Table of contents: External factors affecting the…↓ Brake fluid leaks ↓ Checking the master brake cylinder ↓ Incorrect or contaminated brake fluid ↓
The brake system is checked on a dry, clean and fairly level area with good coverage. Reliable testing of the brake system condition on wet or muddy surfaces (including dry sand) the site will be difficult due to the different grip of the tires on the surface. An uneven surface is also not suitable for testing the braking system due to strong vertical vibrations of the wheels.
The braking system should be tested under different braking intensities and at different vehicle speeds.
The vehicle's braking system is designed to prevent the wheels from locking except when the vehicle's speed is 5 km/h or less.
External factors affecting the operation of the braking system
Tires
Tires with different contact and traction with the road will brake differently. It's important to maintain consistent tire pressure. Tires on the same axle should have approximately the same tread depth.
Vehicle load
When the vehicle is unevenly loaded, those wheels that bear a larger share of the load require more braking torque than the others. Braking a fully loaded vehicle requires greater force on the brake pedal.
Wheel alignment angles
Failure to install the correct wheel alignment angles, especially camber and longitudinal tilt of the steering axis, will cause the vehicle to pull to the side when braking.
Brake fluid leaks
With the engine idling and the transmission in neutral, press and hold the brake pedal with constant force. If the brake pedal drops slowly, it may be due to brake fluid leaks.
- Inspect the entire brake system for leaks.
- Check the brake fluid level in the reservoir. A slight drop in fluid level may be due to normal wear of the brake pads. A sharp drop in the level may indicate the presence of fluid leaks. Both internal and external fluid leaks are possible in the hydraulic brake system. It should be kept in mind that even if this test passes, the system may still have small leaks. If the brake fluid level is normal, the adjustment of the service brake system and the parking brake should be checked.
Checking the master brake cylinder
The following tests do not guarantee detection of all possible faults of the unit.
- Check for cracks in the cylinder body and traces of brake fluid on the outer surface of the cylinder. Moistening of the cylinder from the outside is acceptable.
- Check for binding in the pedal drive and the length of the push rod. If no fault is found, remove and disassemble the cylinder.
- Check the condition of the cylinder and piston seals. If the seals are swollen or elongated, the brake fluid may be unsuitable or contaminated with foreign substances. In this case, it is necessary to completely disassemble the cylinder and wash all parts. Rubber parts must be replaced. The entire hydraulic drive of the brake system should also be flushed.
Incorrect or contaminated brake fluid
The use of non-recommended brands of brake fluids, as well as the ingress of mineral oil or water into the hydraulic drive leads to a decrease in the boiling point of the working fluid and failure of the rubber seals,
Swelling of the outer sealing boots on the main or wheel brake cylinders indicates failure of the internal rubber seals. If signs of swelling of rubber parts are detected, it is necessary to disassemble and completely flush the entire hydraulic drive with alcohol. Before assembly, it is necessary to dry all hydraulic drive parts with a jet of compressed air to prevent alcohol from entering the brake system. Rubber parts, including brake hoses, must be replaced. You should also check for traces of brake fluid on the brake linings. If the linings are heavily contaminated, they must be replaced. If the master cylinder seals are OK, the possible cause is overheating of the brake fluid. If there is no overheating, you should drain the brake fluid, flush the system with fresh brake fluid, fill it with new brake fluid and remove air from the hydraulic drive.