1997 JAGUAR XJ6 sensor

12Remove the four balljoint retaining bolts
(see illustration).
13If the dust boot is damaged, pry it out
(see illustration).
14Remove the balljoint.
15Refitting is the reverse of removal. Tighten
the balljoint bolts and the ball stud nut to the
torque listed in this Chapter’s Specifications.
16Remove the jack from under the control
arm, refit the front wheel. Lower the vehicle
and tighten the wheel nuts to the torque listed
in the Chapter 1 Specifications.
6 Steering knuckle-
removal and refitting
3
1Loosen the wheel nuts, raise the front of the
vehicle and place it securely on axle stands.
Remove the wheel.
2Remove the front brake caliper and
mounting bracket (see Chapter 9). Do not
disconnect the brake hose. Hang the caliper
out of the way with a piece of wire.
3Remove the brake disc (see Chapter 9).
4Remove the ABS sensor (see illustration).
5Remove the brake shield (see illustration).
6Disconnect the tie-rod end from the
steering knuckle (see Section 15).
7Disconnect the upper and lower balljoints
from the steering knuckle (see Section 5).
8Remove the steering knuckle.
9Refitting is the reverse of removal. Tighten
the balljoint nuts and the tie-rod end nuts to the
specified torque. Tighten the brake fasteners to
the torque values listed in the Chapter 9
Specifications.
7 Upper control arm-
removal and refitting
3
1Loosen the wheel nuts, raise the vehicle
and support it securely on axle stands.
Remove the wheel.
2Support the lower control arm with a trolley
jack (see illustration 4.2).
3Disconnect the upper balljoint from the
steering knuckle (see Section 5).4If you’re removing the right upper control
arm on a vehicle equipped with the power
hydraulic system, remove the three Torx
screws which attach the accumulator (see
illustration)and push the assembly aside just
far enough to clear the pivot bolt.
5Remove the upper control arm pivot bolt
and nut (see illustration). When removing the
nut, note the number of washers used and the
order in which they’re installed. Put these
parts in a plastic bag.
6Remove the upper control arm. Inspect the
bushings at either end of the arm and renew
them if they’re damaged or worn.
7Refitting is the reverse of removal. Be sure
to refit the washers in the same order in which
they were removed. Raise the suspensionwith the trolley jack to simulate normal ride
height, then tighten the upper control arm
pivot bolt and nut to the torque listed in this
Chapter’s Specifications.
8 Coil spring (front)-
removal and refitting
3
Warning: The coil springs cannot
be removed without a special
spring compressor tool (Jaguar
tool JD115). Do not try to remove
a coil spring without this special tool. If you
do, you could be seriously injured.
1Loosen the wheel nuts, raise the vehicle
Suspension and steering systems 10•5
10
5.11 Strike the steering knuckle in this
area to pop the lower ball stud loose from
the steering knuckle5.12 To detach the lower balljoint from the
lower control arm, remove these four bolts
(arrowed)5.13 To detach the dust boot from the
steering knuckle, pry the lower lip of the
boot out of its groove in the knuckle
6.5 To detach the brake shield from the
steering knuckle, remove these three
screws (arrowed)6.4 To detach the ABS sensor from the
steering knuckle, remove this bolt
7.4 Remove these three Torx screws
(arrowed) and move the accumulator
assembly to the side a little to provide
clearance for pulling out the pivot bolt7.5 To detach the upper control arm from
the crossmember, remove the nut (at the
rear) and pull the bolt out from the front;
note the fitted order of the spacer washers
3261 Jaguar XJ6

5The shock/coil spring assemblies must be
dismantled, and the coil springs installed on
the new shocks. Although the shock/coil
spring assembly is similar in appearance to
the a MacPherson strut/coil spring assembly,
the spring on this unit is much stiffer.
Therefore, DO NOT attempt to take apart this
unit yourself with a strut spring compressor
tool. Instead, take the unit to a Jaguar dealer
service department or to a Jaguar specialist
workshop and have the springs installed on
the new shocks by professionals.6If you are retrofitting conventional shocks -
rather than refitting the same or another pair
of self-levelling shocks - unplug the electrical
connector at the ride height sensor, and fill
the connector with silicone (see illustration)
to prevent it from shorting out and causing
electrical problems. Then disconnect and
remove all hydraulic lines (see illustrations).
