Analysis of Common Faults of Level Brake

The hydraulic brake device transmits the braking force by converting the pedal force into hydraulic energy. Its transmission mechanism is simple, but the braking torque generated by the brake is linearly related to the pedal force. If the adhesion of the tire to the road surface is sufficient, the car The braking force received is linear with the pedal effort. This property is called the brake pedal feeling (commonly known as the foot feeling), so the driver can directly feel whether the various conditions of the automobile brake device are normal, so as to diagnose quickly. Common faults in hydraulic brake systems are: Brake failure, such as braking.

First, the brake is not working. 1. Phenomenon: When the car is moving, the brake pedal will be stepped on quickly. The car cannot slow down and stop immediately. Its braking deceleration is small and the braking distance is too long.

2, reasons:

(1) The free travel of the pedal is too large.

(2) Brake fluid in the master cylinder is insufficient, or the compensation hole is blocked, the main pump bowl, and the apron are aged, swollen, deformed or overturned.

(3) The brake master cylinder's piston and cylinder wear too much and loose and leak oil. The return valve is badly sealed and the outlet valve spring is broken.

(4) Brake cylinders have aging, swelling, and stuck pistons. The pistons and cylinders of the cylinders are excessively worn and loose.

(5) The brake shoe wears badly, the brake gap is too large or the clearance is reversed.

(6) The brake drum is out of round, and there is too little groove or wear, there is oil on the surface of the brake shoe, the erosion hardens, and the rivet is exposed.

(7) The air is infiltrated into the hydraulic brake system, or the temperature of the brake system is too high, and the brake fluid in the pipeline is vaporized to form an air resistance.

(8) Tubing concavity, loose joint leakage, brake hose aging, rupture or blockage.

3, diagnosis and elimination When the car's hydraulic brake system fails to brake, can be used "three-foot brake" (light pedal, fast pedaling and even riding) with "feeling" method to quickly diagnose. The specific exclusion steps are as follows:

1, the first foot brake: light pedal. That is, use the toe or forefoot to gently step on the brake pedal. (1) If the pedal is felt to have brake resistance when it is 2/3 of the full stroke, the free travel of the pedal is too large and should be adjusted. (2) When using the forefoot gently step on the brake pedal. a) If the pedal feels harder than before even when the brake pedal is depressed, even if the pedal is not moving, it means that the brake master cylinder and the sub-pump bowl have swollen and deformed, resulting in seizure or sedimentation obstruction due to excessive use of the brake fluid. The pipeline. The brake fluid and brake cup should be replaced and the brake lines cleaned. b) If you feel soft and flexible when you step on the brake pedal, it means that there is air or brake fluid heated and vaporized in the hydraulic brake pipe. The pipe joints should be tightened and deflated according to the requirements of different models. c) If the pedal is released after the brake pedal is depressed, the pedal cannot be returned to the original position, indicating that the return valve of the master cylinder or the oil return hole is also blocked. If at this time there is always a "bashing" or "bashing" sound, it means that the brake master cylinder has been knocked over. The master return valve or oil return hole should be unblocked, and the master cylinder should be reassembled or replaced.

2, the second foot brake: fast step. Use the sole of your foot to quickly step on the brake pedal. (1) If the brake system with "quick pedal" brake pedal is activated in the hydraulic brake system equipped with a quick-locking joint, and the brake is invalid when the brake pedal is depressed, it indicates that the quick self-locking joint is installed or the joint is reversed. At the two springs due to improper adjustment. In this way, when the brake pedal is "rapidly depressed", the joint ball part generates a self-locking phenomenon and the brake fluid cannot pass through. In this case, it should be re-assembled, and the pressure of the oil end compression spring will be properly adjusted. (2) If the pedal feels a small free stroke and the brake is effective during the “quick ride”, when the brake pedal is slowly depressed, the free stroke is felt to be large and the brake is invalid, which means the brake master cylinder Aging, wear too much. Keep the pressure on the brake pedal unchanged. If you feel the pedal continue to move downwards, there is leakage in the brake pipe. First, conduct an external inspection of the brake pipe to see if there is any breakage, if there is any looseness at the pipe joint, and then check whether there is brake fluid leakage at the main pump push rod boot and at the wheel brake cylinder. If no brake fluid leaks out, It indicates that the main pump or the sub-pump is aging or broken, and should be replaced.

3, the third foot brake: even pedaling, that is, stepping on the brake pedal several times. (1) If the brake pedal is pressed several times in succession, the pedal is always in the end and there is no reaction force, then the fault is caused by the lack of brake fluid in the main pump reservoir, the plugging of the inlet hole and the cover vent hole, or the mechanical connection. The mechanism falls off; or the brake cup breaks or is overturned. At this point, the brake fluid should be added to the reservoir to clear the vent hole and replace the brake cup. (2) If the brake pedal is pressed several times in succession and the pedal can be raised and the braking performance is improved, check the pedal free stroke and wheel brake clearance.

Second, the brake bite 1, the phenomenon: the car is running, using one or several brakes, the car started and accelerated difficult, the car after a certain mileage, the brake drum fever.

2, reasons:

(1) The brake pedal has no free stroke.

(2) The clearance between the brake drum and brake shoe friction plate is too small, and the brake shoe return spring breaks or fatigue over blows.

(3) The brake fluid is too dirty or the precision is too large, making it difficult to return oil.

(4) The bypass hole of the main pump bypasses the oil return hole; the main pump or the sub-pump cup or apron ages, deforms, and swells.

(5) The main pump piston return spring is too soft or broken or the piston is stuck.

3, fault diagnosis and exclusion: first according to the phenomenon of failure to determine whether the whole car bite or individual bite, and then for further diagnosis.

(1) If the brake on the whole vehicle has a bite: 1) Check if the brake pedal has free stroke. 2) Open the lid of the reservoir and use the "step-by-step"

Brake pedal method, observe the oil return situation. If the return oil is slow or does not return to oil, check that the brake fluid is too dirty or excessively viscous. If the brake fluid is pure, then step on the brake once and then relax the brake pedal and loosen any one of the pump bleeder bolts. The brake fluid will be ejected and the brake will be released.

(2) If individual wheels bite: 1) First, brake the bite of the wheel, loosen the sub-pump exhaust bolt, and if the brake fluid snaps out after the brake fluid snaps out, check if the brake oil pipe is blocked. 2) After the liquid is discharged, if the brake shoe still cannot move back, check if the brake clearance is too small. 3) If the above checks are all normal, then disassemble and inspect the pistons, cups and other factors that cause the brake shoes to return poorly.

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