1993 FORD SIERRA belt

Buying spare parts
Spare parts are available from many
sources, including maker’s appointed
garages, accessory shops, and motor factors.
To be sure of obtaining the correct parts, it
will sometimes be necessary to quote the
vehicle identification number. If possible, it
can also be useful to take the old parts along
for positive identification. Items such as
starter motors and alternators may be
available under a service exchange scheme -
any parts returned should always be clean.
Our advice regarding spare part sources is
as follows.
Officially-appointed garages
This is the best source of parts which are
peculiar to your car, and which are not
otherwise generally available (eg badges,
interior trim, certain body panels, etc). It is
also the only place at which you should buy
parts if the vehicle is still under warranty.
Accessory shops
These are very good places to buy
materials and components needed for themaintenance of your car (oil, air and fuel
filters, spark plugs, light bulbs, drivebelts, oils
and greases, brake pads, touch-up paint, etc).
Components of this nature sold by a
reputable shop are of the same standard as
those used by the car manufacturer.
Besides components, these shops also sell
tools and general accessories, usually have
convenient opening hours, charge lower
prices, and can often be found not far from
home. Some accessory shops have parts
counters where the components needed for
almost any repair job can be purchased or
ordered.
Motor factors
Good factors will stock all the more
important components which wear out
comparatively quickly, and can sometimes
supply individual components needed for the
overhaul of a larger assembly (eg brake seals
and hydraulic parts, bearing shells, pistons,
valves, alternator brushes). They may also
handle work such as cylinder block reboring,
crankshaft regrinding and balancing, etc.
Tyre and exhaust specialists
These outlets may be independent, or
members of a local or national chain. They
frequently offer competitive prices when
compared with a main dealer or local garage,
but it will pay to obtain several quotes before
making a decision. When researching prices,
also ask what “extras” may be added - for
instance, fitting a new valve and balancing the
wheel are both commonly charged on top of
the price of a new tyre.
Other sources
Beware of parts or materials obtained from
market stalls, car boot sales or similar outlets.
Such items are not invariably sub-standard,
but there is little chance of compensation if
they do prove unsatisfactory. In the case of
safety-critical components such as brake
pads, there is the risk not only of financial loss
but also of an accident causing injury or death.
Second-hand components or assemblies
obtained from a car breaker can be a good
buy in some circumstances, but this sort of
purchase is best made by the experienced
DIY mechanic.
Vehicle identification numbers
Modifications are a continuing and
unpublicised process in vehicle manufacture,
quite apart from major model changes. Spareparts lists are compiled upon a numerical
basis, the individual vehicle identification
numbers being essential to correct
identification of the component concerned.
When ordering spare parts, always give as
much information as possible. Quote the car
model, year of manufacture, body and engine
numbers, as appropriate.
The Vehicle Identification Number (VIN)
plate is mounted on the right-hand side of the
body front panel, and may be seen once the
bonnet is open (see illustration).Besides the
VIN it also carries information on vehicle
equipment and permissible loads.
The engine numberis situated on the
cylinder block. On SOHC engines, the number
is located on the right-hand side of thecylinder block in front of the engine mounting
bracket. On 1.8 litre (R2A) CVH engines, the
number is located on the front upper
right-hand side of the cylinder block. On 1.6
and 1.8 litre (R6A) CVH engines, the engine
number is stamped on the front lower face of
the cylinder block, on the alternator side of
the timing cover. On DOHC engines, the
engine number is stamped on the front face of
the cylinder block, below the upper timing
chain cover (see illustrations)..
Other identification numbers or codes are
stamped on major items such as the gearbox,
final drive housing, distributor etc. These
numbers are unlikely to be needed by the
home mechanic.
Buying spare parts REF•3
Engine code (A) and engine number (B)
locations - SOHC engines
Engine number location -
1.8 litre (R2A) CVH engineEngine number code sticker and engine
number location (A) - DOHC engineEngine number location -
1.6 litre CVH engine
A Engine code B Engine number
REF
Vehicle identification numbers

REF•8MOTtest checks
Seat belts and seats
Note: The following checks are applicable to
all seat belts, front and rear.