7Refitting is the reverse of removal. Be sure
to tighten all fasteners to the torque values
listed in this Chapter’s Specifications.
8Remove the jack supporting the controlarm, refit the rear wheels and lower the
vehicle.
9Tighten the rear wheel nuts to the torque
listed in the Chapter 1 Specifications.
10If you retrofitted conventional shocks to a
vehicle formerly equipped with the self-
levelling rear suspension system, disconnect
the forward end of the hydraulic line from the
valve block and refit the plug included in the
kit (see illustrations). Then finish removing
the forward section of hydraulic line and the
brackets for the line (see illustration).
Suspension and steering systems 10•7
10
10.6a Where applicable, unplug the
connector to the ride height sensor and fill
the connector with silicone . . .10.6b . . . then disconnect and remove
both valve blocks . . .10.6c . . . and remove all associated
plumbing, including the metal line (arrow) to
the valve block in the engine compartment
3261 Jaguar XJ6 10.3 To detach the bottom of the shock absorber/coil spring from
the control arm, remove this nut and bolt, then pull out the bolt
10.4 To detach the top of the shock absorber/coil spring from the
body, remove these bolts (arrowed) - not all bolts are visible here
10.10a After the vehicle has been lowered,
disconnect the forward end of the
hydraulic line from the valve block . . .10.10b . . . refit the plug included in the
retrofit kit . . .10.10c . . . then remove these bracket
screws (arrowed), the brackets and the
forward section of hydraulic line

11If you installed another pair of self-
levelling shocks, or removed and installed the
same pair of self-levelling shocks, be sure to
top up the power hydraulic system reservoir
(see Chapter 1).
11 Hub carrier (rear)-
removal and refitting
4
1Loosen the wheel nuts, raise the rear of the
vehicle and support it securely on axle stands.
Remove the wheel.
2Remove the rear caliper and brake pads,
the caliper bracket, the brake disc, the
handbrake cable and the handbrake shoe
assembly (see Chapter 9).
3Disconnect the outer end of the propshaft
from the hub carrier (see Chapter 8).
4Remove the ABS sensor, the ABS harness
clip and cut off the cable tie which secures the
ABS harness to the carrier (see illustration).
5Remove the nut and bolt which attach the
carrier to the control arm (see illustration).
6Remove the hub carrier assembly.
7Refitting is the reverse of removal. Be sure
to tighten all fasteners to the torque values
listed in this Chapter’s Specifications.
12 Hub and bearing (rear)-
renewal
4
If you want to renew the rear hub and
bearing assembly (or the ABS trigger wheel),
remove the hub carrier (see Section 11), then
take the carrier to a Jaguar dealer service
department or to an automotive machine
workshop. These parts require a hydraulic
press and special fixtures to dismantle and
reassemble.
13 Control arm (rear)-
removal and refitting
4
1Loosen the wheel nuts, raise the rear of the
vehicle and support it securely on axle stands.
Remove the wheel.
2Remove the rear caliper and brake pads,
the caliper bracket, the brake disc, the
handbrake cable and the handbrake shoe
assembly (see Chapter 9).
3Disconnect the outer end of the propshaft
from the hub carrier (see Chapter 8).
4Disconnect the lower end of the shock
absorber/coil spring assembly from the
control arm (see Section 10).
5Remove the hub carrier (see Section 11).
6Remove the control arm pivot bolt nut (see
illustration).
7Support the differential/crossmember
assembly with a trolley jack. Place a block of
wood between the jack head and the
differential to protect the differential.
Disconnect the lower end of the differential
tie-bar (see illustration)and carefully lower
the differential crossmember just enough toallow the control arm pivot bolt to be pulled
out to the rear without hitting the boot well.
8Remove the control arm.
9Inspect the control arm pivot bolt bushings.
If they’re cracked, dried out or torn, take the
arm to an automotive machine workshop and
have them replaced.
10Refitting is the reverse of removal. Tighten
all suspension fasteners to the torque listed in
this Chapter’s Specifications. Tighten all
brake fasteners to the torque listed in the
Chapter 9 Specifications.
14 Steering wheel-
removal and refitting
1
Warning: If your car is equipped
with an airbag, do not attempt
this procedure. Have it done by a
dealer service department or
other qualified repair workshop.
1Disconnect the negative battery cable.
