1993 FORD MONDEO cooling

compartment, but on Estate models, it is on
the right-hand side.
Some models are fitted with a headlight
levelling system, which is controlled by a knob
on the facia. On position “0”, the headlights
are in their base position, and on position “5”,
the headlights are in their maximum inclined
angle.
It should be noted that, when portions of
the electrical system are serviced, the cable
should be disconnected from the battery
negative terminal, to prevent electrical shorts
and fires.
Caution: When disconnecting the
battery for work described in the
following Sections, refer to
Chapter 5, Section 1.
Note:Refer to the precautions given in
“Safety first!” and in Section 1 of this Chapter
before starting work. The following tests relate
to testing of the main electrical circuits, and
should not be used to test delicate electronic
circuits (such as engine management systems,
anti-lock braking systems, etc), particularly
where an electronic control module is used.
Also refer to the precautions given in Chapter
5, Section 1.
General
1A typical electrical circuit consists of an
electrical component, any switches, relays,
motors, fuses, fusible links or circuit breakers
related to that component, and the wiring and
connectors which link the component to both
the battery and the chassis. To help to
pinpoint a problem in an electrical circuit,
wiring diagrams are included at the end of this
manual.
2Before attempting to diagnose an electrical
fault, first study the appropriate wiring
diagram, to obtain a complete understanding
of the components included in the particular
circuit concerned. The possible sources of a
fault can be narrowed down by noting if other
components related to the circuit are
operating properly. If several components or
circuits fail at one time, the problem is likely to
be related to a shared fuse or earth
connection.
3Electrical problems usually stem from
simple causes, such as loose or corroded
connections, a faulty earth connection, a
blown fuse, a melted fusible link, or a faulty
relay (refer to Section 3 for details of testing
relays). Visually inspect the condition of all
fuses, wires and connections in a problem
circuit before testing the components. Use
the wiring diagrams to determine which
terminal connections will need to be checked
in order to pinpoint the trouble-spot.
4The basic tools required for electrical fault-
finding include a circuit tester or voltmeter (a
12-volt bulb with a set of test leads can alsobe used for certain tests); an ohmmeter (to
measure resistance and check for continuity);
a battery and set of test leads; and a jumper
wire, preferably with a circuit breaker or fuse
incorporated, which can be used to bypass
suspect wires or electrical components.
Before attempting to locate a problem with
test instruments, use the wiring diagram to
determine where to make the connections.
5To find the source of an intermittent wiring
fault (usually due to a poor or dirty
connection, or damaged wiring insulation), a
“wiggle” test can be performed on the wiring.
This involves wiggling the wiring by hand to
see if the fault occurs as the wiring is moved.
It should be possible to narrow down the
source of the fault to a particular section of
wiring. This method of testing can be used in
conjunction with any of the tests described in
the following sub-Sections.
6Apart from problems due to poor
connections, two basic types of fault can
occur in an electrical circuit - open-circuit, or
short-circuit.
7Open-circuit faults are caused by a break
somewhere in the circuit, which prevents
current from flowing. An open-circuit fault will
prevent a component from working.
8Short-circuit faults are caused by a “short”
somewhere in the circuit, which allows the
current flowing in the circuit to “escape” along
an alternative route, usually to earth. Short-
circuit faults are normally caused by a
breakdown in wiring insulation, which allows a
feed wire to touch either another wire, or an
earthed component such as the bodyshell. A
short-circuit fault will normally cause the
relevant circuit fuse to blow.
Finding an open-circuit
9To check for an open-circuit, connect one
lead of a circuit tester or the negative lead of a
voltmeter either to the battery negative
terminal or to a known good earth.
10Connect the other lead to a connector in
the circuit being tested, preferably nearest to
the battery or fuse. At this point, battery
voltage should be present, unless the lead
from the battery or the fuse itself is faulty
(bearing in mind that some circuits are live
only when the ignition switch is moved to a
particular position).
