Contents: Increased brake pedal travel ↓ Insufficient braking efficiency ↓ Incomplete release of braking of all…↓ Braking of one of the wheels with…↓ Car skidding or pulling away when…↓ Increased pedal effort when braking ↓ Squeaking or vibration of wheel…↓
The safety of the vehicle's movement largely depends on the technical condition and performance of the brake system. Therefore, it is very important to quickly identify and eliminate any malfunctions that arise, especially on the road.
Many faults can be eliminated using the methods specified in the subsection "Brake maintenance". They can be performed by the car owner himself, given certain skills. But if the vacuum booster, pressure regulator and wheel cylinder of the rear wheel brake mechanism fail, you must contact a service station.
Increased brake pedal travel
Causes of the malfunction and ways to eliminate it:
- brake fluid leak from the wheel cylinders of the front wheel brake mechanisms. Raise the front of the car and remove the wheel. Loosen the pipe union and disconnect the flexible hose from the line. Plug the holes in the hose and tube to prevent brake fluid leakage. Remove the hose from the guide bracket of the suspension strut. Loosen the two bolts securing the shoe guide to the steering knuckle and remove the shoe guide assembly with the caliper and wheel cylinder. Disconnect hose 13 (see figure 84) from the wheel cylinder, unlock and unscrew bolts 12 securing the wheel cylinder to the guide pins. In order not to damage the protective cap, it is necessary to support the edges of the guide pins with a wrench. Remove the guide 8 of the pads together with the pins and take out the brake pads 9. Do not unscrew bolts 14 connecting the caliper and the cylinder. Remove the retaining ring 6 and protective cap 5 from the cylinder and piston. Carefully, forcing a stream of compressed air through the fluid inlet, push piston 4 out of cylinder 1. Wash all parts with warm water and a cleaning solution or isopropyl alcohol. Do not use gasoline, diesel fuel, kerosene or other mineral solvents for washing, as they cause damage to the sealing ring and protective cap. Carefully check the condition of the cylinder, piston and sealing ring 3. If they are worn, damaged or heavily corroded, replace the cylinder and piston or sealing ring;
- brake fluid leak from wheel cylinders of rear wheel brake mechanisms (oil stains or streaks on brake drums). Replace the wheel cylinders, having first carried out the operations specified in the subsection "Checking the condition and replacing the rear wheel brake pads". If there are no spare cylinders, replace the sealing rings or wheel cylinders as a whole at a service station. Wash and dry the removed brake shoes and drums. After installing all the parts in place, bleed the brake system;
- air in the brake system - see subsection "Bleeding the brake hydraulic system";
- damage to the rubber seals in the master brake cylinder. In this case, the pressure in the circuits drops and the efficiency of the brakes deteriorates. To restore the operability of the master cylinder, it is necessary to replace the seals. Disconnect the pipes from the master cylinder and the block with wires from the emergency brake fluid level sensor. Close the openings in the pipes and at the master cylinder to prevent fluid leakage and foreign inclusions from getting into them. Remove the cylinder assembly with the reservoir by unscrewing the nuts securing it to the vacuum booster. Remove the emergency brake fluid level sensor and drain the brake fluid from the reservoir and the cylinder. It is not recommended to remove the reservoir from the master cylinder unless necessary. If it occurs, you need to pull the reservoir with force until the connecting bushings come out of the master cylinder sockets. Unscrew the locking screws and sequentially remove all the parts. After making sure that all the parts are in good condition, replace the seals with new ones and assemble the master cylinder in the reverse order. When assembling, lubricate the cylinder mirror, piston and sealing ring with brake fluid. After installing the master cylinder in place and connecting the pipelines to it, bleed the system.
Insufficient braking efficiency
Causes of the malfunction and ways to eliminate it:
- the brake pads are oily. Wash and dry the pads;
- piston jamming in the wheel cylinder. Remove and disassemble the wheel cylinder, eliminate the causes of jamming, replace damaged parts or the cylinder assembly (see subsection "Main faults of the brake system and methods for eliminating them"); pump the system;
- complete wear of the brake pad linings. Replace the brake pads (see subsection "Brake maintenance");
- overheating of the brakes. Frequent and prolonged use of the brakes sharply reduces the efficiency of braking due to the heating of the brake parts. In this case, it is necessary to immediately stop the car and cool the brakes.
Incomplete release of braking of all wheels
Causes of the malfunction and ways to eliminate it:
- lack of free travel of the brake pedal (see subsection "Adjusting the brake pedal free travel");
- vacuum booster valve body jammed. Replace vacuum booster;
- swelling of rubber seals of the master cylinder. Replace seals and bleed the system;
- the master cylinder piston is jammed. Replace the master cylinder and bleed the system.
Braking of one of the wheels with the pedal released
The material is posted on the website (VAZbook)
Causes of the malfunction and ways to eliminate it:
- breakage or weakening of the tension spring of the rear wheel brake shoes. Replace the spring (see subsection "Checking the condition and replacing the rear wheel brake pads");
- piston seizing in the wheel cylinder due to corrosion or swelling of the sealing rings. Replace the wheel cylinder or damaged parts;
- violation of the position of the caliper relative to the brake disc due to loosening of the bolts securing the guide of the pads to the steering knuckle. Tighten the bolts, replace damaged parts if necessary.
Car skidding or pulling away when braking
Causes of the malfunction and ways to eliminate it:
- wheel cylinder piston jamming. Replace damaged parts or wheel cylinder assembly;
- blockage of any steel tube due to dent or clogging. Replace the tube or clean it and bleed the system;
- contamination or oiling of discs, drums and linings. Clean brake parts;
- incorrect adjustment of the pressure regulator drive. Adjust the pressure regulator drive at a service station;
- pressure regulator malfunction. Check the condition of the pressure regulator (see subsection "Brake maintenance") and, if necessary, replace it at a service station;
- violation of the front wheel alignment angles. Adjust the wheel alignment angles (see section "Pendants", subsection "Front suspension");
- uneven tire pressure. Set to normal pressure.
Increased pedal effort when braking
Causes of the malfunction and ways to eliminate it:
- vacuum booster malfunction. Replace vacuum booster;
- damage to the hose connecting the vacuum booster and the engine intake pipe or loosening of its fastening on the fittings;
- swelling of cylinder seals due to gasoline, mineral oils, etc. getting into the brake fluid. Thoroughly flush the entire system with isopropyl alcohol or brake fluid, replace the seals and fluid, and bleed the system.
Squeaking or vibration of wheel brakes
Causes of the malfunction and ways to eliminate it:
- weakening of the tension spring of the rear wheel brake shoes. Replace the spring (see subsection "Checking the condition and replacing the brake pads of the rear wheels");
- ovality of brake drums. Boring and grinding of drums, not allowing its diameter to increase over 201 mm;
- oiling of friction linings. Clean linings with a wire brush, using warm water with detergents. Eliminate causes of liquid or grease getting on brake pads;
- wear of the linings. Replace the brake pads (see subsection "Brake maintenance");
- excessive runout of the brake disc or uneven wear. Turn and grind the disc, and if the thickness is less than 10.8 mm, replace it.