MExamine the webbing of all the belts
(including rear belts if fitted) for cuts, serious
fraying or deterioration. Fasten and unfasten
each belt to check the buckles. If applicable,
check the retracting mechanism. Check the
security of all seat belt mountings accessible
from inside the vehicle.
MThe front seats themselves must be
securely attached and the backrests must
lock in the upright position.
Doors
MBoth front doors must be able to be opened
and closed from outside and inside, and must
latch securely when closed.
Vehicle identification
MNumber plates must be in good condition,
secure and legible, with letters and numbers
correctly spaced – spacing at (A) should be
twice that at (B).
MThe VIN plate (A) and homologation plate
(B) must be legible.
Electrical equipment
MSwitch on the ignition and check the
operation of the horn.
MCheck the windscreen washers and wipers,
examining the wiper blades; renew damaged
or perished blades. Also check the operation
of the stop-lights.
MCheck the operation of the sidelights and
number plate lights. The lenses and reflectors
must be secure, clean and undamaged.
MCheck the operation and alignment of the
headlights. The headlight reflectors must not
be tarnished and the lenses must be
undamaged.
MSwitch on the ignition and check the
operation of the direction indicators (including
the instrument panel tell-tale) and the hazard
warning lights. Operation of the sidelights and
stop-lights must not affect the indicators - if it
does, the cause is usually a bad earth at the
rear light cluster.
MCheck the operation of the rear foglight(s),
including the warning light on the instrument
panel or in the switch.
Footbrake
MExamine the master cylinder, brake pipes
and servo unit for leaks, loose mountings,
corrosion or other damage.
MThe fluid reservoir must be secure and the
fluid level must be between the upper (A) and
lower (B) markings.MInspect both front brake flexible hoses for
cracks or deterioration of the rubber. Turn the
steering from lock to lock, and ensure that the
hoses do not contact the wheel, tyre, or any
part of the steering or suspension mechanism.
With the brake pedal firmly depressed, check
the hoses for bulges or leaks under pressure.
Steering and suspension
MHave your assistant turn the steering wheel
from side to side slightly, up to the point where
the steering gear just begins to transmit this
movement to the roadwheels. Check for
excessive free play between the steering
wheel and the steering gear, indicating wear or
insecurity of the steering column joints, the
column-to-steering gear coupling, or the
steering gear itself.
MHave your assistant turn the steering wheel
more vigorously in each direction, so that the
roadwheels just begin to turn. As this is done,
examine all the steering joints, linkages,
fittings and attachments. Renew any
component that shows signs of wear or
damage. On vehicles with power steering,
check the security and condition of the
steering pump, drivebelt and hoses.
MCheck that the vehicle is standing level,
and at approximately the correct ride height.
Shock absorbers
MDepress each corner of the vehicle in turn,
then release it. The vehicle should rise and
then settle in its normal position. If the vehicle
continues to rise and fall, the shock absorber
is defective. A shock absorber which has
seized will also cause the vehicle to fail.
2Checks carried out
WITH THE VEHICLE ON THE
GROUND

REF•10MOTtest checks
MExamine the handbrake mechanism,
checking for frayed or broken cables,
excessive corrosion, or wear or insecurity of
the linkage. Check that the mechanism works
on each relevant wheel, and releases fully,
without binding.
MIt is not possible to test brake efficiency
without special equipment, but a road test
can be carried out later to check that the
vehicle pulls up in a straight line.
Fuel and exhaust systems
MInspect the fuel tank (including the filler
cap), fuel pipes, hoses and unions. All
components must be secure and free from
leaks.
MExamine the exhaust system over its entire
length, checking for any damaged, broken or
missing mountings, security of the retaining
clamps and rust or corrosion.
Wheels and tyres
MExamine the sidewalls and tread area of
each tyre in turn. Check for cuts, tears, lumps,
bulges, separation of the tread, and exposure
of the ply or cord due to wear or damage.
Check that the tyre bead is correctly seated
on the wheel rim, that the valve is sound andproperly seated, and that the wheel is not
distorted or damaged.
MCheck that the tyres are of the correct size
for the vehicle, that they are of the same size
and type on each axle, and that the pressures
are correct.
MCheck the tyre tread depth. The legal
minimum at the time of writing is 1.6 mm over
at least three-quarters of the tread width.
Abnormal tread wear may indicate incorrect
front wheel alignment.