11Switch on the circuit, then connect the
tester lead to the connector nearest the circuit
switch on the component side.
12If voltage is present (indicated either by
the tester bulb lighting or a voltmeter reading,
as applicable), this means that the section of
the circuit between the relevant connector
and the switch is problem-free.
13Continue to check the remainder of the
circuit in the same fashion.
14When a point is reached at which no
voltage is present, the problem must lie
between that point and the previous test point
with voltage. Most problems can be traced to
a broken, corroded or loose connection.
Finding a short-circuit
15To check for a short-circuit, first
disconnect the load(s) from the circuit (loads
are the components which draw current from
a circuit, such as bulbs, motors, heating
elements, etc).
16Remove the relevant fuse from the circuit,
and connect a circuit tester or voltmeter to the
fuse connections.
17Switch on the circuit, bearing in mind that
some circuits are live only when the ignition
switch is moved to a particular position.
18If voltage is present (indicated either by
the tester bulb lighting or a voltmeter reading,
as applicable), this means that there is a
short-circuit.
19If no voltage is present during this test,
but the fuse still blows with the load(s)
reconnected, this indicates an internal fault in
the load(s).
Finding an earth fault
20The battery negative terminal is
connected to “earth” - the metal of the
engine/transmission unit and the vehicle body
- and many systems are wired so that they
only receive a positive feed, the current
returning via the metal of the car body. This
means that the component mounting and the
body form part of that circuit. Loose or
corroded mountings can therefore cause a
range of electrical faults, ranging from total
failure of a circuit, to a puzzling partial failure.
In particular, lights may shine dimly (especially
when another circuit sharing the same earth
point is in operation), motors (eg wiper motors
or the radiator cooling fan motor) may run
slowly, and the operation of one circuit may
have an apparently-unrelated effect on
another. Note that on many vehicles, earth
straps are used between certain components,
such as the engine/transmission and the
body, usually where there is no metal-to-
metal contact between components, due to
flexible rubber mountings, etc.
21To check whether a component is
properly earthed, disconnect the battery (refer
to Chapter 5, Section 1) and connect one lead
of an ohmmeter to a known good earth point.
Connect the other lead to the wire or earth
connection being tested. The resistance
reading should be zero; if not, check the
connection as follows.
22If an earth connection is thought to be
faulty, dismantle the connection, and clean
both the bodyshell and the wire terminal (or
the component earth connection mating
surface) back to bare metal. Be careful to
remove all traces of dirt and corrosion, then
use a knife to trim away any paint, so that a
clean metal-to-metal joint is made. On
reassembly, tighten the joint fasteners
securely; if a wire terminal is being refitted,
use serrated washers between the terminal
and the bodyshell, to ensure a clean and
secure connection. When the connection is
2 Electrical fault finding -
general information
12•4 Body electrical system
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12•28 Wiring diagrams
Diagram 4: Engine management – ignition, tachometer, cooling fan and diagnostic connectors (manual transmission models)
procarmanuals.com

Wiring diagrams 12•31
12
Diagram 7: Engine management – cooling fan, solenoid valve unit and diagnostic connectors (automatic transmission models)
procarmanuals.com

REF•6Fault Finding
Engine 1
m mEngine backfires
m mEngine difficult to start when cold
m mEngine difficult to start when hot
m mEngine fails to rotate when attempting to start
m mEngine hesitates on acceleration
m mEngine idles erratically
m mEngine lacks power
m mEngine misfires at idle speed
m mEngine misfires throughout the driving speed range