Caution: If the radio in your vehicle is
equipped with an anti-theft system, make
10•8 Suspension and steering systems
13.6 Hold the pivot bolt and unscrew
the nut13.7 Remove this nut (arrowed) and bolt
from the lower end of each tie-bar (right
above the control arm pivot)
3261 Jaguar XJ6 11.4 Before detaching the hub carrier from the rear control arm,
remove the ABS sensor (left arrow), detach the ABS harness clip
(right arrow) and cut the cable tie securing the harness
11.5 To detach the hub carrier from the rear control arm, remove
the carrier-to-control arm nut and bolt

to earth somewhere in that area, probably
where the insulation has rubbed through. The
same test can be performed on each
component in the circuit, even a switch.
Earth check
Perform an earth test to check whether a
component is properly earthed. Disconnect
the battery and connect one lead of a self-
powered test light, known as a continuity
tester, to a known good earth. Connect the
other lead to the wire or earth connection
being tested. If the bulb goes on, the earth is
good. If the bulb does not go on, the earth is
not good.
Continuity check
A continuity check is done to determine if
there are any breaks in a circuit - if it is
passing electricity properly. With the circuit off
(no power in the circuit), a self-powered
continuity tester can be used to check the
circuit. Connect the test leads to both ends of
the circuit (or to the “power” end and a good
earth), and if the test light comes on the circuit
is passing current properly. If the light doesn’t
come on, there is a break somewhere in the
circuit. The same procedure can be used
to test a switch, by connecting the continuity
tester to the power in and power out sides of
the switch. With the switch turned On, the test
light should come on.
Finding an open circuit
When diagnosing for possible open circuits,
it is often difficult to locate them by sight
because oxidation or terminal misalignment
are hidden by the electrical connectors.
Merely wiggling an electrical connector on a
sensor or in the wiring harness may correct
the open circuit condition. Remember this
when an open circuit is indicated when
diagnosing a circuit. Intermittent problems
may also be caused by oxidised or loose
connections.Electrical fault finding is simple if you keep
in mind that all electrical circuits are basically
electricity running from the battery, through
the wires, switches, relays, fuses and fusible
links to each electrical component (light bulb,
motor, etc.) and to earth, from which it is
passed back to the battery. Any electrical
problem is an interruption in the flow of
electricity to and from the battery.
3 Fuses- general information
The electrical circuits of the vehicle are
protected by a combination of fuses, circuit
breakers and In-line fuses. The fuse blocks
are located in the left and right side kick
panels and in the centre console glove box
(see illustrations).
Each of the fuses is designed to protect a
specific circuit, and the various circuits are
identified on the fuse panel cover.
Miniaturised fuses are employed in the fuse
blocks. These compact fuses, with blade
terminal design, allow fingertip removal and
renewal. If an electrical component fails,
always check the fuse first. The best way tocheck the fuses is with a test light. Check for
power at the exposed terminal tips of each
fuse. If power is present on one side of the
fuse but not the other, the fuse is blown. A
blown fuse can be confirmed by visual
inspection (see illustration).
Be sure to renew blown fuses with the
correct type. Fuses of different ratings are
physically interchangeable, but only fuses of
the proper rating should be used. Replacing a
fuse with one of a higher or lower value than
specified is not recommended. Each electrical
circuit needs a specific amount of protection.
The amperage value of each fuse is moulded
into the fuse body.
If the renewal fuse immediately fails, don’t
renew it again until the cause of the problem
is isolated and corrected. In most cases, this
will be a short circuit in the wiring caused by a
broken or deteriorated wire.
4 In-line fuses-
general information
Some circuits are protected by in-line
fuses. In-line fuses are used in such circuits
as the windscreen wiper system, headlight
12•2 Body electrical system
3261 Jaguar XJ6 3.1a The left side fusebox is located in the passenger’s side kick
panel, behind the fuse panel cover
3.1b The right side fusebox is located in the driver’s side kick
panel, behind the fuse panel cover
3.1c A third fusebox is located in the
centre console glove box3.3 When a fuse blows, the metal element
between the terminals melts - the fuse on
the left is blown, the one on the right is ok

Later models are equipped with a
Supplemental Restraint System (SRS), more
commonly known as an airbag. This system is
designed to protect the driver, and on 1994
models, the passenger from serious injury in
the event of a head-on or frontal collision. It
consists of an airbag module in the centre of
the steering wheel and a passenger airbag
module on the right side of the dash above
the glove box on 1994 models.
