1999 LAND ROVER DEFENDER wheel

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LAND ROVER DEFENDER 1999 Workshop Manual 33CLUTCH
12
DESCRIPTION AND OPERATION OPERATION
Hydraulic operation
When the clutch pedal is depressed, the master cylinder piston is pushed into the master cylinder. The movement
of the piston pressu

33CLUTCH
12
DESCRIPTION AND OPERATION OPERATION
Hydraulic operation
When the clutch pedal is depressed, the master cylinder piston is pushed into the master cylinder. The movement
of the piston pressurises the fluid in the master cylinder, forcing the pressurised fluid into the hydraulic feed pipe to
the slave cylinder. The hydraulic pressure is felt at the slave cylinder piston which moves under the hydraulic force
applied, pushing the clutch release lever via the piston rod.
When the clutch pedal is released, the force applied to the release lever by the fingers of the diaphragm, moves
the release lever, which pushes the slave cylinder piston into the cylinder. The displaced hydraulic fluid is pushed
up the hydraulic feed pipe and returns to the master cylinder.
Mechanism operation
When the clutch pedal is depressed, hydraulic pressure extends the piston and rod in the slave cylinder. The
extension of the piston pushes the rod against the outer end of the release lever which pivots around the ball
spigot.
The inner end of the release lever pivots towards the engine applying pressure to the release bearing. The release
bearing slides along the release bearing sleeve and pushes on the fingers of the diaphragm. The diaphragm
pivots around the chamfered rivets in the cover. As the diaphragm is deflected, it removes pressure from the
pressure plate. The pressure plate moves away from the drive plate assisted by the three leaf springs.
The removal of force from the pressure plate on the drive plate reduces the friction between the dual mass
flywheel, drive plate and pressure plate. The drive plate slips between the flywheel and the pressure plate
preventing rotary movement being transferred from the flywheel and pressure plate to the primary driveshaft.
When the clutch pedal is released, hydraulic force is removed from the piston in the slave cylinder. This allows the
fingers of the diaphragm to push the release bearing along the release bearing sleeve. The movement of the
release bearing moves the release lever which pivots on the ball spigot, pushing the piston and rod back into the
slave cylinder.
The removal of pressure from the release bearing on the diaphragm, causes the diaphragm to pivot around the
chamfered rivets in the cover. The force applied to the pressure plate from the diaphragm overcomes the force of
the leaf springs and the pressure plate moves towards the drive plate and flywheel.
The pressure plate applies pressure to the drive plate which is pushed against the flywheel. As the clutch pedal is
progressively released, the friction between the drive plate, flywheel and pressure plate increases. The increase in
friction transfers the rotary movement of the flywheel and pressure plate to the drive plate, which in turn starts to
rotate the primary drive shaft. When the clutch pedal is released fully, the force applied by the diaphragm to the
pressure plate forces the drive plate onto the flywheel with no slippage.
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