Discovery 2. Manual — part 531

CLUTCH - TD5

DESCRIPTION AND OPERATION

33-1-9

The pressure plate assembly comprises a pressure plate, cover and diaphragm and is mounted on and rotates with
the dual mass flywheel.

The pressure plate is forged from cast iron and machined to provide a smooth surface for the drive plate to engage
on. Three lugs on the outer diameter of the pressure plate connect it via three leaf spring to the cover. The leaf springs
have three tempered steel leaves which assist in pulling the pressure plate away from the drive plate when the clutch
pedal is depressed.

The cover is made from pressed steel and houses all pressure plate components. Shouldered rivets support the
diaphragm inside the cover. The rivets heads are chamfered to allow the diaphragm to pivot when pressure is applied
to it by the release bearing. Three holes in the cover locate on the dowels on the flywheel and six further holes provide
for the attachment of the cover to the flywheel with six nuts. Larger holes in the cover provide ventilation for the drive
plate and pressure plate and flywheel contact surfaces.

The diaphragm comprises a cast ring with eighteen fingers. The diaphragm is attached to the cover with nine
shouldered rivets. The inner head of each rivet is chamfered to allow the diaphragm to pivot when the clutch is
depressed or released. When pressure is applied to the fingers of the diaphragm by the release bearing, the
diaphragm pivots on the rivets and moves away from the pressure plate, releasing the force applied to the pressure
plate and allowing the drive plate to slip between the pressure plate and the flywheel.

Drive plate

1 Friction material
2 Inner plate
3 Hub
4 Spring steel plate

The drive plate is of the rigid centre type and is sandwiched between the flywheel and the pressure plate. The drive
plate has a splined hub which engages with the splines on the primary drive shaft from the gearbox. The hub is
attached to an inner plate which is pressed onto the hub. A spring steel plate is riveted to the inner plate with eight
rivets and provides the attachment surface for the drive plate friction material. The spring steel plate allows some axial
compliance and contributes to smooth clutch operation. The friction material comprises two 267 mm (10.5 in.) discs
which are secured with rivets to each side of the spring steel plate. The rivets are installed through recessed holes in
the disc and emerge in recessed holes in the opposite disc.

CLUTCH - TD5

33-1-10 DESCRIPTION AND OPERATION

Operation

Hydraulic operation
Refer to illustration.

+

CLUTCH - Td5, DESCRIPTION AND 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.

CLUTCH - TD5

ADJUSTMENTS 33-1-11

ADJUSTMENTS

Clutch hydraulic system - bleed

$% 33.15.01

CAUTION: Ensure the fluid in the reservoir is
maintained between the minimum and maximum
levels throughout the bleed procedure using new
brake fluid.

CAUTION: Brake fluid will damage paint finished
surfaces. If spilled, immediately remove fluid and
clean area with water.

Bleeding

1. Top up reservoir.
2. Raise the front of the vehicle.

WARNING: Do not work on or under a
vehicle supported only by a jack. Always
support the vehicle on safety stands.

3. Connect tube to bleed screw on clutch slave

cylinder and submerge free end in a clear
container containing brake fluid.

4. Loosen bleed screw, then apply steady

pressure to the clutch pedal, depressing it
through its full stroke. Allow the pedal to return
unassisted.

5. Repeat the procedure until a flow of clean, air-

free fluid is purged into the container.

6. Hold the pedal to the floor and tighten the

clutch bleed screw to 9 Nm (7 lbf.ft).

7. Check and top up reservoir.

CAUTION: Never re-use fluid that has been
bled from the system.

8. Remove stands and lower the vehicle.

CLUTCH - TD5

33-1-12 ADJUSTMENTS