m mEngine noises
m mEngine rotates but will not start
m mEngine runs-on after switching off
m mEngine stalls
m mEngine starts but stops immediately
m mOil pressure warning light illuminated with engine running
m mStarter motor noisy or excessively-rough in engagement
Cooling system 2
m
mCorrosion
m mExternal coolant leakage
m mInternal coolant leakage
m mOvercooling
m mOverheating
Fuel and exhaust systems 3
m
mExcessive fuel consumption
m mExcessive noise or fumes from exhaust system
m mFuel leakage and/or fuel odour
Clutch 4
m
mClutch fails to disengage (unable to select gears)
m mClutch slips (engine speed increases with no increase
in vehicle speed)
m mJudder as clutch is engaged
m mNoise when depressing or releasing clutch pedal
m mPedal travels to floor - no pressure or very little resistance
Manual transmission 5
m
mJumps out of gear
m mLubricant leaks
m mNoisy in neutral with engine running
m mNoisy in one particular gear
m mVibration
Automatic transmission 6
m
mEngine will not start in any gear, or starts in gears
other than Park or Neutral
m mFluid leakage
m mGeneral gear selection problems
m mTransmission fluid brown, or has burned smell
m mTransmission slips, shifts roughly, is noisy, or
has no drive in forward or reverse gears
m mTransmission will not downshift (kickdown) with
accelerator fully depressed
Driveshafts 7
m mClicking or knocking noise on turns (at slow speed on full-lock)
m mVibration when accelerating or decelerating
Braking system 8
m
mBrake pedal feels spongy when depressed
m mBrakes binding
m mExcessive brake pedal effort required to stop vehicle
m mExcessive brake pedal travel
m mJudder felt through brake pedal or steering wheel when braking
m mNoise (grinding or high-pitched squeal) when brakes applied
m mRear wheels locking under normal braking
m mVehicle pulls to one side under braking
Suspension and steering systems 9
m
mExcessive pitching and/or rolling around corners, or during
braking
m mExcessive play in steering
m mExcessively-stiff steering
m mLack of power assistance
m mTyre wear excessive
m mVehicle pulls to one side
m mWandering or general instability
m mWheel wobble and vibration
Electrical system 10
m
mBattery will not hold a charge for more than a few days
m mCentral locking system inoperative, or unsatisfactory in operation
m mElectric windows inoperative, or unsatisfactory in operation
m mHorn inoperative, or unsatisfactory in operation
m mIgnition warning light fails to come on
m mIgnition warning light remains illuminated with engine running
m mInstrument readings inaccurate or erratic
m mLights inoperative
m mWindscreen/tailgate washers inoperative, or unsatisfactory in
operation
m mWindscreen/tailgate wipers inoperative, or unsatisfactory in
operation
procarmanuals.com

REF•7
Engine fails to rotate when attempting to start
m mBattery terminal connections loose or corroded (Chapter 5).
m mBattery discharged or faulty (Chapter 5).
m mBroken, loose or disconnected wiring in the starting circuit
(Chapter 5).
m mDefective starter solenoid or switch (Chapter 5).
m mDefective starter motor (Chapter 5).
m mStarter pinion or flywheel ring gear teeth loose or broken (Chap-
ter 5).
m mEngine earth strap broken or disconnected (Chapter 5).
m mAutomatic transmission not in Park/Neutral position, or selector
lever position sensor faulty (Chapter 7, Part B).
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 5).
m mIgnition components damp or damaged (Chapters 1 and 5).
m mBroken, loose or disconnected wiring in the ignition circuit
(Chapters 1 and 5).
m mWorn, faulty or incorrectly-gapped spark plugs (Chapter 1).
m mMajor mechanical failure (eg camshaft drive) (Chapter 2, Part A).
Engine difficult to start when cold
m
mBattery discharged (Chapter 5).
m mBattery terminal connections loose or corroded (Chapter 5).
m mWorn, faulty or incorrectly-gapped spark plugs (Chapter 1).
m mOther ignition system fault (Chapters 1 and 5).
m mEngine management system fault (Chapters 1, 4, 5 and 6)
m mLow cylinder compressions (Chapter 2, Part A).
