Checking the brake system
Checking the effectiveness of the brake system should be carried out on a flat, dry and clean stretch of road without potholes. The check will not be truly effective if the road is wet, oily or muddy. in this case, equality of grip of all tires with the road will not be ensured. The presence of unevenness can also have a negative effect on the test, as the wheels will bounce.
The brake test must be carried out at different speeds, applying different pedal forces, however, blocking of the wheels should be avoided. Wheel lock and skidding do not indicate the effectiveness of the brake system, because. when the wheels are locked, the braking distance will be longer. The grip of the tire on the road will be stronger when the maximum braking force is applied to the wheel without locking up, and not when the tire is sliding on the road surface.
Harder braking may require more pedal effort.
Braking performance is influenced by three main external factors:
- Uneven tire grip on the road can lead to uneven braking. The pressure in all tires must be the same. Tire tread wear on the right and left sides should be approximately the same.
- Uneven vehicle load distribution can also lead to a decrease in braking efficiency, because. The wheel with the highest load requires more braking force than the other wheels.
- Violation of the wheel alignment angles, in particular the camber angles and the longitudinal inclination of the kingpin axis, causes the vehicle to pull to the side during braking.
To check for brake fluid leakage, depress and hold the brake pedal with the engine idling and the shift lever in neutral (NEUTRAL). If at the same time the pedal gradually fails, then this indicates a possible leak in the hydraulic brake system. Inspect the system to make sure there are no leaks or leaks.
Check the fluid level in the master cylinder. A slight decrease in the fluid level in the reservoir may be due to wear on the brake pad linings. A significant drop in level indicates a leak in the system. Leaks in the hydraulic drive system can be internal or external. The procedure for checking the master cylinder is shown below. Minor leaks may not be detected during this test. If the fluid level is normal, check the length of the vacuum booster pusher. If necessary, adjust the length of the pusher or replace it.
Check the operation of the master cylinder as follows:
- Check for cracks in the cylinder body casting or brake fluid leaks. A leak can be considered liquid in a volume of at least one drop. Condensation on the cylinder surface is not a leak.
- Make sure that there is no binding of the pedal drive, as well as the correct adjustment of the pusher. If both actuator and pushrod are OK, disassemble the master cylinder and check that the cylinder and piston seals are not warped or swollen. The presence of swollen gaskets indicates the use of non-standard or contaminated brake fluid. In case of fluid contamination, the master cylinder should be completely disassembled and all parts cleaned, and all o-rings should be replaced with new ones. All pipelines should also be flushed.
The use of non-standard brake fluid, the presence of mineral oil or water in it may cause the brake fluid to boil or damage the rubber seals. Swelling of the main piston plates indicates damage to the rubber seals.
If there are obvious signs of damage to the rubber elements, the hydraulic drive system should be disassembled and all parts washed with alcohol. Dry parts with compressed air prior to reassembly to prevent alcohol from entering the system. Replace all rubber elements, including hoses. In addition, when working on the brake mechanism, make sure that there is no fluid on the brake linings. If fluid is found, the pads should be replaced.
If the master cylinder piston gaskets are OK, check the system for leaks or overheating. If no leaks or overheating are found, drain the brake fluid, flush the master cylinder with it, and refill the cylinder with fluid. Then bleed the brake system to remove air from it.
Brake Hose Inspection
Checking the condition of the hoses of the hydraulic brake system must be carried out at least twice a year. Hoses should be inspected for damage from crushed stone or gravel, for cracks, abrasions or bulges in the hose outer sheath, and for leaks. Make sure the hoses are routed and fastened correctly. If the hose touches the suspension elements of the car, over time this will lead to abrasion and failure. To carry out the test, you will need a portable lamp and a mirror. If any of the above defects is found, it must be repaired or the hose replaced.
Brake Warning Light Circuit
Diagnostic instructions
The BRAKE indicator lamp illuminates brightly when the ignition switch is turned to the "ON" and either the parking brake switch or the brake fluid level sensor is closed. If the circuits of the switch and the sensor are both open, then the BRAKE indicator lamp is connected to "mass" through the generator and burns half-heartedly if the ignition switch is turned to the position "ON", and the engine is off. When the engine is turned on, the generator becomes a source of voltage. If there is voltage applied to both contacts of the lamp, it goes out.
Description of the test
The item numbers below are the step numbers in the diagnostic table.
