1998 JAGUAR X308 body

Vehicle Dynamic Suspension - Vehicle Dynamic Suspension
Description an
d Operation
Front Sho

ck Absorbers

The front shock absorber
comprises:
A

coil-type road spring, mounted between the lower wish
bone spring pan and the front suspension crossbeam;
different spring rates are used according to model.
A
telescopic, hydraulically controlled, damper mounte
d between the lower wishbone and the vehicle body.
It
em
De
scription
1Front

suspension crossbeam
2Front

hub assembly
3Ro

ad spring
4Dam

per

The rear shock ab
sorber comprises:
A
c
oil-type road spring mounted between the lower wish
bone and the upper spring seat on the vehicle body;
different spring rates are used according to model.
A te
lescopic, hydraulically controlled, damper, co-axial wi
th the road spring, mounted between the lower wishbone
and the upper spring seat on the vehicle body.
Damp
ing Principle
D
a
mping is achieved by controlling the flow of fluid from one
end of the damping chamber to the other. The more the flow
of fluid is restricted, the firmer the damping action.
Ite
m
De
scr
iption
1Dam
p
er
2Ro
ad s
pring
3Lower wishbon
e
4Upper sprin
g seat

Rear Shock A
b
sorbers

The
Nivomat ride levelling system improves ride quality by al
lowing the use of softer road springs, while controlling the
effects on the suspension of a fully laden vehicle. The system uses special rear dampers in place of the normal units. There
are no other components in th e system. The ride levelling system is comple tely automatic, requiring no input from the
driver.
Ride levelling may be specified as an opti on on certain models; it is not available in north American markets. Ride levelling
and adaptive damping are mu tually exclusive options.
The Nivomat damper:
Su
pplements the load-carrying capacity of th
e road springs at high vehicle loads.
Uses road inputs to the
suspension to power the levelling function.
De

tects suspension height dire
ctly from road wheel travel.
Provi
des load-dependent spring rates; the ac
cumulator gas pressure increases with load.
Pr
ovides load-dependent damping; the fluid pressure increases with load.
Op

eration
F
ollowing an increase in vehicle loading,
the dampers adapt to maintain the height of the vehicle within its design range.
The system uses road inputs to the suspension to power the levelling action, and requires up to approximately two
kilometers of travel, following a change in load, to complete the process.
Normal movement of the suspension caus es a pumping action to occur within the damper, as a result of extension and
compression of the pump rod in the pump chamber. Hydraulic fluid is pumped from the pump cham ber into a high pressure
gas accumulator. The increase in gas pressure augments the force developed between th e vehicle axle and the body,
thereby providing lift.
It
em
De
scription
1Pi

ston rod
2Pum

p chamber
3High

pressure
gas accumulator
4Diaphragm
5Co
ntrol orifice
6Pump rod
7Low pressure gas ch

amber
8Low pressure oil

reservoir


Ride Levelling

R
equire no adjustment and are non-serviceable items.
Accelerometers


The three accelerometers:
Sense veh
icle body movement.
Gen

erate an analogue voltag
e (maximum +5 volts) proportional to body movement.
Pr
ovide inputs to the adapti
ve damping control module.
The two vertical acce lerometers are mounted on the bulkhead and in the trunk.
The lateral accelerometer is mounted in the ECM housing.
Ada
ptive Damping Control Module (ADCM)

The ADCM
:
Is

mounted on the fascia support bracket.
Controls the four adaptiv

e dampers in re
sponse to analogue and digital inputs.
It
em
De
scription
1Battery su

pply
2Ignition su

pply
3Ground
4Input from verti

cal accelerometer, front
5Input from verti

cal accelerometer, rear
6Input from later

al accelerometer
7F

ootbrake operation signal
8Vehi

cle speed input
9D

amper control signals
10Ou

tput to message center
11D

iagnostic connector serial link

Is hard-wi
red to the instrume
nt cluster message center.
Is hard
-wired to the J1962 diagnostic connector.
Op
era
tion
Th
e
system selects the soft or
firm damper setting according to the current ro ad and driving conditions, to optimise vehicle
ride and handling.
With the vehicle stationary, the dampers are in the firm setting, but will normally switch to the soft setting when the vehicle
exceeds 8 km/h (5 mile/h); all dampers are switched simultaneously.
Sudden movement of the vehicle body, in response to road inputs, is detected by the vertical accelerometers, and the ADCM
switches the dampers to the firm setting to give improved damping of the resultant oscillations.
When cornering forces are detected by th e lateral accelerometer, the ADCM switches the dampers to the firm setting to
reduce the roll rate an d improve wheel control.
After the event has passed, the dampers revert to the soft setting.
When the footbrake is applied, the ADCM re ceives a signal and calculates the rate of vehicle deceleration. If the deceleration
rate is greater than a certain threshold, the dampers are switched to the firm setting to reduce the pitch rate and improve
wheel control.
If a system failure occurs, the ADCM grounds the output line to the instrument cluster message center, which displays a
text warning SUSPENSION FAULT and illuminates the amber warning lamp. Under fault conditions the system always fails to
the firm setting, so that the vehicle will be safe to drive un der all road and driving conditions.
Connector Pin Identity Chart for EM068

