lock LAND ROVER DISCOVERY 1999 Workshop Manual

FRONT SUSPENSION
DESCRIPTION AND OPERATION 60-21
Engine speed signal
Reverse gear signal
Ignition ON signal
Pressure control valve failure
Directional control valves
Failure Effect
Open circuit No ACE control - 'Locked bars' condition
Short circuit - Ground No ACE control - 'Locked bars' condition
Short circuit - VBatt No ACE control - 'Locked bars' condition
Failure Effect
Open circuit No reverse signal to ECU. ACE active in reverse,
may give abnormal handling when reversing
Short circuit - Ground No reverse signal to ECU. ACE active in reverse,
may give abnormal handling when reversing
Short circuit - VBatt Permanent reverse signal to ECU. Permanent
'Locked bars' condition
Failure Effect
Open circuit ECU does not receive ignition ON signal. No ARC
control, 'Locked bars' condition
Short circuit - Ground ECU does not receive ignition ON signal. No ARC
control, 'Locked bars' condition
Short circuit - VBatt Permanent ignition ON signal to ECU. Possibility of
flat battery
Failure Effect
Open circuit No ACE control
Short circuit - Ground No ACE control
Short circuit - VBatt No ACE control
Valve stuck open No ACE control
Valve stuck closed Maximum system pressure - no proportional control.
Pressure relief valve operating at 185 bar (2683
lbf.in
2)
Failure Effect
DCV 1 DCV 2
Valve open or stuck open Valve open or stuck open No ACE control - Anti-roll bars floppy
Valve closed or stuck
closedValve closed stuck
closedNo ACE control - 'Locked bars' condition (default)
Valve open or stuck open Valve closed or stuck
closedVehicle leans to left when pressure is applied to
actuators
Valve closed or stuck
closedValve open or stuck open Vehicle leans to right when pressure is applied to
actuators

FRONT SUSPENSION
60-22 DESCRIPTION AND OPERATION
Operation
Hydraulic circuit diagram
1Pressure transducer
2Directional control valve 2
3Front torsion bar assembly
4Actuator
5Actuator
6Rear torsion bar assembly
7Directional control valve 18Valve block
9Pressure control valve
10Reservoir
11Filter
12High pressure filter
13Hydraulic pump
14Attenuator hose
Vehicle not moving
When the engine is running and the vehicle is not moving, both DCV's are closed, locking fluid in each side of the
actuator pistons. The hydraulic pump draws fluid from the reservoir and passes it at very low pressure to the valve
block. Because both DCV's are closed, after the fluid passes through the high pressure filter, it is directed through the
pressure control valve to the reservoir. The pressure control valve is open fully to allow the full flow to pass to the
reservoir. The DCV's will remain closed until the ECU detects a need to operate.

