1998 JAGUAR X308 valve

Hiss (Swish)
Hiss or Val
ve Hiss is a high-frequency so
und coming from the steering gear when the system is loaded. It is a rushing or
"swish" noise that doesn't change frequency with RPM. Hiss is the general noise generated by the flow of hydraulic fluid
through restrictions in the steer ing system. Restrictions include the rotary stee ring valve, power steering tubes, connectors,
tuning orifices, etc. Hiss can be air- borne and structure-borne, but the structure-borne path through the steering
intermediate shaft is usually dominant.
Moan (Groan)
Moan is the general structu r
e-borne noise of the steering system. Moan is primarily transmitted to the driver via the body
structure through the pump mount, engine mounts, power steering lines and power steering brackets. On some vehicles,
moan is a load humming noise, often present when the wheel is turned and the system is loaded. It may change frequency
with engine RPM and if the sy stem is loaded or unloaded.
Rack Knock (R
ack Slap)
CAU
T
ION: DO NOT attempt to adjust the stee
ring gear yoke. Failure to follow this instruction will result in the steering
gear warranty to become invalid.
Rack Knock is a rattle sound an d steering wheel vibration caused by separation of the steering gear and pinion while driving
over bumps. It is a structure-borne noise transmitted throug h the intermediate shaft and column. Rack knock can also be
heard as a "thump" or impact noise that occurs with the vehicle stationary when the steering wheel is released from a
loaded position and allowed to return to rest . Noise occurs with the engine on or off.
Rattles
Ra
ttles are noises caused by knocking or hitting with components in the steering system. Steering rattles can occur in the
engine compartment, the suspension, or the passenger compartment . Rattles can be caused by loose parts, movable and
flexible parts, and improper clearances.
Squea k
s/Scrapes
Squeaks/Scrapes are noises due
to fri
ction or component rubbi
ng anywhere in the steering system. Squeaks/Scrapes have
appeared in steering linkages and jo ints, in column components and in co lumn and steering wheel trim parts.
Weep
We
ep is an air-borne noise, occasionally
generated when turning the steering across lock at a constant rate. When present
on a vehicle the noise, once initiated can often be maintained across a large proportion of the available steering movement.
Whistle
Wh
istle is similar to hiss but is louder and of a higher frequency. It is also more
of a pure tone noise than hiss. Whistle is
air-borne and is generated by a high flow rate of hydraulic fluid through a small restriction.
Zip

Zip n
o
ise is the air-borne noise
generated by power steerin g pump cavitation when power steering fluid does not flow freely
through the suction hose from the rese rvoir to the pump. Zip primarily occurs during cold weather at start-up.
Steering System Vibrations and Harshne
ss
Buzz
Buzz is a tactile rotary vi

bration felt in
the steering wheel for slow steering inputs. Buzz can also be called a grinding feel
and it is closely related to grunt and is caused by high system gain with low damping. Buzz is generally excited during
parking manoeuvres with low to medium speed steering input.

Power Steering -
Lubric
ants, Fluids, Sealants and Adhesives
Capacities
Torques


UnitSp
ecification
PAS flu
i
d
De
xr
on 3
UnitLi
t
ers
PAS syste
m1,0
PAS reservoi
r0,4
Com p
onent
Nm
Rac
k
mountin
g brac
ke
t to suspension crossbeam
40
- 50
PAS pump to front mounti
ng bracket
22
-
26
P
AS pu
mp assembly to cylinder block
38
-
48
Pul
l
ey to PAS pump
18
-
24
Hi
gh pressure hose to PAS pump22 -
28
Rack
pipe latch plate bolt8.5 -
11.5
R
e
servoir mounting bracket to body nuts
4 -

5
R
e
servoir mounting bracket clamp
4 -

5
Fluid cooler to body2.
5 -
3.5
Transfer pipe
to steering rack7 -
8
Transfer pipe
to hydraulic con
trol valve
7 -

8

Power Steering - Power Steering
Description an
d Operation

Parts List
The power steering system is a rack and pinion design, with an engine-dri ve n pump providing the steering assistance. The
system features variable steering assistance with vehicle spee d, a variable ratio steering rack, and a hydraulic control valve
which has a torsion bar arrangement giving improved center feel to the steering.
Absolute cleanliness must be observed wh en replenishing the fluid or dismantling any part of the system. If any major
component is renewed a new fluid rese rvoir must be fitted. New fluid from a sealed container must be used.
It
em
Par
t Number
De
scription
1—Steeri

