MASTER CYLINDER INSPECTION
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Warning
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• Use of any brake fluid other than the specified brake fluid will cause permanent damage to brake components and will render the brakes inoperative. Failure to follow these instructions may result in personal injury.
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Note
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• Inspect the fluid level in the master cylinder before performing the inspection procedures. If the brake fluid level is not at the MAX line, add specified brake fluid.
Normal Condition
1. The following conditions are considered normal and are not indications that the master cylinder is in need of repair or replacement.
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• During normal operation of the master cylinder, the brake fluid level in the reserve tank will fall during brake application and rise during release. The net brake fluid level will remain unchanged after brake application and release.
• A trace of brake fluid may exist on the power brake unit installation part of the master cylinder. This is the result of the normal internal lubricating action of the master cylinder.
• Brake fluid level will decrease as the brake shoes and disc pad wear.
Abnormal Condition
1. Changes in brake pedal feel and travel are indications that a brake system malfunction exists. Refer to the Symptom Chart for abnormal condition diagnosis. (See BRAKE SYSTEM INSPECTION/VERIFICATION.)
Bypass Condition Verification
1. Inspect the brake system for leakage or insufficient brake fluid. Repair if necessary.
2. Observe the brake fluid level in the reserve tank as the brake pedal is slowly pressed and quickly released. If the brake fluid level rises when the brake pedal is pressed and drops when the brake pedal is released, but the net brake fluid level remains unchanged, there is a leakage inside the brake master cylinder. Repair or replace the master cylinder. (See MASTER CYLINDER REMOVAL/INSTALLATION.) (See MASTER CYLINDER DISASSEMBLY/ASSEMBLY.)
Non-Pressure External Leakage
1. A low brake fluid level in the reserve tank may be caused by the following non-pressure external leakage.
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• An external leakage may exist at the cap due to incorrect position of the cap, cap gasket, or cap gasket deterioration.
Compensator Port Inspection
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Note
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• The purpose of the compensator ports in the master cylinder is to:
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― Supply additional brake fluid needed by the brake system due to brake shoe and disc pad wear.
― Allow the brake fluid to return to the master cylinder from the brake line and allow brake fluid to enter the reserve tank. The returning brake fluid will create a slight turbulence in the reserve tank. This is a normal condition and indicates that the compensator ports are not clogged.
1. Clogged compensator ports may cause the brakes to hang up or not fully release. If clogged compensator ports are suspected, perform the following procedures:
- (1) Lift and support the vehicle.
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- (2) With the brakes released, attempt to rotate each wheel. If an excessive amount of brake drag exists, continue with the test. If an excessive amount of brake drag exists at only one wheel, it indicates a possible seized front disc brake caliper, rear wheel cylinder, or parking brake component. Repair or replace with new components as necessary.
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- (3) Verify the brake switch adjustment. And inspect the brake pedal play to verify that the brake pedal operates normally.
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- (4) Loosen the nuts attaching the master cylinder and pull the brake master cylinder away from the power brake booster.
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- (5) Repeat Steps 1 and 2. If the brake drag disappears, the power brake unit is sticking and must be replaced with a new one. (See POWER BRAKE UNIT REMOVAL/INSTALLATION.)
- If the brake drag continues, the master cylinder is sticking and must be replaced with a new one. (See MASTER CYLINDER REMOVAL/INSTALLATION.)