Pin
Number
Ci
rcui
t
Circuit Functi
on
1System erro
r output to instrument
cluster
2Not
used
3O/
P a
ccelerometer ground
4 to

9
Not
used
10K-
li
ne to diagnostic socket
11Ignition su
pply +12V
12Not
used
13Control signal (+ve) output
to l
eft-hand rear damper
14Control signal (+ve) output
to right-hand front damp
er
15Control signal (+ve) output
to right-hand rear
damper
16
a
nd 17
No
t
used
18Ground
19No
t
used
20Lateral
accelerometer i
nput
21Front vertical ac
celerometer in
put
22Rear vertical
acce
lerometer input
23No
t
used
24R
o
ad speed input from
instrument cluster
25Power output +5V to suppl y accelerometers
26Brake peda
l input

Vehicle Dynamic Suspension - Vehicle Dynamic Suspension
Diagn
osis and Testing
Refer to the PDU User Guide for details of diagnosing and testing the Adaptive Damping System. The PDU interrogates the
ADCM directly via the K and L lines to the J1962 diagnostic socket.
The PDU will give an indication of the integrity of each electron ic and electrical component. It will indicate, for example, that
the accelerometers are not broken, but not that they functionin g correctly when the vehicle is in motion. However, it is
exceptional for an accelero meter to function incorrectly in its dynamic mode if it is proved to be functioning when static.
Basic Checks
The accele
rometers have the following ch
aracteristics. At 0g (no movement of the body) each vertical accelerometer
outputs approximately 2.5V steady voltage; the lateral acce lerometer outputs approximately 1.5V. The voltage output due
to body movement is proportional to acceleration in the acceleration axis, up to approximately 4.5V and down to
approximately 0.5V.
Before changing any component, refer to the circuit diagrams and check the cont inuity of relevant harness circuits; in some
instances, the PDU will not different iate between a faulty component an d a damaged connection or wiring.
Check the following fuses:
En
gine compartment fuse
box, fuse F5 (10A).
Engine m
anagement fuse
box, fuse F1 (20A).
Check the following ADCM input/output lines:
Sy stem erro
r output from the ADCM
to the instrument cluster.
Vehicl
e speed output from the inst
rument cluster to the ADCM.
Foo
tbrake signal to the ADCM.
Check any relevant connections to confirm that the connection is electrically sound and that a terminal pin has not been
pushed back into the connector shell, ie. not ma king a connection to its mating pin or socket.

Driveshaft -
Torques



Comp

onent
Nm
Bol
t
M12 - Jurid flexible coupling to
transmission and final drive flanges
75
-
88
Screw
-
Centre bearing to underbody
19
,5
- 26,5
Screw
-
Parking brake relay mounting bracket to underbody
19
,5
- 26,5_

Front Disc Brake -
Lubri
cants, Fluids, Sealants and Adhesives
Torques - Brembo Brakes
Torques
Brake Tube, Hoses and Bracket Torques
CAUTI
ON: Replacement of
nuts and bolts: Various thread-locking devices are used on nuts and bolts throughout the
vehicle. These devices restrict the number of times a nut or bolt can be used. See section 100-00 for information.


UnitS
pecification
Brake flu

id
ITT Supe
r Dot 4
Com

ponent
Nm
B

olt - anchor bracket to vertical link
18
0
Bo

lt - caliper to anchor bracket
DO
NOT REMOVE
Bleed n

ipple
12
-16
Hose u

nion to caliper
22
-26
Com

ponent
Nm
Bol

t - caliper carrier to vertical link
14
0
Guide

Pin - caliper housing to caliper carrier
25
-30
Com

ponent
Nm
Bleed n

ipple - front
4-
6
Bleed n

ipple - rear
8-1
1
Hose to fr

ont caliper
10
-14
Hose union to rear cal

iper - union bolt
30
-40
M1

0 hose locknut
15
-20
M10

brake tube female-nut
13
-17
M10

brake tube male-nut
13
-17
M12

brake tube male-nut
15
-20
M18

brake tube male-nut
22
-28
Brake tube clip retention

-bracket to body
4-
6