Freelander System Description and Operation
BRAKES
DESCRIPTION AND OPERATION
70-9
ABS Master Cylinder
When the brake pedal is pressed, the front push rod in the brake servo assembly pushes the primary piston along the
cylinder bore. This produces pressure in the primary pressure chamber which, in conjunction with the primary spring,
overcomes the secondary spring and simultaneously moves the secondary piston along the cylinder bore. The initial
movement of the pistons, away from the piston stops, closes the primary and secondary centre valves. Further
movement of the pistons then pressurizes the fluid in the primary and secondary pressure chambers, and thus the
brake circuits. The fluid in the chambers, behind the pistons, is unaffected by movement of the pistons and can flow
unrestricted through the feed holes between the chambers and the reservoir.
When the brake pedal is released, the primary and secondary springs push the pistons back down the bore of the
cylinder. As the pistons contact the piston stops, the primary and secondary centre valves open, which allows fluid to
circulate unrestricted between the two hydraulic circuits and the reservoir, through the centre valves, the chambers
behind the pistons and the feed holes.