Body corrosion
MCheck the condition of the entire vehicle
structure for signs of corrosion in load-
bearing areas. (These include chassis box
sections, side sills, cross-members, pillars,
and all suspension, steering, braking system
and seat belt mountings and anchorages.)
Any corrosion which has seriously reduced
the thickness of a load-bearing area is likely to
cause the vehicle to fail. In this case
professional repairs are likely to be needed.
MDamage or corrosion which causes sharp
or otherwise dangerous edges to be exposed
will also cause the vehicle to fail.
Petrol models
MHave the engine at normal operating
temperature, and make sure that it is in good
tune (ignition system in good order, air filter
element clean, etc).
MBefore any measurements are carried out,
raise the engine speed to around 2500 rpm,
and hold it at this speed for 20 seconds. Allow
the engine speed to return to idle, and watchfor smoke emissions from the exhaust
tailpipe. If the idle speed is obviously much
too high, or if dense blue or clearly-visible
black smoke comes from the tailpipe for more
than 5 seconds, the vehicle will fail. As a rule
of thumb, blue smoke signifies oil being burnt
(engine wear) while black smoke signifies
unburnt fuel (dirty air cleaner element, or other
carburettor or fuel system fault).
MAn exhaust gas analyser capable of
measuring carbon monoxide (CO) and
hydrocarbons (HC) is now needed. If such an
instrument cannot be hired or borrowed, a
local garage may agree to perform the check
for a small fee.
CO emissions (mixture)
MAt the time of writing, the maximum CO
level at idle is 3.5% for vehicles first used after
August 1986 and 4.5% for older vehicles.
From January 1996 a much tighter limit
(around 0.5%) applies to catalyst-equipped
vehicles first used from August 1992. If the
CO level cannot be reduced far enough to
pass the test (and the fuel and ignition
systems are otherwise in good condition) then
the carburettor is badly worn, or there is some
problem in the fuel injection system or
catalytic converter (as applicable).
HC emissionsMWith the CO emissions within limits, HC
emissions must be no more than 1200 ppm
(parts per million). If the vehicle fails this test
at idle, it can be re-tested at around 2000
rpm; if the HC level is then 1200 ppm or less,
this counts as a pass.
MExcessive HC emissions can be caused by
oil being burnt, but they are more likely to be
due to unburnt fuel.
Diesel models
MThe only emission test applicable to Diesel
engines is the measuring of exhaust smoke
density. The test involves accelerating the
engine several times to its maximum
unloaded speed.
Note: It is of the utmost importance that the
engine timing belt is in good condition before
the test is carried out.
M
Excessive smoke can be caused by a dirty
air cleaner element. Otherwise, professional
advice may be needed to find the cause.
4Checks carried out on
YOUR VEHICLE’S EXHAUST
EMISSION SYSTEM

MFuel filter choked (Chapter 1).
MFuel pump faulty, or delivery pressure low (Chapter 4).
MFuel tank vent blocked, or fuel pipes restricted (Chapter 4).
MFuel injection system fault (Chapter 4).
Engine lacks power
MFuel filter choked (Chapter 1).
MFuel pump faulty, or delivery pressure low (Chapter 4).
MUneven or low cylinder compressions (Chapter 2).
MWorn, faulty or incorrectly-gapped spark plugs (Chapter 1).
MVacuum leak at the throttle body, inlet manifold or associated
hoses (Chapter 4).
MFuel injection system fault (Chapter 4).
MBrakes binding (Chapters 1 and 10).
MClutch slipping (Chapter 6).
Engine backfires
MVacuum leak at the throttle body, inlet manifold or associated
hoses (Chapter 4).
MFuel injection system fault (Chapter 4).
Oil pressure warning light illuminated with engine
running
MLow oil level, or incorrect oil grade (Chapter 1).
MFaulty oil pressure sensor (Chapter 2).
MWorn engine bearings and/or oil pump (Chapter 2).
MExcessively high engine operating temperature (Chapter 3).
MOil pressure relief valve defective (Chapter 2).
MOil pick-up strainer clogged (Chapter 2).
Note:Low oil pressure in a high-mileage engine at tickover is not
necessarily a cause for concern. Sudden pressure loss at speed is far
more significant. In any event, check the gauge or warning light sender
before condemning the engine.