The airbag modules contain an inflater and
a sensor assembly which activates from
impact energy that is transmitted through the
body and steering column upon impact or
collision.
DO NOT try to dismantle or remove any
component in the vicinity of the steering
column or instrument panel on models
equipped with air bags. Serious personalinjury or damage may result. The
manufacturer recommends that, on airbag
equipped models, service which requires
removal of any component in the vicinity of
the instrument panel or steering column
should be left to a dealer service department
or other properly equipped repair facility
because of the special tools and techniques
required to disable the air bag system.
29 Wiring diagrams-
general information
Since it isn’t possible to include a complete
wiring diagram for every year covered by this
manual, the following diagrams are those that
are typical and most commonly needed.Prior to diagnosing any circuits, check the
fuse and circuit breakers (if equipped) to make
sure they are in good condition. Make sure
the battery is properly charged and has clean,
tight cable connections (see Chapter 1).
When checking the wiring system, make
sure that all electrical connectors are clean,
with no broken or loose pins. When
unplugging an electrical connector, do not
pull on the wires, only on the connector
housings themselves.
Body electrical system 12•15
12
3261 Jaguar XJ6 Wiring diagrams commence overleaf

3261 Jaguar XJ6
Fault findingREF•13
1 Engine
Engine will not rotate when attempting to start
m mBattery terminal connections loose or corroded (Chapter 1).
m mBattery discharged or faulty (Chapter 1).
m mDamaged left rear window harness shorting against glass rail
inside door, causing battery to drain (Chapter 12).
m mAutomatic transmission not completely engaged in Park
(Chapter 7).
m mBroken, loose or disconnected wiring in the starting circuit
(Chapters 5 and 12).
m mStarter motor pinion jammed in flywheel ring gear (Chapter 5).
m mStarter solenoid faulty (Chapter 5).
m mStarter motor faulty (Chapter 5).
m mIgnition switch faulty (Chapter 12).
m mStarter pinion or flywheel teeth worn or broken (Chapter 5).
m mInternal engine problem (Chapter 2B).
m mInertia switch activated (Chapter 12).
m mStarter relay defective (Chapter 5).
Engine rotates but will not start
m
mFuel tank empty.
m mBattery discharged (engine rotates slowly) (Chapter 5).
m mBattery terminal connections loose or corroded (Chapter 1).
m mLeaking fuel injector(s), faulty fuel pump, pressure regulator, etc.
(Chapter 4).
m mFuel not reaching fuel injection system (Chapter 4).
m mIgnition components damp or damaged (Chapter 5).
m mFuel injector stuck open (Chapter 4).
m mWorn, faulty or incorrectly gapped spark plugs (Chapter 1).
m mBroken, loose or disconnected wiring in the starting circuit
(Chapter 5).
m mLoose distributor is changing ignition timing (Chapter 1).
m mBroken, loose or disconnected wires at the ignition coil or faulty
coil (Chapter 5).
m m1988 and 1989 models may have electrical connector damage
between the fuel pump relay and the fuel pump (Chapter 12).
m mCoolant temperature sensor shorting on bonnet liner (Chapter 11).
m mDefective Mass Airflow (MAF) sensor (Chapter 6).
Engine hard to start when cold
m
mBattery discharged or low (Chapter 1).
m mFuel system malfunctioning (Chapter 4).
m mInjector(s) leaking (Chapter 4).
m mDistributor rotor carbon tracked (Chapter 5).
m mWater enters the air cleaner housing near the left front wheel arch
(Chapter 4).
Engine hard to start when hot
m mAir filter clogged (Chapter 1).
m mFuel not reaching the fuel injection system (Chapter 4).
m mCorroded battery connections, especially ground (Chapter 1).
m mFuel vaporises at fuel pump inlet. Refit dual fuel pumps
(Chapter 4).
m mFuel vapours from charcoal canister enter intake during idle and
cause idling, stalling and starting problems (Chapter 6).
Starter motor noisy or excessively rough in
engagement
m mPinion or flywheel gear teeth worn or broken (Chapter 5).
m mStarter motor mounting bolts loose or missing (Chapter 5).
