Brake System Troubleshooting and Maintenance Best Practices

Preliminary Brake System Testing

Perform a preliminary test on the road or using brake testers to verify efficacy. Check for one-sided pulling and assess the hardness and elasticity of the brake pedal. Before testing, ensure tire status and pressure are correct. The wheelbase distribution is typically regulated at approximately 60% front axle and 40% rear axle.

Common Brake Fault Symptoms

• Elasticity in the pedal when braking: Presence of air in pipes, air inlet in the pump, or inappropriate brake fluid.
• Brakes lock when releasing the pedal: Saturated pump, weak or broken recoil springs, grease on the linings, poor control rod adjustment, or faulty pump cups.
• Need to depress the brake multiple times: Excessive clearance between the rod and control piston, or interplay in calipers and drums.
• No pressure achieved: Fluid loss, air in pipes, or absence of fluid in the reservoir.
• Excessive pedal travel: Play in the command piston rod, excessive gap between shoes and drum, drum dilatation due to fading, damaged brake fluid, or defective brake booster.
• Constant rubbing of shoes or pads: Excessive approach between footings, weak recoil springs, or damaged brake hoses.
• Braking imbalance: Fluid loss, caliper approximation error, stiff piston, or oil-impregnated linings.
• Overheating of the brakes: Master cylinder issues, crushed brake pipe, or handbrake seizure.
• Low braking effectiveness: Defective brake booster, worn or oily linings, or air in the circuit.
• Noises when braking: Worn pads or shoes, hardened linings, or faulty installation.
• Vibrations when braking: Warping of the disc, drum ovalization, or loose fasteners.

Brake System Service and Maintenance

Regularly inspect the wear state of hydraulic circuit components. Search for leakages along the installation and check for crushed or deformed tubing. Do not reuse brake fluid from opened containers. Ensure no impurities enter the filler cap to avoid obstructing the compensation valve. Maintain the correct fluid level and perform visual checks on patch cords. Conduct leak testing using a pressure gauge to identify external leaks or internal primary pump cup failures. Additionally, check the residual pressure valve and ensure drain paths are free of obstructions.

Brake Bleeding Procedure

1. Fill the fluid reservoir.
2. Depress the pedal several times and remove the brake booster vacuum.
3. Attach a hose to the bleeder valve leading to a container.
4. Open the bleeder and pump the pedal to remove air from the circuit until bubbles cease.
5. Once only clean fluid exits, close the bleeder and verify the fluid level.

Brake System Requirements

• Ensure proper distribution of effort between axles based on cargo.
• Ensure balanced distribution of effort between wheels on the same axle.
• Ensure the front axle begins braking before the rear axle.
• Maintain easy-setting capabilities.