The car has two brake systems, working and parking.
Service brake system with hydraulic drive, and parking system with cable
The working brake system is dual-circuit, diagonal.
One circuit provides braking for the right front and left rear wheels.
The second circuit provides braking for the left front and right rear wheels.
If one circuit fails, the second circuit provides vehicle braking.
The hydraulic brake drive consists of a master brake cylinder with a vacuum booster, front and rear brake working cylinders and an ABS system.
All units are interconnected using hoses and tubes.
Parking brake system - with cable drive to the rear wheel brakes.
Brake mechanism of the front wheel: 1 - brake hose; 2 - bolt of the upper guide pin of the caliper; 3 - air release valve; 4 - bolt fitting of the brake hose; 5 - bolt of the lower guide pin of the caliper; 6 - brake shield; 7 - brake disc; 8 - guide pads; 9 - internal brake shoe; 10 - movable bracket
The front wheels are equipped with disc brakes, automatic adjustment of the gap between the pads and the disc, with a movable caliper
A single-piston working brake cylinder is mounted on the movable bracket.
The shoe guide is bolted to the steering knuckle.
The movable bracket is bolted to the guide pins installed in the holes of the shoe guide.
The guide pins are lubricated with grease and protected with rubber boots. A piston with a sealing ring is installed in the cavity of the moving bracket cylinder.
Due to the elasticity of this ring, an optimal clearance is maintained between the pads and the ventilated disc, the surface of which is protected by a brake shield.
When braking, the piston, under the action of fluid pressure, presses the inner pad against the disc, the reaction force moves the movable bracket on the fingers and the outer pad is also pressed against the disc, while the pressing force of the pads is the same.
When releasing the piston, due to the elasticity of the sealing ring, it is removed from the pad, resulting in a small gap between the pads and the disc.
Drum brake mechanism of the rear wheel (for clarity, the brake drum is removed): 1 - upper coupling spring; 2 - clearance adjuster lever; 3, 11 - rods of the support posts of the blocks; 4, 12 - spring plates; 5 - front brake shoe; 6 - spring of the clearance adjuster lever; 7 - lower coupling spring; 8 - brake shield; 9 - working brake cylinder; 10 - spacer bar; 13 - rear brake shoe
Drum brake mechanism of the rear wheel with automatic adjustment of the gap between the shoes and the drum.
The brake pads are actuated by a single hydraulic working cylinder with two pistons.
The optimal clearance between the drum and the shoes is maintained by a mechanical regulator mounted on the spacer bar.
Rear wheel disc brake with automatic clearance adjustment.
Rear wheel disc brake: 1 - parking brake cable; 2 - fixing bracket; 3 - bracket for fastening the parking brake cable; 4 - coupling spring; 5, 9 - brake caliper guide pins; 6 - air release valve; 7 - lever of the parking brake drive cable; 8, 13 - brake pads; 10 - brake shield; 11 - brake disc; 12 - guide pads; 14 - movable bracket
The brake pads are actuated by a single hydraulic working cylinder.
The optimal clearance between the disc and the pads is maintained according to the same principle as for the front wheel brakes.
The mechanically actuated parking brake consists of a lever mounted on the base of the body between the front seats, a front cable with an adjusting device and an equalizer, to which two cables are attached, and levers installed in the brake meters rear wheels.
The parking brake requires little maintenance. During the current repair, check the degree of wear of the teeth of the sector and the pawl.
If you find a break in the cables, replace them with new ones.
Some drivers, in an effort to reduce wear on the parking brake cables, try to use it less often.
Such "economy" leads to the opposite result: the cable, rarely moving in the shell, gradually loses mobility, it jams, as a result, the cable breaks.
Therefore, use the parking brake whenever necessary.
A vacuum booster installed between the pedal mechanism and the main brake cylinder, when braking due to vacuum in the engine intake manifold through the rod and piston of the first chamber of the main cylinder, creates an additional force proportional to the force from the pedal.
The hydraulic brake tandem master cylinder consists of two separate chambers connected to independent hydraulic circuits.