Engine runs-on after switching off
MExcessive carbon build-up in engine (Chapter 2).
MExcessively high engine operating temperature (Chapter 3).
Engine noises
Pre-ignition (pinking) or knocking during acceleration or
under load
MIgnition timing incorrect/ignition system fault (Chapters 1 and 5).
MIncorrect grade of spark plug (Chapter 1).
MIncorrect grade of fuel (Chapter 1).
MVacuum leak at throttle body, inlet manifold or associated hoses
(Chapter 4).
MExcessive carbon build-up in engine (Chapter 2).
MFuel injection system fault (Chapter 4).
Whistling or wheezing noises
MLeaking inlet manifold or throttle body gasket (Chapter 4).
MLeaking exhaust manifold gasket (Chapter 4).
MLeaking vacuum hose (Chapters 4 and 10).
MBlowing cylinder head gasket (Chapter 2).
Tapping or rattling noises
MWorn valve gear, timing chain, camshaft or hydraulic tappets
(Chapter 2).
MAncillary component fault (water pump, alternator, etc) (Chapters 3, 5)
Knocking or thumping noises
MWorn big-end bearings (regular heavy knocking, perhaps less
under load) (Chapter 2).
MWorn main bearings (rumbling and knocking, perhaps worsening
under load) (Chapter 2).
MPiston slap (most noticeable when cold) (Chapter 2).
MAncillary component fault (water pump, alternator, etc) (Chapters 3, 5)
Overheating
MAuxiliary drivebelt broken or incorrectly adjusted (Chapter 1).
MInsufficient coolant in system (Chapter 1).
MThermostat faulty (Chapter 3).
MRadiator core blocked, or grille restricted (Chapter 3).
MElectric cooling fan or thermostatic switch faulty (Chapter 3).
MViscous-coupled fan faulty (Chapter 3).
MIgnition timing incorrect, or ignition system fault (Chapters 1 and 5).
MInaccurate temperature gauge sender unit (Chapter 3).
MAirlock in cooling system (Chapter 3).
Overcooling
MThermostat faulty (Chapter 3).
MInaccurate temperature gauge sender unit (Chapter 3).
External coolant leakage
MDeteriorated or damaged hoses or hose clips (Chapter 1).
MRadiator core or heater matrix leaking (Chapter 3).
MPressure cap faulty (Chapter 3).
MWater pump internal seal leaking (Chapter 3).
MWater pump-to-block seal leaking (Chapter 3).
MBoiling due to overheating (Chapter 3).
MCore plug leaking (Chapter 2).
Internal coolant leakage
MLeaking cylinder head gasket (Chapter 2).
MCracked cylinder head or cylinder block (Chapter 2).
Corrosion
MInfrequent draining and flushing (Chapter 1).
MIncorrect coolant mixture or inappropriate coolant type (Chapter 1).
Fault diagnosisREF•13
REF
Cooling system
Excessive fuel consumption
MAir filter element dirty or clogged (Chapter 1).
MFuel injection system fault (Chapter 4).
MIgnition timing incorrect or ignition system fault (Chapters 1 and 5).
MBrakes binding (Chapter 10).
MTyres under-inflated (Chapter 1).
Fuel leakage and/or fuel odour
MDamaged fuel tank, pipes or connections (Chapters 1 and 4).
Excessive noise or fumes from exhaust system
MLeaking exhaust system or manifold joints (Chapters 1 and 4).
MLeaking, corroded or damaged silencers or pipe (Chapters 1 and 4).
MBroken mountings causing body or suspension contact (Chapter 4).
Fuel and exhaust systems

Brakes binding
MSeized brake caliper piston(s) (Chapter 10).
MIncorrectly-adjusted handbrake mechanism (Chapter 10).
MFaulty master cylinder (Chapter 10).
Rear wheels locking under normal braking
MSeized brake caliper piston(s) (Chapter 10).
MFaulty brake pressure regulator (Chapter 10).
Note:For problems associated with the starting system, refer to the
faults listed under “Engine” earlier in this Section.
Battery will not hold a charge for more than a few
days
MBattery defective internally (Chapter 5).
MBattery electrolyte level low - where applicable (Chapter 1).