Engine difficult to start when hot
m
mAir filter element dirty or clogged (Chapter 1).
m mEngine management system fault (Chapters 1, 4, 5 and 6)
m mLow cylinder compressions (Chapter 2, Part A).
m mFaulty hydraulic tappet(s) (Chapter 2, Part A).
Starter motor noisy or excessively-rough in
engagement
m mStarter pinion or flywheel ring gear teeth loose or broken (Chapter 5).
m mStarter motor mounting bolts loose or missing (Chapter 5).
m mStarter motor internal components worn or damaged (Chapter 5).
Engine starts but stops immediately
m
mLoose or faulty electrical connections in the ignition circuit
(Chapters 1 and 5).
m mEngine management system fault (Chapters 1, 4, 5 and 6)
m mVacuum leak at the inlet manifold (Chapters 1, 4 and 6).
Engine idles erratically
m
mIdle speed control valve faulty (Chapter 4).
m mEngine management system fault (Chapters 1, 4, 5 and 6)
m mAir filter element clogged (Chapter 1).
m mVacuum leak at the inlet manifold or associated hoses (Chap-
ters 1, 4 and 6).
m mWorn, faulty or incorrectly-gapped spark plugs (Chapter 1).
m mFaulty hydraulic tappet(s) (Chapter 2, Part A).
m mUneven or low cylinder compressions (Chapter 2, Part A).
m mCamshaft lobes worn (Chapter 2).
m mTiming belt incorrectly-tensioned (Chapter 2, Part A).
Engine misfires at idle speed
m
mWorn, faulty or incorrectly-gapped spark plugs (Chapter 1).
m mFaulty spark plug HT leads (Chapter 1).
m mIdle speed control valve faulty (Chapter 4).
m mIncorrect ignition timing (Chapters 5 and 6).
m mEngine management system fault (Chapters 1, 4, 5 and 6)
m mVacuum leak at the inlet manifold or associated hoses (Chap-
ters 1, 4 and 6).
m mFaulty hydraulic tappet(s) (Chapter 2, Part A).
m mUneven or low cylinder compressions (Chapter 2, Part A).
m mDisconnected, leaking or perished crankcase ventilation hoses
(Chapters 1 and 6).
Fault Finding
The vehicle owner who does his or her own maintenance according
to the recommended service schedules should not have to use this
section of the manual very often. Modern component reliability is such
that, provided those items subject to wear or deterioration are inspected
or renewed at the specified intervals, sudden failure is comparatively
rare. Faults do not usually just happen as a result of sudden failure, but
develop over a period of time. Major mechanical failures in particular are
usually preceded by characteristic symptoms over hundreds or even
thousands of miles. Those components which do occasionally fail
without warning are often small and easily carried in the vehicle.
With any fault-finding, the first step is to decide where to begin
investigations. Sometimes this is obvious, but on other occasions, a
little detective work will be necessary. The owner who makes half a
dozen haphazard adjustments or replacements may be successful in
curing a fault (or its symptoms), but will be none the wiser if the fault
recurs, and ultimately may have spent more time and money than was
necessary. A calm and logical approach will be found to be more
satisfactory in the long run. Always take into account any warning
signs or abnormalities that may have been noticed in the period
preceding the fault - power loss, high or low gauge readings, unusual
smells, etc - and remember that failure of components such as fuses
or spark plugs may only be pointers to some underlying fault.
The pages which follow provide an easy reference guide to the
more common problems which may occur during the operation of the
vehicle. These problems and their possible causes are grouped underheadings denoting various components or systems, such as Engine,
Cooling system, etc. The Chapter and/or Section which deals with the
problem is also shown in brackets. Whatever the fault, certain basic
principles apply. These are as follows:
Verify the fault. This is simply a matter of being sure that you know
what the symptoms are before starting work. This is particularly
important if you are investigating a fault for someone else, who may
not have described it very accurately.