The front chamber is connected to the right front and left rear brakes, the rear chamber is connected to the left front and right rear.
Elements of the brake system located in the engine compartment: 1 - vacuum booster hose check valve; 2 - vacuum booster hose; 3 - fitting of the vacuum booster; 4 - plug of the neck of the reservoir of the main brake cylinder; 5 - reservoir of the main brake cylinder; 6 - block of wires of the brake fluid level sensor; 7 - vacuum amplifier; 8 - hose for supplying working fluid to the master cylinder of the clutch release drive; 9.13 - nuts for fastening the main brake cylinder to the vacuum booster; 10.11 - nuts for fastening pipelines of the brake system; 12 - brake master cylinder
A tank is installed on the main cylinder through rubber connecting bushings, the internal cavity of which is divided into two compartments by partitions.
Each compartment feeds one of the brake master cylinder chambers.
When you press the brake pedal, the pistons of the main brake cylinder begin to move, the working edges of the cuffs cover the compensation holes, the chambers and the reservoir are separated and the brake fluid is forced out.
Anti-lock braking system (optional).
Consists of wheel speed sensors, a switch on the brake pedal, a hydro-electronic module and a signaling device in the instrument cluster.
The anti-lock braking system is also equipped with a self-diagnosis system that detects malfunctions of system components.
The anti-lock braking system (ABS) is used to regulate the pressure in the brake mechanisms of all wheels when braking in difficult road conditions, preventing the wheels from blocking.
The ABS system provides the following benefits:
- – avoiding obstacles with a higher degree of safety, including during emergency braking;
- – reduction of the braking distance during emergency braking while maintaining roadholding and controllability of the car, including when cornering.
In the event of a system failure, diagnostics and maintenance functions are provided in case of system failures.
The hydraulic brake system is integrated into a single unit with metal pipelines and hoses.
The system is filled with a special brake fluid of at least DOT-4 class, which must be replaced periodically.
Possible brake problems and solutions
Failure cause - Remedy
Squealing, screeching when braking:
Brake pad wear limit - Replace the brake pads (preferably all on the same axle at the same time)
The introduction of foreign particles (sand) into the lining material - As a rule, it does not require intervention (the lining can be cleaned with a wire brush)
Poor quality lining material - Replace the pad (preferably all on the same axle at the same time)
Severely corroded brake disc (due to poor quality disc and/or lining material) - Grind (turn) or replace disc
The lining of the brake pad has peeled off from the base - Replace the pad (preferably all on the same axle at the same time)
Weak or broken rear brake shoe return spring - Replace spring
Increased brake pedal travel (pedal soft or falling through):
Air in the brake system, leakage of brake fluid through leaks in the hydraulic drive connections, damage to the cuffs in the main brake cylinder, pressure regulator, damage to the brake pipes and hoses - Inspect all lines, their threaded connections and cylinders, eliminate leaks.
Restore fluid level to normal in the brake reservoir and bleed the system.
If damage to the brake hoses is found (cracks, swelling or traces of brake fluid), replace the hoses.
If you suspect defects in the brake master cylinder, replace it with a known good one
The rubber cuffs of the cylinders are swollen due to the ingress of oil, gasoline, etc. into the brake fluid. - Replace cylinders, hoses, completely drain the brake fluid, flush the system with fresh fluid and pump
Brake overheating - Let the brakes cool down.
Check the thickness of the pads and brake discs.
Use only brake fluid recommended by the manufacturer in the system. Replace your brake fluid on time
The gap between the pads and the drum has been increased (the automatic gap adjustment device does not work) - Replace the wheel cylinder, bleed the system
Increased (more than 0.25 mm at the edge) runout of the brake disc - Replace the disc
One of the circuits of the working brake system does not work - Eliminate the leakage of fluid from the brake system, bleed the system
The brake pedal travel is within the normal range (the pedal is “hard”), but the car brakes badly:
Oiling brake discs, drums, linings - Clean the oiled discs and drums, replace the pads (in extreme cases, grind off with sandpaper).
