Defender 300Tdi (1996+). Manual — part 35
CLUTCH
1
FAULT DIAGNOSIS
CLUTCH ASSEMBLY CONDITIONS
For the clutch to operate correctly it is important the
following conditions are satisfied:-
The primary shaft (15) must be free in the
crankshaft spigot bush (17).
The friction plate (2) must be able to slide easily on
the splines on the primary shaft (15), to a position
where it does not contact either the flywheel or the
pressure plate.
The friction plate must not be distorted or the
linings contaminated with oil, which may cause it to
stick or continue to run in contact with the flywheel
or pressure plate.
A number of faults can develop in the operation of the
clutch for a variety of reasons and most faults are due
to normal wear at high mileage. Problems can also
occur if the unit has been renewed by an unskilled
operator.
Recognising and diagnosing a particular clutch fault is
therefore of paramount importance in ensuring that
the problem is rectified at the first attempt.
Problems which develop in the clutch are as follows:-
Clutch spin/drag
Clutch slip
Clutch judder/fierce
CLUTCH SPIN - DRAG
Symptoms
Clutch spin is that, with engine running and clutch
pedal depressed, the gears cannot be immediately
engaged without making a grinding noise. This
indicates the clutch is not making a clean break.
However, if the clutch pedal is held depressed for
several seconds the friction plate will eventually break
free from the engine and the gear will engage silently.
Clutch spin as it becomes more severe develops into
clutch drag, making the silent engagement of a gear
impossible, regardless of how long the pedal is held
depressed.
CLUTCH SLIP
Symptoms
Clutch slip is most evident climbing a hill or when the
vehicle is moving off from stationary with a heavy
load. As the clutch is released, slip occurs between
the engine and the transmission, allowing the engine
speed to increase without a corresponding increase in
vehicle speed.
Clutch slip can develop to the stage where no power
is transmitted through the clutch as the pedal is
released.
CLUTCH JUDDER - FIERCE
Symptoms
Clutch judder or fierce engagement, like slip, is most
likely to occur when the vehicle is moving off from
stationary. As the clutch pedal is released the vehicle
will move rapidly or in a series of jerks, which cannot
be controlled even by careful operation of the clutch
by the driver.
It should be noted that a vehicle may display all the
symptoms or any combination of the symptoms
described, depending on the driving conditions vehicle
load and operating temperatures.
33
CLUTCH
2
FAULT DIAGNOSIS
FAULT/SYMPTOM CHART
Symptoms
Slip
Spin/Drag
Judder/Fierce
Fault
Item
*
*
*
Worn or oil on clutch linings
2
*
*
*
Mechanical damage
4 5 6 7 8
*
*
Distorted clutch plate
2
*
Failed or air in hydraulic system
12 13
*
*
Primary shaft tight fit in crankshaft bush
15 17
*
Clutch splines sticking
2 15
*
Weak clutch plate springs or insecure/worn
engine/gearbox mountings
6
*
Insecure/worn propeller shafts
*
Insecure/worn suspension components/rubber
bushes
The items refered to in this chart relate to the clutch components shown in J6270 and J6271.
See Description
and operation, Description
CLUTCH NOISE - MECHANICAL FAULTS
Noise from clutch or gearbox in neutral, which
disappears when clutch is depressed.
Suspect gearbox input/primary shaft bearings
See MANUAL GEARBOX, Fault diagnosis,
R380 gearbox .
Noise from clutch or gearbox in neutral, which
changes tone or becomes worse when the clutch
is depressed.
Suspect worn release bearing.
Knocking/rattling from clutch or gearbox in
neutral, which is reduced or disappears when the
clutch is depressed.
Suspect worn/weak release lever retainer or
clutch unit.
Noise from clutch or gearbox in neutral, which
disappears when clutch is depressed.
Suspect gearbox fault
See MANUAL
GEARBOX, Fault diagnosis, R380 gearbox .
HYDRAULIC FAULTS
Unable to dis-engage clutch, little or no pedal
resistance.
1. Check condition, specification and level of fluid.
2. Check pipes and cylinders for leaks.
3. Check that air vent in reservoir lid is clear.
Suspect faulty master cylinder if no fluid leaks
present
See Repair, Master cylinder .
Spongy pedal operation
1. Check condition, specification and level of fluid.
2. Check that air vent in reservoir lid is clear.
Suspect air in fluid
See Repair, Bleed
hydraulic system .
Clutch is difficult to dis-engage and/or does not
immediately re-engage when pedal is released.
1. Check condition, specification and level of fluid.
2. Check that air vent in reservoir lid is clear.
Suspect pedal pivot, master cylinder or slave
cylinder seizure
See Repair, Master cylinder .
CLUTCH
1
ADJUSTMENT
CLUTCH PEDAL AND MASTER CYLINDER
SETTING
1. Remove 6 screws and detach pedal box top
cover and gasket.
2. Slacken both locknuts on master cylinder
push-rod.
3. Check distance from lower edge of clutch pedal
to floor. Correct measurement is 140 mm (5.50
in) without floor mat.
4. Adjust pedal stop as necessary to obtain correct
setting.
5. Adjust master cylinder push rod to obtain
approximately 1,5 mm (1/16 in) free play
between push-rod and master cylinder piston.
6. Tighten push-rod locknuts.
7. Check operation of clutch pedal and ensure that
there is a minimum of 6 mm (0.25 in) of free play
before pressure is felt. If necessary, readust
master cylinder push-rod.
8. Fit pedal box gasket and top cover.
CLUTCH
1
REPAIR
CLUTCH ASSEMBLY
Service repair no - 33.10.01
Clutch pressure plate
Renew pressure plate if diaphragm spring fingers are
worn or if pressure plate shows signs of wear, cracks
or burning.
Clutch driven plate
Renew driven plate if centre hub splines are worn or if
lining is contaminated, burned or unevenly worn.
Remove
1. Remove gearbox
See MANUAL GEARBOX,
Repair, R380 Gearbox .
2. Mark position of clutch pressure plate to flywheel
for reassembly.
3. Remove pressure plate securing bolts, working
evenly and diagonally.
4. Remove clutch assembly.
5. Withdraw clutch driven plate.
Refit
NOTE: To prevent driven plate sticking,
lubricate splines using Rocol MV 3 or
Rocol MTS 1000 grease.
6. Using centralising tool LRT-12-040 to support
clutch driven plate locate pressure plate on
flywheel dowels. If fitting original pressure plate,
align assembly marks.
7. Secure pressure plate cover fixings evenly,
working in a diagonal sequence. Tighten to
34Nm (25 lbf/ft).
8. Fit gearbox to engine
See MANUAL
GEARBOX, Repair, R380 Gearbox .
BLEED HYDRAULIC SYSTEM
Service repair no - 33.15.01
Procedure
NOTE: During bleed procedure, keep fluid
reservoir topped up to avoid introducing
air to system. For hydraulic fluid
recommendations
See LUBRICANTS, FLUIDS
AND CAPACITIES, Information, Recommended
lubricants and fluids .
1. Attach suitable tubing to slave cylinder bleed
screw.
2. Place free end of tube in a glass jar containing
clutch fluid.
3. Loosen bleed screw.
4. Pump clutch pedal, pausing at end of each
stroke, until fluid from tubing is free of air.
NOTE: Keep free end of tube below
surface of fluid.
5. Hold clutch pedal down, tighten bleed screw.
6. Top up fluid reservoir.
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