ng rack assembly
2—Power as

sisted steering pump
3—F

luid reservoir
4—F

luid cooler
5—Hoses and pipework
6—In-

line quick-fit connector

The steering rack assembly :
Is mounted on the
rear face of the
front suspension crossbeam by two forg ed mounting brackets with resilient
bushes. The bushes are handed (pinion side and non-pinion side) and are orientated according to the vehicle range
application.
Convert s
the rotary motion of the steering wheel, via the steering gear pinion, to the lateral motion of the rack.
F
e
atures a variable ratio steering
rack with integral hydraulic po wer steering cylinder and piston.
Has a hydrauli
c control valve with Servotronic co
ntrol and positive center feel torsion bar.
The basic steering rack assembly is not serviceable. The following components are serviceable items:
Transfer pipework
.
Servotronic valve. Cent
ralizing cap.

O
u
ter ball joint.
Rac
k
gaiter.
Clips and

fittings.
Steering Rack Components
It e
m
Par
t
Number
De
scr
iption
1—Front
su
spension crossbeam
2—Steeri
ng rack housi
ng
3—Hydraulic

control valve housing
4—Moun
ting bracke
t
5—Gait
er

6—Tie
rod

7—O
u
ter ball joint

Steering R
a
ck Assembly

P
arts List
It

em
Par
t Number
De
scription
1—Steeri

ng rack
2—Hydrau

lic control valve
3—Torsio

n bar
4—Pin

ion
5—O

perating cylinder and piston
6—Inne

r ball joint
7—Tie

rod

P
arts List
The positive center-feel torsion bar improves the straight ahead feel of the steering in the region where very small amounts
of hydraulic pressure, and hence re action pressure, are generated.
The torsion bar assembly forms part of the hydraulic control valve assembly , and includes an axially pre-loaded metal
bellows spring, which is arranged co-axially with the torsion bar. The torsion bar is positively connected between the end
piece and the input shaft. One end of the bellows spring is attached to the input shaft, while the other end is attached to a
centering device. The centering device has two prism-shaped recesses with ca ged, guided, ball bearings arranged between
the recesses, and determines the zero-torsion position of the bellows spring.
On turning the steering wheel from the straight ahead position, the spring fo rces of the torsion bar assembly must be
overcome. Initially, the bellows spring produces substantial additional torsional resistance. However, after an angular
movement of approximately 0.2 degrees the torsional rigidity decreases and becomes similar to a conventional torsion bar.
It
em
Par
t Number
De
scription
1—End piece
2—Torsio

n bar
3—Caged ball bearing

s
4—Centering device
5—Bel

lows spring
6—In

put shaft


Positive Center-Feel Torsion Bar

Torsio
n Bar Components

P a
rts List
The supply and return pipes are secured to the hydraulic control valve housing by a latch-plate having a single fixing screw.
The latch-plate is captive to the supply pipe. Each pipe has an O-ri ng which is a serviceable item.
In-Line Quick-Fit Connector

Parts List

Ite
m
Par
t
Number
De
scr
iption
1—Return
pipe (RH drive)
2—Supply pipe (RH
drive)
3—Latc
h-plate
4—Latch-
plate securing screw
It
e
m
Par
t
Number
De
scr
iption
1—Qu
ic
k-fit connector
2—Return
pipe

Latch
-Plate Location

m
ember. The quick-fit connector O-rings are not serviceable.
Special tool JD 182 is required to disconnect the quick-fit connector.
Hydraulic System


P
arts List
Hydraulic System

Op
erating Principle
The rot
ary motion of the steering wheel is converted, via the st
eering rack pinion, to the lateral motion of the rack. Steering
assistance is provided by pressurized fluid being directed against a piston operating within the rack cylinder. Rack
movement is achieved by diffe rential pressures being applied on either si de of the rack piston, caused by unequal
restrictions within the hydraulic control valve.
The main components of the hydraulic control valve are the rota ry distributor, control sleeve and hydraulic reaction piston.
It
em
Par
t Number
De
scription
1—F

luid reservoir
2—Pum

p
3—Pressure and fl

ow limiting valve
4—Supply line
5—R

eturn line
6—Steeri

ng rack
7—Pin

ion
8—O

perating cylinder and piston
9—Hydrau

lic control valve
10—Hydraulic reaction

piston
11—Control

sleeve
12—R

otary distributor
13—F

luid cooler


A
quick-fit connector with double O-ring se
als is incorporated in the return line and is clipped to the right-hand chassis side