It is strictly forbidden to clean the pads with solvents! Eliminate the cause of oiling (replace the axle shaft seal)
An ice or salt crust has formed on the surface of the overlays (in winter); pads are wet - At the beginning of the movement, at low speed, check the brakes. In the rain and after driving through deep puddles, dry the brakes by lightly pressing the pedal
Poor quality lining material - Replace the pads (preferably all on the same axle at the same time)
Clogged brake lines: pipes (due to dents) or hoses (due to swelling or delamination of rubber) - Replace damaged pipes and hoses
Jamming of the piston in the cylinder, pads in the caliper - Replace the cylinder, clean the contact surfaces of the pads and caliper, lubricate them with SHRUS-4 before installation
Complete wear of the brake pads (grinding of the brakes) - Replace the brake pads (preferably all on the same axle at the same time)
The lining of the brake pad has peeled off from the base - Replace the pad (preferably all on the same axle at the same time)
Incorrectly adjusted pressure regulator actuator - Adjust actuator
Faulty pressure regulator - Replace regulator
The vacuum booster is defective or the hose connecting the booster to the inlet pipeline is leaky - Check the integrity of the hose, its fit on the fittings, tightening of the clamps.
To check the amplifier, turn off the engine, press the brake pedal 5-8 times and, keeping the pedal depressed, start the engine.
With a working booster, after starting the engine, the pedal should noticeably "go" forward. Replace defective amplifier
Incomplete release of all wheels:
The rubber cuffs of the cylinders are swollen due to the ingress of oil, gasoline, etc. into the brake fluid. - Replace cylinders, hoses, completely drain the brake fluid, flush the system with fresh fluid and pump
Jamming of the piston of the main cylinder (due to corrosion, breakage of return springs, ingress of mechanical impurities into the liquid) - Replace the main cylinder, bleed the system
Brake pedal sticking: the return spring is broken or extended, the pedal bushings are worn out, the pedal bushings are not lubricated, the axle is corroded - Replace the defective spring, bushings, put fresh Litol-24 grease in them
Braking one of the wheels with the brake pedal released:
Jammed wheel cylinder piston - Replace cylinder
The rubber cuffs of the cylinders are swollen due to the ingress of oil, gasoline, etc. into the brake fluid. - Replace cylinders, hoses, completely drain the brake fluid, flush the system with fresh fluid and pump
Clogged brake lines: pipes (due to dents) or hoses (due to swelling or delamination of rubber) - Replace damaged pipes and hoses
Rear brake pad peeling off - Replace the pad (preferably all on the same axle at the same time)
Weak or broken rear brake shoe return spring - Replace spring
Deformation of the spacer bar, misalignment of the pads due to deformation of the brake plates - Straighten or replace the spacer bar, brake plates
The parking brake is pulled, the cables are wedged in the sheaths - Adjust the tension of the cables, lubricate them with engine oil, if the sheath is damaged or the wires of the cable are frayed, and also if they are severely corroded, replace them
Bad parking brake:
Incorrect drive adjustment - Adjust drive
Drive cables jammed in sheaths - Lubricate the cables with engine oil if the sheath is damaged or the wires of the cable are frayed, and also if they are severely corroded - replace them
The brake drums are oiled, frets - Clean the oily drums, replace the pads (in extreme cases, grind on emery).
It is strictly forbidden to clean the pads with solvents! Eliminate the cause of oiling (replace the axle shaft seal)
An ice or salt crust has formed on the surface of the overlays (in winter); pads are wet - At the beginning of the movement, at low speed, check the brakes.
In the rain and after driving through deep puddles, dry the brakes by lightly depressing the brake pedal
Complete wear of the brake pads (grinding of the brakes) - Replace the brake pads (preferably all on the same axle at the same time)
When the parking brake lever is released, the wheels do not brake
After a long parking of the car, the pads stuck (or froze) to the drum - While pulling the parking brake lever or cables, try to carefully (so as not to rip off the brake linings) turn the wheel.
