Contents: Checking the brake system ↧ Inspecting the brake hose ↧ Brake warning lamp electrical circuit ↧
Checking the brake system
The braking efficiency test should be performed on a flat, dry and clean road surface free of potholes. The test will not be truly effective if the road is wet, oily or muddy, as the equal grip of all tyres on the road will not be ensured. The presence of uneven surfaces can also have a negative effect on the test, as the wheels will bounce.
The brake system should be tested at different speeds, applying different pedal forces, but avoiding wheel locking. Wheel locking and skidding do not indicate the effectiveness of the brake system, since the braking distance will be longer with locked wheels. The tire's grip on the road will be stronger when maximum braking force is applied to the wheel without locking, and not when the tire is sliding on the road surface.
Harder braking may require more pedal force.
There are three main external factors that influence braking efficiency:
- Uneven tire grip can cause uneven braking. The pressure in all tires should be the same. The wear of the tire tread on the right and left sides should be approximately the same.
- Uneven distribution of vehicle load can also result in reduced braking efficiency, as the wheel with the highest load requires more braking force than the other wheels.
- Violation of wheel alignment angles, in particular camber angles and longitudinal tilt of the kingpin axis, causes the vehicle to pull to the side when braking.
To check for brake fluid leaks, press and hold the brake pedal with the engine idling and the gearshift lever in the NEUTRAL position. If the pedal gradually sinks, this indicates a possible leak in the brake hydraulic 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 of the brake shoe linings. A significant decrease in the level indicates leaks in the system. Leaks in the hydraulic drive system can be internal or external. The procedure for checking the master cylinder is given below. Minor leaks may not be detected during this check. If the fluid level is normal, check the length of the vacuum booster pushrod. If necessary, adjust the length of the pushrod or replace it.
Check the functionality of the master cylinder as follows:
- Check for cracks in the cylinder body casting and for leaks of brake fluid. A leak is considered to be at least one drop of fluid. Condensation on the cylinder surface is not a leak.
- Make sure the pedal drive is not sticking and that the pushrod is adjusted correctly. If both the drive and the pushrod are normal, disassemble the master cylinder and make sure the cylinder and piston seals are not deformed or swollen. Swollen seals indicate that non-standard or contaminated brake fluid is being used. If the fluid is contaminated, the master cylinder should be completely disassembled and all parts should be cleaned, and all sealing rings should be replaced with new ones. All pipelines should also be flushed.
Using non-standard brake fluid, or having mineral oil or water in it, can 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, disassemble the hydraulic drive system and wash all parts with alcohol. Before assembly, dry the parts with a stream of compressed air to prevent alcohol from entering the system. Replace all rubber elements, including hoses. In addition, when working with the brake mechanism, make sure there is no fluid on the brake pads. If fluid is found, replace the pads.
If the master cylinder piston seals 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.
Inspecting the brake hose
The condition of the hydraulic brake system hoses should be checked at least twice a year. The hoses should be checked for damage from gravel or crushed stone, cracks, abrasions on the outer casing of the hose or swelling, and for leaks. Make sure that the hoses are correctly routed and secured. If the hose touches the vehicle's suspension elements, this will eventually lead to abrasion and failure. To perform the check, you will need a portable lamp and a mirror. If any of the above defects are found, it should be repaired or the hose should be replaced.
Brake warning lamp electrical circuit
Diagnostic guidelines
The BRAKE indicator lamp glows brightly when the ignition switch is turned to the "ON" position and either the parking brake switch or the brake fluid level sensor circuit is closed. If the switch and sensor circuits are both open, the BRAKE indicator lamp is connected to ground via the alternator and glows dimly when the ignition switch is turned to the "ON" position and the engine is off. When the engine is started, the alternator becomes the source of voltage. If there is voltage applied to both terminals of the lamp, it goes out.
Description of the test
The item numbers below are the step numbers in the diagnostic chart.
1. This step begins the sequence of checking the BRAKE indicator lamp if it remains on while the engine is running.
2. This step begins the sequence of checking the BRAKE indicator lamp if it does not light in all operating modes.
Brake warning lamp electrical circuit
| Step | Operation | Values | Yes | No |
| 1 |
Turn on the engine and leave it running.
