Vanden Plas L6-4.0L (1990)
Brake Master Cylinder: Description and Operation
Positioning Sleeve
Positioning Sleeve
POSITIONING SLEEVE
The positioning sleeve is a safety feature which ensures that in the case of a circuit failure in the front wheel brakes there sufficient master cylinder
stroke left during ABS controlled braking.
In its inoperative position the sleeve (1) is at its stopping point. The chamber (2) left of the positioning sleeve is connected with the reservoir via the
main valve. The chamber right of the sleeve is connected direct with the reservoir.
Braking without ABS control pressure is applied to the brake pedal, the booster piston (3) moves to the left pushing the positioning sleeve to the left
against the spring tension.
Braking on surfaces with a high friction coefficient under ABS control pressure is applied from the dynamic circuit by opening the main valve. The
positioning sleeve (1) moves to the right to its stopping point and pushes back the booster piston (3) as well as the brake pedal.
At the beginning of ABS control the brake pedal has a hard pedal feel.
During braking on surfaces with a low friction coefficient the booster piston and the brake pedal moves gradually to the stopping point of the position
sleeve. Therefore, no push back movement of the pedal can be felt.