Check the ease of movement of the cables in the shells, the pistons in the wheel cylinders, the rigidity of the return springs of the cables and the return springs of the shoes.
When parking the car, if possible, do not apply the brake, but shift into gear
Incorrect drive adjustment - Adjust drive
Drive cables jammed in sheaths - Lubricate the cables with engine oil if the sheath is damaged or the wires of the cable are frayed, and also if they are severely corroded - replace them
Moving the car away from a straight line (on a flat road):
Various tire pressure - Set normal pressure
Violation of the angles of the longitudinal inclination of the axis of rotation and / or camber of the front wheels - Adjust the angles of inclination of the axis of rotation and / or camber of the front wheels
Significant difference in tire wear - Replace worn tire
Uneven settlement or broken suspension springs - Replace both springs
Deformed parts of the suspension and / or body of the car - Straighten or replace the deformed parts and body panels
Displacement of the rear axle due to breakage of the rods or their mounting brackets - Replace the rods, weld the brackets
Wheel braking due to wheel cylinder piston seizure - Replace cylinder
Rear wheel drag due to loose or broken rear brake shoe return spring - Replace spring
Clogged brake lines: pipes (due to dents) or hoses (due to swelling or delamination of rubber) - Replace damaged pipes and hoses
Steering or skidding the car when braking:
Jammed wheel cylinder piston - Replace cylinder
Clogged brake lines: pipes (due to dents) or hoses (due to swelling or delamination of rubber) - Replace damaged pipes and hoses
Wheel jamming due to delamination of the lining from the base of the brake pad - Replace the pad (preferably all on the same axle at the same time)
Oiling brake discs, drums, linings - Clean the oiled discs and drums, replace the pads (in extreme cases, grind off with sandpaper).
It is strictly forbidden to clean the pads with solvents! Eliminate the cause of oiling (replace the axle shaft seal)
An ice or salt crust has formed on the surface of the overlays (in winter); pads are wet - At the beginning of the movement, at low speed, check the brakes.
In the rain and after driving through deep puddles, dry the brakes by lightly depressing the brake pedal
Different pressure in the tires of the left and right wheels - Set the normal pressure
Significant difference in tire wear - Replace worn tire
Distortion of the brake disc - Replace the disc (preferably in pairs)
Brake drum out-of-round - Turn or replace drum
Too little stroke of the brake pedal indicates an incorrect initial installation of the brake pedal, a violation of the adjustment of the vacuum brake booster or seizure of the working cylinder, causes increased fuel consumption and accelerated wear of the brake pads.
Too much stroke is a sign of excessive clearances in the pedal mechanism or a leak in the hydraulic drive of the brake system.
If the stroke decreases when the pedal is pressed repeatedly, i.e. it becomes "harder" - there is air in the system.
If the full pedal travel starts to increase, the system is leaking.
If the brake pedal always starts to vibrate when braking, most likely the brake discs are warped.
In such a situation, you only need to change them, and both at once.
Pedal vibration that appears and disappears periodically during hard braking accompanies the operation of the anti-lock brake system and is not a sign of a malfunction.
If the car starts to pull to the side when braking, check the slave cylinders - they may need to be replaced.
If there is a knock in the front suspension that disappears when braking, check the tightness of the caliper mounting bolts.
Evaluation of the brake system can be performed on a flat horizontal area, closed oh for traffic.
Accelerate the car without load (only the driver in the passenger compartment) to a speed of approximately 15-20 km/h.
Hardly press the brake pedal to get the maximum possible deceleration, and do not release it until the car has come to a complete stop.
If the car stopped without deviating from a straight line, and the deceleration was sufficiently intense, the braking system can be considered serviceable.
If not, check the condition of the elements and repair the system if necessary.
The following brake track length ratios must be respected:
- L lion. per. = L right. trans.
- L lion. rear = L right. rear
- L lane > L rear
If a similar test of a car equipped with ABS shows that the brake marks are clearly visible, then the anti-lock braking system is faulty.
Do not abuse this assessment, as it is associated with increased one-sided tire wear.