cylinder body - the screw is located between the inlets.
4. Remove the circlip from the rod side of the cylinder, then remove the pistons.
5. Turn out from an end face of primary piston the screw of restriction of a course and remove the restrictive plug, a spring and other details. Remove seals from both pistons.
6. Clean the master cylinder and pistons with methanol or clean brake fluid. Do not use mineral-based cleaning fluids such as gasoline or kerosene. Dry the parts with a lint-free cloth or blow them with compressed air.
7. If the pistons and cylinder are in good condition, assemble the master cylinder as follows:
8. Lubricate the pistons, piston seals and cylinder with clean brake fluid.
9. Install new seals on the secondary (front) piston. Install a Belleville washer on the tapered end of the piston, then the front seal with the flat surface against the piston collar (pic. A:22). Install the two rear secondary piston seals into the grooves on the rear end of the piston with the flat sides facing each other. To install the seals, it is desirable to use the installation sleeve (pic. A:21), and if not, be very careful not to damage the seals on the sharp edges of the piston grooves.
10. Install the support ring and conical spring on the rear end of the secondary piston (not to be confused with the primary piston coil spring).
11. Install new seals on the primary (rear) piston. Install the front seal with washer on the short ledge on the front side of the piston with the flat surface towards the piston (pic. A:22). On non-servo models, install the single rear seal into the groove on the rear end of the piston with the flat side facing backwards. On power assisted models, install the two rear lip seals with washers on the long tab on the rear end of the piston with flat surfaces away from the piston. The sequence of installation of parts should be as follows: flat washer, collar, plastic washer, collar and flat washer.
12. Assemble the support ring, coil spring and stop sleeve at the front end of the primary piston, secure the parts with the travel stop screw.
13. Insert the secondary and then the primary piston assembly into the master cylinder body, while guiding the sealing edges of the cuffs with a screwdriver.
14. Press the pistons into the cylinder and install the retaining ring in the groove at the end of the cylinder.
15. Screw the set screw into the cylinder body from above while holding the pistons pressed, then release the pistons.
16. On non-servo models, install the rubber boot over the master cylinder.
17. Moisten the two rubber reservoir seals with brake fluid and press them into the cylinder inlets. Press the brake fluid reservoir into the seals.
18. Screw the brake light switches into the cylinder body.
NOTE: The brake light switch screwed into the side of the brake master cylinder usually has two wiring terminals, but vehicles with a dual hydraulic fault warning light have a three terminal switch.
19. Install the master cylinder to the vehicle as described above and bleed the brake system. Depress the brake pedal and hold it for approximately ten seconds. Inspect the brake master cylinder and make sure there are no fluid leaks.
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