Engine starts but stops immediately
m
mLoose or faulty electrical connections at distributor, coil or
alternator (Chapter 5).
m mInsufficient fuel reaching the fuel injector(s) (Chapters 1 and 4).
m mDamaged fuel injection system speed sensors (Chapter 5).
m mFaulty fuel injection relays (Chapter 5).
m mLeaking threaded adapter on the EGR valve - where fitted
(Chapter 6)
Oil puddle under engine
m mSump gasket and/or sump drain bolt seal leaking (Chapter 2).
m mOil pressure sending unit leaking (Chapter 2).
m mValve cover gaskets leaking (Chapter 2).
m mEngine oil seals leaking (Chapter 2).
m mCylinder head rear plate gasket leaking (Chapter 2).
m mAlternator mounting bolt threads leaking oil (Chapter 5).
m mOil cooler or oil cooler lines leaking (Chapter 3).
Engine misses while idling or idles erratically
m
mVacuum leakage (Chapter 2).
m mAir filter clogged (Chapter 1).
m mFuel pump not delivering sufficient fuel to the fuel injection system
(Chapter 4).
m mLeaking head gasket (Chapter 2).
m mTiming belt/chain and/or sprockets worn (Chapter 2).
m mCamshaft lobes worn (Chapter 2).
m mEGR valve stuck open - where fitted (Chapter 6).
Engine misses at idle speed
m
mSpark plugs worn or not gapped properly (Chapter 1).
m mFaulty spark plug leads (Chapter 1).
m mVacuum leaks (Chapter 1).
m mIncorrect ignition timing (Chapter 5).
m mUneven or low compression (Chapter 2).
m mRestricted EGR vacuum hose - where fitted (Chapter 6).
Engine misses throughout driving speed range
m
mFuel filter clogged and/or impurities in the fuel system (Chapter 1).
m mLow fuel output at the injectors (Chapter 4).
m mFaulty or incorrectly gapped spark plugs (Chapter 1).
m mIncorrect ignition timing (Chapter 5).
m mCracked distributor cap, disconnected distributor wires or
damaged distributor components (Chapter 1).
m mLeaking spark plug leads (Chapter 1).
m mFaulty emission system components (Chapter 6).
m mLow or uneven cylinder compression pressures (Chapter 2).
m mWeak or faulty ignition system (Chapter 5).
m mVacuum leak in fuel injection system, intake manifold or vacuum
hoses (Chapter 4).
m mCrankshaft sensor teeth damaged or missing (see Chapter 12).
m mDistributor installed incorrectly (see Chapter 5)
Engine stumbles on acceleration
m
mSpark plugs fouled (Chapter 1).
m mFuel injection system malfunctioning (Chapter 4).
m mFuel filter clogged (Chapters 1 and 4).
m mIncorrect ignition timing (Chapter 5).
m mIntake manifold air leak (Chapter 4).
m mCollapsed or damaged fuel tank caused by blocked EVAP system
- where fitted (see Chapter 6).

3261 Jaguar XJ6
Fault findingREF•15
4 Automatic transmission
Note:Due to the complexity of the automatic transmission, it is difficult
for the home mechanic to properly diagnose and service this
component. For problems other than the following, the vehicle should
be taken to a dealer or transmission workshop.
Fluid leakage
m mAutomatic transmission fluid is a deep red colour. Fluid leaks
should not be confused with engine oil, which can easily be blown
by air flow to the transmission.
m mTo pinpoint a leak, first remove all built-up dirt and grime from the
transmission housing with degreasing agents and/or steam
cleaning. Then drive the vehicle at low speeds so air flow will not
blow the leak far from its source. Raise the vehicle and determine
where the leak is coming from. Common areas of leakage are:
a) Sump pan (Chapters 1 and 7)
b) Dipstick/filler tube (see below)
c) Transmission fluid cooler lines (Chapter 7)
d) Speedometer sensor (Chapter 7)
m mMake sure the dipstick is a tight fit inside the filler tube. If the seal
at the top of the dipstick is worn or damaged, replace the seal or
the dipstick. If fluid continues to leak from the top of the dipstick
tube, inspect the breather, which is a plastic cap secured by a clip
to the top of the extension housing. This breather can be plugged
by the noise-deadening foam installed in the transmission tunnel,
causing transmission fluid to leak from the top of the dipstick
tube.
Transmission fluid brown or has a burned smell
m mTransmission fluid burned (Chapter 1).