Don’t overlook the obvious. For example, if the vehicle won’t start, is
there petrol in the tank? (Don’t take anyone else’s word on this
particular point, and don’t trust the fuel gauge either!) If an electrical
fault is indicated, look for loose or broken wires before digging out the
test gear.
Cure the disease, not the symptom. Substituting a flat battery with a
fully-charged one will get you off the hard shoulder, but if the underlying
cause is not attended to, the new battery will go the same way. Similarly,
changing oil-fouled spark plugs for a new set will get you moving again,
but remember that the reason for the fouling (if it wasn’t simply an
incorrect grade of plug) will have to be established and corrected.
Don’t take anything for granted. Particularly, don’t forget that a
“new” component may itself be defective (especially if it’s been
rattling around in the boot for months), and don’t leave components
out of a fault diagnosis sequence just because they are new or
recently fitted. When you do finally diagnose a difficult fault, you’ll
probably realise that all the evidence was there from the start.
1 Engine
Introduction
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Engine misfires throughout the driving speed range
m mFuel filter choked (Chapter 1).
m mFuel pump faulty or delivery pressure low (Chapter 4).
m mFuel tank vent blocked or fuel pipes restricted (Chapter 4).
m mVacuum leak at the inlet manifold or associated hoses (Chap-
ters 1, 4 and 6).
m mWorn, faulty or incorrectly-gapped spark plugs (Chapter 1).
m mFaulty spark plug HT leads (Chapter 1).
m mFaulty ignition coil (Chapter 5).
m mEngine management system fault (Chapters 1, 4, 5 and 6)
m mUneven or low cylinder compressions (Chapter 2, Part A).
Engine hesitates on acceleration
m
mWorn, faulty or incorrectly-gapped spark plugs (Chapter 1).
m mEngine management system fault (Chapters 1, 4, 5 and 6).
m mVacuum leak at the inlet manifold or associated hoses (Chap-
ters 1, 4 and 6).
Engine stalls
m mIdle speed control valve faulty (Chapter 4).
m mEngine management system fault (Chapters 1, 4, 5 and 6).
m mVacuum leak at the inlet manifold or associated hoses (Chap-
ters 1, 4 and 6).
m mFuel filter choked (Chapter 1).
m mFuel pump faulty or delivery pressure low (Chapter 4).
m mFuel tank vent blocked or fuel pipes restricted (Chapter 4).
Engine lacks power
m
mIncorrect ignition timing (Chapters 5 and 6).
m mEngine management system fault (Chapters 1, 4, 5 and 6).
m mTiming belt incorrectly fitted or incorrectly tensioned (Chapter 2,
Part A).
m mFuel filter choked (Chapter 1).
m mFuel pump faulty or delivery pressure low (Chapter 4).
m mUneven or low cylinder compressions (Chapter 2, Part A).
m mWorn, faulty or incorrectly-gapped spark plugs (Chapter 1).
m mVacuum leak at the inlet manifold or associated hoses (Chap-
ters 1, 4 and 6).
m mBrakes binding (Chapters 1 and 9).
m mClutch slipping (Chapter 8).
m mAutomatic transmission fluid level incorrect (Chapter 1).
Engine runs-on after switching off
m
mIdle speed excessively high (Chapters 4 and 6).
m mEngine management system fault (Chapters 1, 4, 5 and 6).
m mExcessive carbon build-up in engine (Chapter 2, Part A).
m mHigh engine operating temperature (Chapter 3).
Engine backfires
m
mIgnition timing incorrect (Chapters 5 and 6).
m mEngine management system fault (Chapters 1, 4, 5 and 6).
m mTiming belt incorrectly fitted or incorrectly tensioned (Chapter 2,
Part A).
m mVacuum leak at the inlet manifold or associated hoses (Chap-
ters 1, 4 and 6).
