Test the brakes at various vehicle speeds with light and heavy pressure on the brake pedal, avoiding brake locking and tire slippage. Wheel locking during braking does not provide full information on the effectiveness of the brake compared to braking when the wheels can turn and the braking distance is shorter. This is because when a locked wheel slips, the coefficient of adhesion is lower than when it rolls.
There are three main factors that influence the braking process:
- different wheels will have different conditions of tire adhesion to the road, which will cause different braking forces. Air pressure and tire treads should be the same;
- the braking forces on the front and rear axles must be proportional to the vertical loads acting on them;
- misalignment of the wheels may cause the vehicle to pull to the side when braking.
To check for a brake fluid leak, press the brake pedal with the engine idling and the gearshift lever in neutral. If the pedal gradually sinks under constant pressure, there is a leak in the system. Visually check for a leak and the brake fluid level in the master cylinder reservoir. A slight drop in the brake fluid level is due to normal wear of the brake pads. An abnormally low level indicates a leak in the system. Both internal and external leaks are possible in a hydraulic system. If the brake fluid level is normal, check the length of the brake booster piston rod. If an improper piston rod length is found, adjust the length or replace the piston rod.
Check the brake master cylinder in the following order:
- check the master cylinder for damage or for leaks of brake fluid around the master cylinder. A drop in the brake fluid level can only indicate a leak. Wetting of the surface of the master cylinder is also an abnormal condition;
- check the pedal rod connection and the rod length. If they are normal, disassemble the brake master cylinder and check for stretching or swelling of the cylinder seals, then for wear of the rubber parts. If there are swollen seals, non-standard or contaminated brake fluid may be used. If contaminated brake fluid is found, all components should be disassembled and cleaned, and all rubber components should be replaced. All pipes should also be flushed.
Incorrect brake fluid, or mineral oil or water in the fluid, can cause the brake fluid to boil or damage the rubber components. If the main piston seals in the master cylinder are swollen, this means that the rubber components are damaged. This malfunction can be confirmed by swollen piston seals of the brake drum cylinder on the wheels. If rubber wear is confirmed, disassemble all components of the hydraulic system, wash them with alcohol. Before reassembling, dry the components with a stream of compressed air. Replace all rubber components in the system, including hoses. When the brake mechanism is operating, check for fluid in the gaskets. If fluid is found, replace the gaskets. If the condition of the piston seals of the master brake cylinder is normal, check for leaks or excessive overheating. If these conditions are not found, drain the brake fluid, fill the master brake cylinder and drain the fluid from the system again.
(Article posted on an online resource: «opelbook.ru»)
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