Automobile Operation: Disassembling and Reassembling the brake master cylinder and Method of Execution

 

Disassembling and reassembling of the brake master cylinder is an operation that a mechanic does frequently, owing to the heavy work to which it is subjected and the resulting continuous wear to its components. This should be done every time that a general repair to the brakes is done, or in preventive maintenance of them, and consists of dismantling, cleaning, inspecting, changing and replacing its parts.

 

Method of Execution:

To disassemble. Brake Master Cylinder

 

1st Step - Remove the Brake Master Cylinder, thus: -

 

a) Disconnect the outlet tubing from the master cylinder.

b) Disconnect the electric cables of the "STOP" light unit.

c) Remove the securing screws from the cylinder and remove the latter from the vehicle.

Observation

Isolate the cables so as to prevent short-circuiting.

 

 

2nd Step - Clean the outside surface of the cylinder, thus: -

a) Take off the cover from the reservoir and empty it.

b) Remove the dust cover.

c) Clean the body of the cylinder.

 

3rd Step - Remove the internal parts of the cylinder, thus: -

a) Hold the cylinder in a bench vice. 

b) Remove the circlip while pushing down the piston to prevent it from jumping, because of the tension in the spring and, once the circlip has been withdrawn, release it slowly. (Fig. 1) 

c) Remove the piston, the rubber, the spring and the valve.

 

OBSERVATION

Use soft metal jaws so as to prevent damage to the body.

 

4th Step - Clean the disassembled parts thus: -

a) Clean all the parts and the interior of the body of the master cylinder with alcohol.

b) Dry all the parts with compressed air.

To Reassemble Brake Master Cylinder

1st Step - Inspect all the parts of the cylinder thus: -

a) Make sure that the surfaces of the cylinder and piston are not scratched.

b) Make sure that the charge and discharge ports of the cylinder are clean.

c) Check the play between the piston and cylinder according to the manufacturer's specifications.

OBSERVATION

Replace the rubbers every time that the master cylinder is disassembled, after they have been used

2nd Step - Replace the parts into the master cylinder, thus: -

a) Lubricate the interior of the cylinder and all its parts with the same fluid that is to be used in the system.

b) Replace the secondary rubber on the piston (fig. 3).

c) Hold the body of the master cylinder in a bench vice.

d)  Replace the parts in the order indicated (fig. 4).

OBSERVATION

To install the circlip or snap ring push the piston until the groove of its housing is uncovered.

3rd Step - Check the working of the master cylinder thus: -

a) Place the master cylinder in the vice in the same position where it works when in the vehicle.

b) Fill the master cylinder reservoir with brake fluid.

c) Activate the piston until fluid flows out of the discharge port of the master cylinder.

d) Cover the discharge port and activate the piston so as to build up the pressure within the master cylinder.

e) Make sure that the fluid does not come out of the rear part of the master cylinder.

OBSERVATION

Use plugs to seal the discharge port.

4^th Step - Replace the master cylinder„ thus:-

a) Replace the brake master cylinder into the vehicle and secure it there by means of its screws.

b) Connect the outlet tubing of the brake master cylinder.

c) Connect the electric cables of the stop light unit.

OBSERVATION

Take care not to ground the cable so as to avoid short circuiting.