FRONT SUSPENSION
DESCRIPTION AND OPERATION 60-23
Vehicle moving and turning left
When the vehicle is turning left, the accelerometers detect the cornering forces applied and transmit signals to the
ECU. The ECU determines that an opposing force must be applied to the torsion bars to counter the cornering forces.
The ECU supplies a current to the solenoid of the DCV2. Simultaneously, a current is sent from the ECU to the
pressure control valve which operates to restrict the flow of fluid returning to the reservoir.
The restriction causes the hydraulic pressure in the system to rise and the pressure is sensed by the pressure
transducer which sends a signal to the ECU. The ECU determines from the inputs it receives what pressure is required
and adjusts the pressure control valve accordingly.
The pressure in the system is applied to the annulus of each actuator, applying an opposing force to the torsion bar
and minimising the cornering effect on the vehicle and maintaining the vehicle attitude. The fluid displaced from the
full area of the actuator is returned to the reservoir via the valve block.
As the cornering force is removed when the vehicle straightens up, the ECU opens the pressure control valve to
reduce the pressure in the system. The fluid bleeds from the actuator back into the system as the cornering force is
reduced, removing the force from the torsion bar. When the vehicle is moving in a straight line DCV 2 closes.
Vehicle moving and turning right
When the vehicle is turning right, the accelerometers detect the cornering forces applied and transmit signals to the
ECU. The ECU determines that an opposing force must be applied to the torsion bars to counter the cornering forces.
The ECU supplies a current to the solenoid of the DCV1. Simultaneously, a current is sent from the ECU to the
pressure control valve which operates to restrict the flow of fluid through the by-pass gallery.
The restriction causes the hydraulic pressure in the system to rise and the pressure is sensed by the pressure
transducer which sends a signal corresponding to the pressure to the ECU. The ECU determines from the inputs it
receives what pressure is required and adjusts the pressure control valve accordingly.
The pressure in the system is applied to the full area of each actuator, applying an opposing force to the torsion bar
and minimising the cornering effect on the vehicle and maintaining the vehicle attitude. The fluid displaced from the
annulus of the actuator is returned to the reservoir via the valve block.
As the cornering force is removed when the vehicle straightens up, the ECU opens the pressure control valve to
reduce the pressure in the system. The fluid bleeds from the actuator back into the system as the cornering force is
reduced, removing the force from the torsion bar. When the vehicle is moving in a straight line the DCV 1 closes.
Vehicle moving in a straight line
The ECU is constantly monitoring the signals received from the accelerometers and operates the DCV's and pressure
control valve to maintain the vehicle attitude when the vehicle is moving.
Off-road driving
Off-road detection is achieved by the ECU by monitoring the signals from the upper and lower accelerometers for
varying degrees of body movement. Off-road driving generates differing signals to the accelerometers which in turn
produce differing outputs due to their vertical separation and the location of the roll centre of the vehicle. The two
signals are passed through a filter to remove any offset caused by the vehicle leaning or the terrain. The ECU then
uses this signal to calculate the percentage of road roughness.
Below 25 mph (40 km/h) the percentage of road roughness calculated is used by the ECU to limit the operation of the
ACE system. The system is completely inoperative at speeds below 2 mph (3 km/h). At speeds above 25 mph (40
km/h) the system disables the percentage road roughness signal and full ACE system assistance is restored.
Side slope detection
The ECU uses side slope detection when the upper and lower accelerometers detect an average acceleration of more
than ± 0.2 g and a road speed of less than 25 mph (40 km/h).
When side slope is detected both DCV's close to provide a 'locked bars' condition. This condition increases stability
and gives a consistent vehicle response. As the road speed increases up to 25 mph (40 km/h), the level of average
lateral acceleration must also increase and be maintained for the system to recognise that the vehicle is on a side
slope. If the side slope angle is steep and the road speed is low, the ECU will detect the side slope in a short time.

FRONT SUSPENSION
60-42 REPAIRS
Refit
1.Clean mating faces of pulley and ACE pump.
2.Position pulley to ACE pump and fit bolts.
Restrain pulley and tighten bolts to 25 Nm (18
lbf.ft).
3.Clean mating faces of ACE pump and
mounting.
4.Connect suction hose to ACE pump and secure
with clip.
5.Ensure there is sufficient fluid in ACE/PAS
reservoir to prime ACE pump.
6.Position ACE pump below level of ACE/PAS
reservoir, with suction hose uppermost, and
allow fluid from ACE/PAS reservoir to
completely fill ACE pump.
7.Position ACE pump to mounting, fit bolts and
tighten to 25 Nm (18 lbf.ft).
8.Rotate ACE pump clockwise (viewed from
pulley end) until a steady flow of fluid runs from
outlet port.
9.Connect pressure pipe to ACE pump with banjo
bolt and new sealing washers. Tighten banjo
bolt to 28 Nm (21 lbf.ft).
10.Position air intake hose and secure clips.
11.Fit auxiliary drive belt.

+ CHARGING AND STARTING,
REPAIRS, Belt - auxiliary drive.
12.Renew ACE high pressure filter.

+ FRONT SUSPENSION, REPAIRS,
Filter - high pressure - ACE.
Pump - ACE - diesel
$% 60.60.10
CAUTION: The ACE hydraulic system is
extremely sensitive to the ingress of dirt or
debris. The smallest amount could render the
system unserviceable. It is imperative that the
following precautions are taken.
lACE components are thoroughly cleaned
externally before work commences;
lall opened pipe and module ports are
capped immediately;
lall fluid is stored in and administered
through clean containers.
Remove
1.Remove auxiliary drive belt.

+ CHARGING AND STARTING,
REPAIRS, Belt - auxiliary drive.
2.Disconnect multiplugs from mass air flow
sensor and ambient air pressure sensor.
3.Release clips and disconnect mass air flow
sensor from air cleaner.
4.Loosen hose clip, disconnect inlet air hose
from turbo charger and move hose aside.