1. This step begins the BRAKE warning light test sequence if it remains on while the engine is running.
2. This step begins the BRAKE warning lamp test sequence if it does not illuminate in all modes of operation.
Brake Warning Light Circuit
| Step | Operation | Values | Yes | No |
| 1 |
Turn on the engine and do not turn it off.
Does the BRAKE indicator light come on?
|
-
|
Go to operation 2
|
Jump to operation 10
|
| 2 |
With the engine running, release the parking brake.
Has the BRAKE indicator lamp gone out?
|
-
|
System OK
|
Go to operation 3
|
| 3 |
Check the brake fluid level.
Is the brake fluid level correct?
|
-
|
Go to operation 5
|
Go to operation 4
|
| 4 |
Does the BRAKE indicator light come on?
|
-
|
Go to operation 5
|
System OK
|
| 5 |
Disconnect the harness connector from the brake fluid level sensor on the master cylinder reservoir.
Does the BRAKE indicator light come on?
|
-
|
Jump to Operation 7
|
Go to operation 6
|
| 6 |
Replace brake fluid level sensor.
Has the renovation been completed?
|
-
|
System OK
|
-
|
| 7 |
Does the BRAKE indicator light come on?
|
-
|
Go to operation 9
|
Jump to operation 8
|
| 8 |
Replace the parking brake warning light switch.
Has the renovation been completed?
|
-
|
System OK
|
-
|
| 9 |
Repair the short in the instrument wiring harness circuit between terminal 14 of the instrument panel and ground.
Has the renovation been completed?
|
-
|
System OK
|
-
|
| 10 |
Does the BRAKE indicator light come on?
|
-
|
Go to operation 11
|
Jump to operation 13
|
| 11 |
Does the BRAKE indicator light come on?
|
-
|
Go to operation 12
|
Jump to operation 13
|
| 12 |
Replace the brake fluid level sensor in the master cylinder reservoir. The sensor can be removed and installed without draining the brake fluid from the reservoir.
Has the renovation been completed?
|
-
|
System OK
|
-
|
| 13 |
Does the BRAKE indicator light come on?
|
-
|
Go to operation 27
|
Go to operation 14
|
| 14 |
Check fuses F28 and F13.
Is fuse F12 blown?
|
-
|
Jump to operation 15
|
Jump to operation 16
|
| 15 |
Has the renovation been completed?
|
-
|
System OK
|
-
|
| 16 |
Does the measured voltage match the specified value?
|
11-14 V
|
Go to operation 18
|
Go to operation 17
|
| 17 |
Repair the voltage supply to fuses F28 and F13.
Has the renovation been completed?
|
-
|
System OK
|
-
|
| 18 |
Does the measured voltage match the specified value?
|
11-14 V
|
Jump to operation 20
|
Jump to operation 19
|
| 19 |
Repair the open circuit between tracks 1 and 2 of the dashboard and fuses F28 and F13.
Has the renovation been completed?
|
-
|
System OK
|
-
|
| 20 |
Does the measured voltage match the specified value?
|
11-14 V
|
Jump to Operation 24
|
Jump to Operation 21
|
| 21 |
Is the BRAKE indicator light correct?
|
-
|
Go to operation 22
|
Jump to operation 23
|
| 22 |
Replace instrument cluster.
Has the renovation been completed?
|
-
|
System OK
|
-
|
| 23 |
Replace the BRAKE indicator lamp.
Has the renovation been completed?
|
-
|
System OK
|
-
|
| 24 |
Does the BRAKE indicator light come on?
|
-
|
Jump to operation 25
|
Go to operation 26
|
| 25 |
Replace the BRAKE warning light switch.
Has the renovation been completed?
|
-
|
System OK
|
-
|
| 26 |
Repair the open circuit between the BRAKE warning light switch and terminal 14 of the instrument panel.
Has the renovation been completed?
|
-
|
System OK
|
-
|
| 27 |
Is the measured voltage equal to the specified value?
|
≈ 0 ohm
|
Jump to operation 28
|
Jump to operation 29
|
| 28 |
Repair open in the circuit between the brake fluid level sensor and "weight".
Has the renovation been completed?
|
-
|
System OK
|
-
|
| 29 |
Repair the open circuit between track 1 of the brake fluid level indicator and track 14 of the instrument panel.
Has the renovation been completed?
|
-
|
System OK
|
-
|