Shift cable problems
m
mChapter 7 deals with adjusting the shift cable. Common problems
which may be attributed to a poorly adjusted shift cable are:
a) Engine starting in gears other than Park or Neutral.
b) Indicator on shift lever pointing to a gear other than the one
actually being used.
c) Vehicle moves when in Park.
m mRefer to Chapter 7 for the shift cable adjustment procedure.
Transmission will not downshift
with accelerator pedal pressed to the floor
m mKickdown cable out of adjustment (Chapter 7).
Engine will start in gears
other than Park or Neutral
m mNeutral start/reversing light switch malfunctioning (Chapter 7).
m mShift cable out of adjustment (Chapter 7).
Transmission slips, shifts roughly, is noisy,
or has no drive in forward or reverse gears
m mThere are many probable causes for the above problems, but the
home mechanic should be concerned with only one possibility -
fluid level. Before taking the vehicle to a dealer service department
or transmission repair workshop, check the level and condition of
the fluid as described in Chapter 1. Correct the fluid level as
necessary or change the fluid if needed. If the problem persists,
have a professional diagnose the probable cause.
5 Brakes
Note:Before assuming that a brake problem exists, make sure that:
a) The tyres are in good condition and properly inflated (Chapter 1).
b) The front end alignment is correct (Chapter 10).
c) The vehicle is not loaded with weight in an unequal manner.
Vehicle pulls to one side during braking
m mIncorrect tyre pressures (Chapter 1).
m mFront end out of line (have the front end aligned).
m mUnmatched tyres on same axle.
m mRestricted brake lines or hoses (Chapter 9).
m mMalfunctioning caliper assembly (Chapter 9).
m mLoose suspension parts (Chapter 10).
m mLoose calipers (Chapter 9).
m mBrake pads contaminated with oil or grease (Chapter 9).
Noise (high-pitched squeal
when the brakes are applied)
m mFront and/or rear disc brake pads worn out. The noise comes from
the wear sensor rubbing against the disc. Replace pads with new
ones immediately (Chapter 9).
Brake roughness or chatter (pedal pulsates)
m mExcessive lateral disc runout (Chapter 9).
m mParallelism not within specifications (Chapter 9).
m mUneven pad wear caused by caliper not sliding due to improper
clearance or dirt (Chapter 9).
m mDefective disc (Chapter 9).
Excessive pedal effort required to stop vehicle
m
mMalfunctioning power brake servo (Chapter 9).
m mPartial system failure (Chapter 9).
m mExcessively worn pads (Chapter 9).
m mPiston in caliper stuck or sluggish (Chapter 9).
m mBrake pads contaminated with oil or grease (Chapter 9).
m mNew pads installed and not yet seated. It will take a while for the
new material to seat against the disc.
m mAccumulator in power hydraulic system defective (see a Jaguar
dealer).
Excessive brake pedal travel
m mPartial brake system failure (Chapter 9).
m mInsufficient fluid in master cylinder (Chapters 1 and 9).
m mAir trapped in system (Chapters 1 and 9).
Dragging brakes
m
mMaster cylinder pistons not returning correctly (Chapter 9).
m mRestricted brakes lines or hoses (Chapters 1 and 9).
m mIncorrect handbrake adjustment (Chapter 9).
Grabbing or uneven braking action
m
mMalfunction of power brake servo unit (Chapter 9).
m mBinding brake pedal mechanism (Chapter 9).
m mBrake pads contaminated with oil or grease (Chapter 9).

3261 Jaguar XJ6
REF•20Glossary of technical terms
GGapThe distance the spark must travel in
jumping from the centre electrode to the side
electrode in a spark plug. Also refers to the
spacing between the points in a contact
breaker assembly in a conventional points-
type ignition, or to the distance between the
reluctor or rotor and the pickup coil in an
electronic ignition.
GasketAny thin, soft material - usually cork,
cardboard, asbestos or soft metal - installed
between two metal surfaces to ensure a good
seal. For instance, the cylinder head gasket
seals the joint between the block and the
cylinder head.
GaugeAn instrument panel display used to
monitor engine conditions. A gauge with a
movable pointer on a dial or a fixed scale is an
analogue gauge. A gauge with a numerical
readout is called a digital gauge.
HHalfshaftA rotating shaft that transmits
power from the final drive unit to a drive
wheel, usually when referring to a live rear
axle.