Oil pressure warning light illuminated with engine
running
m mLow oil level or incorrect oil grade (Chapter 1).
m mFaulty oil pressure warning light switch (Chapter 2, Part A).
m mWorn engine bearings and/or oil pump (Chapter 2).
m mHigh engine operating temperature (Chapter 3).
m mOil pressure relief valve defective (Chapter 2, Part A).
m mOil pick-up strainer clogged (Chapter 2, Part A).
Engine noises
Pre-ignition (pinking) or knocking during acceleration or under
load
m mIgnition timing incorrect (Chapters 5 and 6).
m mIncorrect grade of fuel (Chapter 4).
m mVacuum leak at the inlet manifold or associated hoses (Chap-
ters 1, 4 and 6).
m mExcessive carbon build-up in engine (Chapter 2, Part A).
Whistling or wheezing noises
m mLeaking inlet manifold gasket (Chapter 2, Part A).
m mLeaking exhaust manifold gasket or downpipe-to-manifold joint
(Chapters 1, 2 Part A, and 4).
m mLeaking vacuum hose (Chapters 1, 4, 6 and 9).
m mBlowing cylinder head gasket (Chapter 2, Part A).
Tapping or rattling noises
m mFaulty hydraulic tappet(s) (Chapter 2, Part A).
m mWorn valve gear or camshaft (Chapter 2, Part A).
m mWorn timing belt or tensioner (Chapter 2, Part A).
m mAncillary component fault (water pump, alternator, etc) (Chap-
ters 3 and 5).
Knocking or thumping noises
m mWorn big-end bearings (regular heavy knocking, perhaps less
under load) (Chapter 2, Part B).
m mWorn main bearings (rumbling and knocking, perhaps worsening
under load) (Chapter 2, Part B).
m mPiston slap (most noticeable when cold) (Chapter 2, Part B).
m mAncillary component fault (water pump, alternator, etc) (Chap-
ters 3 and 5).
REF•8Fault Finding
2 Cooling system
Overheating
m mInsufficient coolant in system (Chapter 1).
m mThermostat faulty (Chapter 3).
m mRadiator core blocked or grille restricted (Chapter 3).
m mRadiator electric cooling fan(s) or coolant temperature sensor faulty
(Chapter 3).
m mEngine management system fault (Chapters 1, 4, 5 and 6).
m mPressure cap faulty (Chapter 3).
m mAuxiliary drivebelt worn or slipping (Chapter 1).
m mIgnition timing incorrect (Chapters 5 and 6).
m mInaccurate coolant temperature gauge sender (Chapter 3).
m mAir-lock in cooling system (Chapter 1).
Overcooling
m
mThermostat faulty (Chapter 3).
m mInaccurate coolant temperature gauge sender (Chapter 3).
External coolant leakage
m
mDeteriorated or damaged hoses or hose clips (Chapter 1).
m mRadiator core or heater matrix leaking (Chapter 3).
m mPressure cap faulty (Chapter 3).
m mWater pump seal leaking (Chapter 3).
m mBoiling due to overheating (Chapter 3).
m mCore plug leaking (Chapter 2, Part B).
procarmanuals.com

REF•13Glossary of Technical Terms
A
ABS (Anti-lock brake system)A system,
usually electronically controlled, that senses
incipient wheel lockup during braking and
relieves hydraulic pressure at wheels that are
about to skid.
Air bag An inflatable bag hidden in the
steering wheel (driver’s side) or the dash or
glovebox (passenger side). In a head-on
collision, the bags inflate, preventing the
driver and front passenger from being thrown
forward into the steering wheel or windscreen.
Air cleanerA metal or plastic housing,
containing a filter element, which removes
dust and dirt from the air being drawn into the
engine.
Air filter elementThe actual filter in an air
cleaner system, usually manufactured from
pleated paper and requiring renewal at regular
intervals.
Allen keyA hexagonal wrench which fits into
a recessed hexagonal hole.
Alligator clipA long-nosed spring-loaded
metal clip with meshing teeth. Used to make
temporary electrical connections.
