Symptom: a Jetta taxi, brake failure due to the replacement of the brake master cylinder, the use of a period of time after the feeling of brake soft, poor braking effect.
    Diagnosis and maintenance methods: Jetta taxi braking system, generally without ABS system, the structure is relatively simple, there is a weak brake, poor braking effect, generally may have the following reasons:
    1. There is air in the brake system, because the air is compressible, so feel the brake soft, the effect is not good.
    2. The brake system is leaking, the system can not hold pressure, resulting in poor braking effect.
    3. The caliper's free gap is too large, so that when the brake to compensate for the gap, so that the brake hysteresis, the braking effect is poor.
    4. Brake liquid quality is poor, low boiling point, brake generated bubbles.
    5. Brake master pump internal seal bad, pressure relief. Car maintenance and maintenance network
    6. The use of brake fluid and the original brake fluid is not the same brand, the same model, the two had a chemical reaction, resulting in corrosive substances, corrosion of the brake cylinder and the pump at the pump, leading to the total Pump or sub-pump seal bad, resulting in pressure relief.
    On the case of the car, the first should check whether the brake fluid used in line with the original requirements of the same brand, the same model of the product. If not, according to the requirements of the manufacturers to replace all the brake system involving brake fluid parts, and then add the brake fluid to meet the requirements, otherwise it may lead to sudden braking system failure, there are serious security risks. If there is no problem with the brake fluid, check the brake system for leaks and thoroughly exhaust the brake system. Exhaust can not be ruled out after the failure, it is likely that the new brake for the total quality of the cylinder, the internal pressure relief. Proposed replacement of the original parts of the brake system spare parts.