Is the BRAKE indicator light on?
|
-
|
Jump to operations 2
|
Jump to operations 10
|
| 2 |
With the engine running, release the parking brake.
Is the BRAKE indicator light out?
|
-
|
The system is normal
|
Jump to operations 3
|
| 3 |
Check the brake fluid level.
Is the brake fluid level normal?
|
-
|
Jump to operations 5
|
Jump to operations 4
|
| 4 |
Is the BRAKE indicator light on?
|
-
|
Jump to operations 5
|
The system is normal
|
| 5 |
Disconnect the wiring harness connector from the brake fluid level sensor on the master cylinder reservoir.
Is the BRAKE indicator light on?
|
-
|
Jump to operations 7
|
Jump to operations 6
|
| 6 |
Replace the brake fluid level sensor.
Is the renovation finished?
|
-
|
The system is normal
|
-
|
| 7 |
Is the BRAKE indicator light on?
|
-
|
Jump to operations 9
|
Jump to operations 8
|
| 8 |
Replace the parking brake indicator light switch.
Is the renovation finished?
|
-
|
The system is normal
|
-
|
| 9 |
Repair the short circuit in the instrument wiring harness circuit between terminal 14 of the instrument panel and ground.
Is the renovation finished?
|
-
|
The system is normal
|
-
|
| 10 |
Is the BRAKE indicator light on?
|
-
|
Jump to operations 11
|
Jump to operations 13
|
| 11 |
Is the BRAKE indicator light on?
|
-
|
Jump to operations 12
|
Jump to operations 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.
Is the renovation finished?
|
-
|
The system is normal
|
-
|
| 13 |
Is the BRAKE indicator light on?
|
-
|
Jump to operations 27
|
Jump to operations 14
|
| 14 |
Check fuses F28 and F13.
Is fuse F12 blown?
|
-
|
Jump to operations 15
|
Jump to operations 16
|
| 15 |
Is the renovation finished?
|
-
|
The system is normal
|
-
|
| 16 |
Does the measured voltage match the specified value?
|
11-14 V
|
Jump to operations 18
|
Jump to operations 17
|
| 17 |
Eliminate the fault in the voltage supply to fuses F28 and F13.
Is the renovation finished?
|
-
|
The system is normal
|
-
|
| 18 |
Does the measured voltage match the specified value?
|
11-14 V
|
Jump to operations 20
|
Jump to operations 19
|
| 19 |
Repair the open circuit between contacts 1 and 2 of the instrument panel and fuses F28 and F13.
Is the renovation finished?
|
-
|
The system is normal
|
-
|
| 20 |
Does the measured voltage match the specified value?
|
11-14 V
|
Jump to operations 24
|
Jump to operations 21
|
| 21 |
Is the BRAKE indicator light working properly?
|
-
|
Jump to operations 22
|
Jump to operations 23
|
| 22 |
Replace the instrument cluster.
Is the renovation finished?
|
-
|
The system is normal
|
-
|
| 23 |
Replace the BRAKE indicator lamp.
Is the renovation finished?
|
-
|
The system is normal
|
-
|
| 24 |
Is the BRAKE indicator light on?
|
-
|
Jump to operations 25
|
Jump to operations 26
|
| 25 |
Replace the BRAKE indicator light switch.
Is the renovation finished?
|
-
|
The system is normal
|
-
|
| 26 |
Repair the open circuit between the BRAKE indicator lamp switch and terminal 14 of the instrument panel.
Is the renovation finished?
|
-
|
The system is normal
|
-
|
| 27 |
Is the measured voltage equal to the specified value?
|
≈ 0 Ohm
|
Jump to operations 28
|
Jump to operations 29
|
| 28 |
Repair the open circuit between the brake fluid level sensor and ground.
Is the renovation finished?
|
-
|
The system is normal
|
-
|
| 29 |
Repair the open circuit between terminal 1 of the brake fluid level indicator and terminal 14 of the instrument panel.
Is the renovation finished?
|
-
|
The system is normal
|
-
|