AlternatorA component in the electrical
system which converts mechanical energy
from a drivebelt into electrical energy to
charge the battery and to operate the starting
system, ignition system and electrical
accessories.
Ampere (amp)A unit of measurement for the
flow of electric current. One amp is the
amount of current produced by one volt
acting through a resistance of one ohm.
Anaerobic sealerA substance used to
prevent bolts and screws from loosening.
Anaerobic means that it does not require
oxygen for activation. The Loctite brand is
widely used.
AntifreezeA substance (usually ethylene
glycol) mixed with water, and added to a
vehicle’s cooling system, to prevent freezing
of the coolant in winter. Antifreeze also
contains chemicals to inhibit corrosion and
the formation of rust and other deposits that
would tend to clog the radiator and coolant
passages and reduce cooling efficiency.
Anti-seize compoundA coating that
reduces the risk of seizing on fasteners that
are subjected to high temperatures, such as
exhaust manifold bolts and nuts.
AsbestosA natural fibrous mineral with great
heat resistance, commonly used in the
composition of brake friction materials.Asbestos is a health hazard and the dust
created by brake systems should never be
inhaled or ingested.
AxleA shaft on which a wheel revolves, or
which revolves with a wheel. Also, a solid
beam that connects the two wheels at one
end of the vehicle. An axle which also
transmits power to the wheels is known as a
live axle.
AxleshaftA single rotating shaft, on either
side of the differential, which delivers power
from the final drive assembly to the drive
wheels. Also called a driveshaft or a halfshaft.
BBall bearingAn anti-friction bearing
consisting of a hardened inner and outer race
with hardened steel balls between two races.
BearingThe curved surface on a shaft or in a
bore, or the part assembled into either, that
permits relative motion between them with
minimum wear and friction.
Big-end bearingThe bearing in the end of
the connecting rod that’s attached to the
crankshaft.
Bleed nippleA valve on a brake wheel
cylinder, caliper or other hydraulic component
that is opened to purge the hydraulic system
of air. Also called a bleed screw.
Brake bleedingProcedure for removing air
from lines of a hydraulic brake system.
Brake discThe component of a disc brake
that rotates with the wheels.Brake drumThe component of a drum brake
that rotates with the wheels.
Brake liningsThe friction material which
contacts the brake disc or drum to retard the
vehicle’s speed. The linings are bonded or
riveted to the brake pads or shoes.
Brake padsThe replaceable friction pads
that pinch the brake disc when the brakes are
applied. Brake pads consist of a friction
material bonded or riveted to a rigid backing
plate.
Brake shoeThe crescent-shaped carrier to
which the brake linings are mounted and
which forces the lining against the rotating
drum during braking.
Braking systemsFor more information on
braking systems, consult the Haynes
Automotive Brake Manual.
Breaker barA long socket wrench handle
providing greater leverage.
BulkheadThe insulated partition between
the engine and the passenger compartment.
CCaliperThe non-rotating part of a disc-brake
assembly that straddles the disc and carries
the brake pads. The caliper also contains the
hydraulic components that cause the pads to
pinch the disc when the brakes are applied. A
caliper is also a measuring tool that can be set
to measure inside or outside dimensions of an
object.
CamshaftA rotating shaft on which a series
of cam lobes operate the valve mechanisms.
The camshaft may be driven by gears, by
sprockets and chain or by sprockets and a
belt.
CanisterA container in an evaporative
emission control system; contains activated
charcoal granules to trap vapours from the
fuel system.
CarburettorA device which mixes fuel with
air in the proper proportions to provide a
desired power output from a spark ignition
internal combustion engine.
CastellatedResembling the parapets along
the top of a castle wall. For example, a
castellated balljoint stud nut.
CastorIn wheel alignment, the backward or
forward tilt of the steering axis. Castor is
positive when the steering axis is inclined
rearward at the top.
Canister
Brake bleeding
Bearing
Air filter
procarmanuals.com

REF•15Glossary 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
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