FRONT SUSPENSION
60-44 REPAIRS
Refit
1.Clean mating faces of pulley and ACE pump.
2.Position pulley to ACE pump and fit bolts.
Restrain pulley and tighten bolts to 25 Nm (18
lbf.ft).
3.Clean mating faces of ACE pump and
mounting.
4.Connect suction hose to ACE pump and secure
with clip.
5.Ensure there is sufficient fluid in ACE/PAS
reservoir to prime ACE pump.
6.Position ACE pump below level of ACE/PAS
reservoir, with suction hose uppermost, and
allow fluid from ACE/PAS reservoir to
completely fill ACE pump.
7.Position ACE pump to mounting, fit bolts and
tighten to 25 Nm (18 lbf.ft).
8.Rotate ACE pump clockwise (viewed from
pulley end) until a steady flow of fluid runs from
outlet port.
9.Connect pressure pipe to ACE pump with banjo
bolt and new sealing washers. Tighten banjo
bolt to 28 Nm (21 lbf.ft).
10.Connect hose to intercooler and secure with
clip.
11.Fit ACE/PAS reservoir into mounting bracket.
12.Connect air hose to turbo charger and secure
with clip.
13.Fit mass air flow sensor to air filter and secure
with clips.
14.Connect multiplugs to mass air flow sensor and
ambient air pressure sensor.
15.Fit auxiliary drive belt.

+ CHARGING AND STARTING,
REPAIRS, Belt - auxiliary drive.
16.Renew ACE high pressure filter.

+ FRONT SUSPENSION, REPAIRS,
Filter - high pressure - ACE.
Valve block - ACE
$% 60.60.20
CAUTION: The ACE hydraulic system is
extremely sensitive to the ingress of dirt or
debris. The smallest amount could render the
system unserviceable. It is imperative that the
following precautions are taken.
lACE components are thoroughly cleaned
externally before work commences;
lall opened pipe and module ports are
capped immediately;
lall fluid is stored in and administered
through clean containers.
Remove
1.Raise vehicle on a ramp.
2.Disconnect 4 multiplugs from valve block.
3.Position container underneath valve block to
collect fluid spillage.

FRONT SUSPENSION
REPAIRS 60-45
4.Remove 2 bolts securing 2 rear pipe clips to
chassis. 5.Remove 2 nuts securing rear pipe clamping
plate. Release clamping plate and pipes from
valve block.
CAUTION: Always fit plugs to open
connections to prevent contamination.
NOTE: Keep pipes assembled to clamping
plate to maintain correct pipe positions for
refitting.
6.Remove 2 nuts securing front pipe clamping
plate.

FRONT SUSPENSION
60-46 REPAIRS
7.Remove 3 bolts securing valve block to
chassis.
8.Release front pipes and clamping plate from
valve block and remove valve block.
CAUTION: Always fit plugs to open
connections to prevent contamination.
NOTE: Keep pipes assembled to clamping
plate to maintain correct pipe positions for
refitting.
9.Remove 6 bushes from valve block. Refit
1.Fit 6 bushes to valve block.
2.Ensure valve block and pipe connections are
clean.
3.It is important that the pipe ends are in good
condition to achieve a seal.
4.Position valve block and connect front pipes
and clamping plate. To avoid damage to
seals, keep pipes square to valve block. Fit
and tighten bolts securing valve block to
chassis to 18 Nm (13 lbf.ft).
CAUTION: Ensure pipes are installed in
their correct ports or serious system
damage will occur.
5.Fit and tighten nuts securing front clamping
plate to valve block to 21 Nm (15 lbf.ft).
6.Fit bolt securing front pipe clip to chassis and
tighten to 6 Nm (4.4 lbf.ft).
7.Connect rear pipes and clamping plate to valve
block. To avoid damage to seals, keep pipes
square to valve block. Fit and tighten nuts
securing clamping plate to valve block to 21 Nm
(15 lbf.ft).
CAUTION: Ensure pipes are installed in
their correct ports or serious system
damage will occur.
8.Fit bolts securing rear pipe clips to chassis and
tighten to 6 Nm (4.4 lbf.ft) .
9.Connect 4 multiplugs to valve block.
10.If the same valve block has been refitted, renew
ACE high pressure filter.

+ FRONT SUSPENSION, REPAIRS,
Filter - high pressure - ACE.
11.Bleed ACE hydraulic system.

+ FRONT SUSPENSION,
ADJUSTMENTS, ACE hydraulic system
bleeding.
12.Lower vehicle.

