Hydraulic booster unit — description and testing (Audi 100 C3)

1. On models equipped with power steering, a hydraulic servo motor unit is used to facilitate the operation of the brake pedal. The servo motor is located between the master cylinder and the brake pedal and is operated by hydraulic pressure from the accumulator produced by the power steering pump.

2. Generally, the hydraulic unit of the servo motor is very reliable, but if the unit is damaged, it must be replaced. The failure does not affect the brake hydraulic system in any way, except that it is necessary to apply more force to the pedal.

3. To check the unit, the engine must be stopped. Loosen the return pipe connection in the servo motor unit. It is normal for a small amount of oil to leak from the servo motor, but if oil flows continuously, the unit is faulty and must be replaced.

(This article was copied from the website: Audimanual.ru)