SECTION 4B
MASTER CYLINDER
DESCRIPTION AND OPERATION
GENERAL DESCRIPTION
The master cylinder is designed for use in a diagonally split system. One front and one diagonally opposite rear brakes are served by the primary piston. The opposite front and rear brakes are served by the secondary piston.
The master cylinder incorporates the functions of the standard dual master cylinder, plus a low fluid level indicator and the proportioning valves in the non-antilock braking system. The proportioning valves limit the outlet pressure to the rear brakes after a predetermined master cylinder pressure has been reached. The brake master cylinder sensor is attached under the body of the plastic brake master cylinder reservoir.
Notice : Do not use lubricated shop air on the brake parts, as this may damage the rubber components.
Important :
- Replace all the components included in the repair kits used to service the master cylinder.
- Lubricate the rubber parts with clean brake fluid to ease assembly.
- If any hydraulic component is removed or disconnected, it may be necessary to bleed all or part of the brake system. Refer to Section 4A, Hydraulic Brakes.
- The torque values specified are for dry, unlubricated fasteners.
- Perform all service operations on a clean bench, free from all traces of mineral oil.
FLUID LEVEL SENSOR
The master cylinder is equipped with a fluid level sensor. This sensor will activate the BRAKE light if a low fluid level condition is detected. Once the fluid level is corrected, the BRAKE light will go out.
DIAGNOSTIC INFORMATION AND PROCEDURES
CHECKING THE BRAKE FLUID LEVEL
- Check the fluid level.
- If the fluid level is below MAX, refill the fluid to MAX.
CHECKING BRAKE PROPORTIONING VALVE
Use two brake pressure gauges to check the brake proportioning valves that are attached to the front under body on non-ABS braking systems. These valves limit the outlet pressure to the rear brakes after a predetermined master cylinder pressure has been reached.
When checking the brake proportioning valves, be sure that the hydraulic line pressure is measured simultaneously and diagonally on the front and the rear axle.
To measure the pressure, use the following steps:
Remove the bleeder valve and install a pressure gauge to one of the rear brake cylinders.
- Remove the bleeder valve and install a pressure gauge to one of the rear brake cylinders.
- Install another bleeder valve and install another pressure gauge to the diagonally opposite front brake.
- Build pressure by pressing firmly on the brake pedal several times. The pressure indicated on the gauge is not regulated and represents the actual brake system hydraulic pressure.
- Build pressure until the test values in the following proportioning valve test chart are achieved.
Important : If the pressure exceeds 10,000kPa (1,450 psi), the pressure reading on the rear gauge will not be accurate.
- Remove the gauges from the tested brake circuit and repeat the test on the remaining circuit.
Engine |
Reference Number for Gradient and Switching Pressure on the Valve Housing |
|
All
|
25 bar/0.25
|
REPAIR INSTRUCTIONS
ON-VEHICLE SERVICE
MASTER CYLINDER ASSEMBLY
(Left-Hand Drive Shown, Right-Hand Drive Similar)
Removal and Installation Procedure
- Remove the air intake tube from the air filter housing. (Right-Hand Drive Only)
- Remove the brake line fitting nuts from the master cylinder body.
- Disconnect the brake hoses from the master cylinder body. It is not necessary to drain the reservoir. Plug the opening to the brake lines to prevent the loss or contamination of the fluid.
Installation Notice
|
Tightening Torque
|
16 N•m (12 lb-ft)
|
- Remove the master cylinder mounting nuts.
Installation Notice
|
Tightening Torque
|
13 N•m (10 lb-ft)
|
- Remove the master cylinder assembly.
- Drain the brake fluid.
Installation Notice
- After the installation, bleed the brake system. Refer to Section 4A, Hydraulic Brakes.
- Check the brake system for leaks.
- Care must be taken to prevent the brake fluid from contacting any painted surface to prevent damage to the paint finish.
BRAKE FLUID RESERVOIR
Removal and Installation Procedure
Important : Remove the brake fluid reservoir only when it must be replaced because of damage or leaks.
- Disconnect the brake fluid level sensor connector.
- Drain the brake fluid.
- Disconnect the brake hoses from the brake fluid reservoir.
- Remove the brake fluid reservoir mounting nuts.
- Remove the brake fluid reservoir.
Installation Notice
|
Tightening Torque
|
6 N•m (4 lb-ft)
|
PROPORTIONING VALVE
Removal and Installation Procedure
- Raise and suitably support the vehicle.
- Disconnect the brake line fitting nuts from the proportioning valve.
- Remove the proportioning valve mounting nut.
- Remove the proportioning valve.
Installation Notice
|
Tightening Torque
|
Brake Line Fitting Nuts
|
16 N•m (12 lb-ft)
|
|
Tightening Torque
|
Proportioning Valve Mounting Nuts
|
7 N•m (5 lb-ft)
|
UNIT REPAIR
MASTER CYLINDER OVERHAUL
(Left-Hand Drive)
Disassembly and Assembly Procedure
- Remove the master cylinder. Refer to "Master Cylinder Assembly" in this section.
- Remove the retaining bolt and the seal from the cylinder.
Notice : When removing the retaining ring, avoid damaging the piston or the cylinder wall.
- Remove and discard the retaining ring from the cylinder body.
- Remove the primary piston assembly.
- Carefully remove the secondary piston assembly, including the spring, from the master cylinder bore.
Installation Notice
- Do not use abrasives in the master cylinder bore. Abrasives can damage the bore.
- Rubber parts and retaining ring must be discarded and replaced with new parts.
- When installing the new retaining ring, take care not to damage the cylinder bore.
- Lubricate the master cylinder bore with clean brake fluid.
- Add new brake fluid. After the installation, bleed the brake system. Refer to Section 4A, Hydraulic Brakes.
MASTER CYLINDER OVERHAUL
(Right-Hand Drive)
The master cylinder overhaul in this vehicle is not serviceable.
If the master cylinder is defective, you must replace the master cylinder assembly.
SPECIFICATIONS
FASTENER TIGHTENING SPECIFICATIONS
Application |
N•m |
Lb-Ft |
Lb-In |
Brake Line Fitting Nut (Master Cylinder) |
16 |
12 |
- |
Master Cylinder Mounting Nut |
13 |
10 |
115 |
Brake Fluid Reservoir Mounting Nut |
6 |
4 |
53 |
Brake Line Fitting Nut (Proportioning Valve) |
16 |
12 |
- |
Proportioning Valve Mounting Nut |
7 |
5 |
62 |