FRONT SUSPENSION
REPAIRS 60-47
Filter - high pressure - ACE
$% 60.60.21
CAUTION: The ACE hydraulic system is
extremely sensitive to the ingress of dirt or
debris. The smallest amount could render the
system unserviceable. It is imperative that the
following precautions are taken.
lACE components are thoroughly cleaned
externally before work commences;
lall opened pipe and module ports are
capped immediately;
lall fluid is stored in and administered
through clean containers.
Remove
1.Raise vehicle on a ramp.
2.Position container to collect fluid spillage.
3.Remove filter cap and discard 'O' ring.
4.Fit M6 bolt into base of filter and pull on bolt to
remove filter from valve block. Do not turn
filter in valve block.
CAUTION: Always fit plugs to open
connections to prevent contamination.Refit
1.Ensure new filter has 'O' ring fitted, then fit filter
to valve block.
2.Fit new 'O' ring to filter cap. Fit cap and tighten
to 35 Nm (26 lbf.ft).
3.Lower vehicle.
4.Check fluid level in ACE/PAS reservoir.

+ FRONT SUSPENSION,
ADJUSTMENTS, Fluid level check - ACE
system.
5.Start and run engine for 2 minutes, then re-
check fluid level in ACE/PAS reservoir.

+ FRONT SUSPENSION,
ADJUSTMENTS, Fluid level check - ACE
system.

FRONT SUSPENSION
60-48 REPAIRS
Pressure transducer - ACE
$% 60.60.22
CAUTION: The ACE hydraulic system is
extremely sensitive to the ingress of dirt or
debris. The smallest amount could render the
system unserviceable. It is imperative that the
following precautions are taken.
lACE components are thoroughly cleaned
externally before work commences;
lall opened pipe and module ports are
capped immediately;
lall fluid is stored in and administered
through clean containers.
Remove
1.Raise vehicle on a ramp.
2.Disconnect multiplug from transducer.
3.Position container to collect fluid spillage.
4.Remove pressure transducer and discard 'O'
ring.
CAUTION: Always fit plugs to open
connections to prevent contamination.Refit
1.Ensure pressure transducer and port in valve
block is clean.
2.Fit new 'O' ring to pressure transducer. Fit and
tighten pressure transducer to 20 Nm (15
lbf.ft).
3.Connect multiplug to pressure transducer.
4.Renew ACE high pressure filter.

+ FRONT SUSPENSION, REPAIRS,
Filter - high pressure - ACE.
5.Lower vehicle.

FRONT SUSPENSION
REPAIRS 60-49
Solenoid - pressure control valve - ACE
$% 60.60.23
Remove
1.Raise vehicle on a ramp.
2.Disconnect multiplug from solenoid.
3.Remove cap securing solenoid to pressure
control valve and discard 'O' ring.
4.Remove solenoid from pressure control valve
and discard 'O' ring from base of valve.
Refit
1.Ensure solenoid and pressure control valve are
clean.
2.Fit new 'O' ring to base of pressure control
valve.
3.Fit solenoid to pressure control valve, with
arrow on solenoid pointing away from valve
block and connector in correct position.
4.Fit new 'O' ring to solenoid securing cap. Fit cap
and tighten to 11 Nm (8 lbf.ft).
5.Connect multiplug to solenoid.
6.Lower vehicle.
Solenoid - directional control valve - ACE
$% 60.60.24
Remove
1.Raise vehicle on a ramp.
2.Disconnect multiplug from solenoid.
3.Loosen cap securing solenoid to directional
control valve.
4.Remove 3 bolts securing valve block to
chassis, lower block sufficiently only to remove
solenoid.
5.Remove cap securing solenoid to directional
control valve and discard 'O' ring.
6.Remove solenoid from directional control valve
and discard 'O' ring from base of valve.
Refit
1.Ensure solenoid and directional control valve
are clean.
2.Fit new 'O' ring to base of directional control
valve.
3.Fit solenoid to directional control valve, with
arrow on solenoid pointing up and connector in
correct position.
4.Fit new 'O' ring to solenoid securing cap. Fit cap
to solenoid but do not tighten at this stage.
5.Fit 3 bolts securing valve block to chassis and
tighten to 18 Nm (13 lbf.ft) .
6.Tighten solenoid securing cap to 11 Nm (8
lbf.ft) .
7.Connect multiplug to solenoid.
8.Lower vehicle.