Harmonic balancerA device designed to
reduce torsion or twisting vibration in the
crankshaft. May be incorporated in the
crankshaft pulley. Also known as a vibration
damper.
HoneAn abrasive tool for correcting small
irregularities or differences in diameter in an
engine cylinder, brake cylinder, etc.
Hydraulic tappetA tappet that utilises
hydraulic pressure from the engine’s
lubrication system to maintain zero clearance
(constant contact with both camshaft and
valve stem). Automatically adjusts to variation
in valve stem length. Hydraulic tappets also
reduce valve noise.
IIgnition timingThe moment at which the
spark plug fires, usually expressed in the
number of crankshaft degrees before the
piston reaches the top of its stroke.
Inlet manifoldA tube or housing with
passages through which flows the air-fuel
mixture (carburettor vehicles and vehicles with
throttle body injection) or air only (port fuel-
injected vehicles) to the port openings in the
cylinder head.
JJump startStarting the engine of a vehicle
with a discharged or weak battery by
attaching jump leads from the weak battery to
a charged or helper battery.
LLoad Sensing Proportioning Valve (LSPV)A
brake hydraulic system control valve that
works like a proportioning valve, but also
takes into consideration the amount of weight
carried by the rear axle.
LocknutA nut used to lock an adjustment
nut, or other threaded component, in place.
For example, a locknut is employed to keep
the adjusting nut on the rocker arm in
position.
LockwasherA form of washer designed to
prevent an attaching nut from working loose.
MMacPherson strutA type of front
suspension system devised by Earle
MacPherson at Ford of England. In its original
form, a simple lateral link with the anti-roll bar
creates the lower control arm. A long strut - an
integral coil spring and shock absorber - is
mounted between the body and the steering
knuckle. Many modern so-called MacPherson
strut systems use a conventional lower A-arm
and don’t rely on the anti-roll bar for location.
MultimeterAn electrical test instrument with
the capability to measure voltage, current and
resistance.
NNOxOxides of Nitrogen. A common toxic
pollutant emitted by petrol and diesel engines
at higher temperatures.
OOhmThe unit of electrical resistance. One
volt applied to a resistance of one ohm will
produce a current of one amp.
OhmmeterAn instrument for measuring
electrical resistance.
O-ringA type of sealing ring made of a
special rubber-like material; in use, the O-ring
is compressed into a groove to provide the
sealing action.
Overhead cam (ohc) engineAn engine with
the camshaft(s) located on top of the cylinder
head(s).Overhead valve (ohv) engineAn engine with
the valves located in the cylinder head, but
with the camshaft located in the engine block.
Oxygen sensorA device installed in the
engine exhaust manifold, which senses the
oxygen content in the exhaust and converts
this information into an electric current. Also
called a Lambda sensor.
PPhillips screwA type of screw head having a
cross instead of a slot for a corresponding
type of screwdriver.
PlastigageA thin strip of plastic thread,
available in different sizes, used for measuring
clearances. For example, a strip of Plastigage
is laid across a bearing journal. The parts are
assembled and dismantled; the width of the
crushed strip indicates the clearance between
journal and bearing.
Propeller shaftThe long hollow tube with
universal joints at both ends that carries
power from the transmission to the differential
on front-engined rear wheel drive vehicles.
Proportioning valveA hydraulic control
valve which limits the amount of pressure to
the rear brakes during panic stops to prevent
wheel lock-up.
RRack-and-pinion steeringA steering system
with a pinion gear on the end of the steering
shaft that mates with a rack (think of a geared
wheel opened up and laid flat). When the
steering wheel is turned, the pinion turns,
moving the rack to the left or right. This
movement is transmitted through the track
rods to the steering arms at the wheels.
RadiatorA liquid-to-air heat transfer device
designed to reduce the temperature of the
coolant in an internal combustion engine
cooling system.
RefrigerantAny substance used as a heat
transfer agent in an air-conditioning system.
R-12 has been the principle refrigerant for
many years; recently, however, manufacturers
have begun using R-134a, a non-CFC
substance that is considered less harmful to
the ozone in the upper atmosphere.
Rocker armA lever arm that rocks on a shaft
or pivots on a stud. In an overhead valve
engine, the rocker arm converts the upward
movement of the pushrod into a downward
movement to open a valve.
Adjusting spark plug gap
Plastigage
Gasket