MBattery terminal connections loose or corroded (Chapter 1).
MAuxiliary drivebelt worn - or incorrectly adjusted (Chapter 1).
MAlternator not charging at correct output (Chapter 5).MAlternator or voltage regulator faulty (Chapter 5).
MShort-circuit causing continual battery drain (Chapters 5 and 13).
Ignition/no-charge warning light remains illuminated
with engine running
MAuxiliary drivebelt broken, worn, or incorrectly adjusted (Chapter 1).
MAlternator brushes worn, sticking, or dirty (Chapter 5).
MAlternator brush springs weak or broken (Chapter 5).
MInternal fault in alternator or voltage regulator (Chapter 5).
MBroken, disconnected, or loose wiring in charging circuit (Chapter 5). Note:Before diagnosing suspension or steering faults, be sure that the
trouble is not due to incorrect tyre pressures, mixtures of tyre types, or
binding brakes.
Vehicle pulls to one side
MDefective tyre (Chapter 1).
MExcessive wear in suspension or steering components (Chapters 1
and 11).
MIncorrect front wheel alignment (Chapter 11).
MAccident damage to steering or suspension components (Chapters 1
and 11).
Wheel wobble and vibration
MFront roadwheels out of balance (vibration felt mainly through the
steering wheel) (Chapter 11).
MRear roadwheels out of balance (vibration felt throughout the
vehicle) (Chapter 11).
MRoadwheels damaged or distorted (Chapter 11).
MFaulty or damaged tyre (Chapter 1).
MWorn steering or suspension joints, bushes or components
(Chapters 1 and 11).
MWheel bolts loose (Chapter 11).
Excessive pitching and/or rolling around corners, or
during braking
MDefective shock absorbers (Chapters 1 and 11).
MBroken or weak coil spring and/or suspension component
(Chapters 1 and 11).
MWorn or damaged anti-roll bar or mountings (Chapter 11).
Wandering or general instability
MIncorrect front wheel alignment (Chapter 11).
MWorn steering or suspension joints, bushes or components
(Chapters 1 and 11).
MRoadwheels out of balance (Chapter 11).
MFaulty or damaged tyre (Chapter 1).
MWheel bolts loose (Chapter 11).
MDefective shock absorbers (Chapters 1 and 11).
Excessively-stiff steering
MLack of steering gear lubricant (Chapter 11).
MSeized track rod end balljoint or suspension balljoint (Chapters 1
and 11).MBroken or incorrectly adjusted auxiliary drivebelt (Chapter 1).
MIncorrect front wheel alignment (Chapter 11).
MSteering rack or column bent or damaged (Chapter 11).
Excessive play in steering
MWorn steering column universal joint(s) (Chapter 11).
MWorn steering track rod end balljoints (Chapters 1 and 11).
MWorn rack-and-pinion steering gear (Chapter 11).
MWorn steering or suspension joints, bushes or components
(Chapters 1 and 11).
Lack of power assistance
MBroken or incorrectly-adjusted auxiliary drivebelt (Chapter 1).
MIncorrect power steering fluid level (Chapter 1).
MRestriction in power steering fluid hoses (Chapter 11).
MFaulty power steering pump (Chapter 11).
MFaulty rack-and-pinion steering gear (Chapter 11).
Tyre wear excessive
Tyres worn on inside or outside edges
MTyres under-inflated (wear on both edges) (Chapter 1).
MIncorrect camber or castor angles (wear on one edge only)
(Chapter 11).
MWorn steering or suspension joints, bushes or components
(Chapters 1 and 11).
MExcessively-hard cornering.
MAccident damage.
Tyre treads exhibit feathered edges
MIncorrect toe setting (Chapter 11).
Tyres worn in centre of tread
MTyres over-inflated (Chapter 1).
Tyres worn on inside and outside edges
MTyres under-inflated (Chapter 1).
MWorn shock absorbers (Chapters 1 and 11).
Tyres worn unevenly
MTyres out of balance (Chapter 1).
MExcessive wheel or tyre run-out (Chapter 1).
MWorn shock absorbers (Chapters 1 and 11).
MFaulty tyre (Chapter 1).
REF•16Fault diagnosis
Steering and suspension
Electrical system

REF•18Glossary 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 thatwould 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.
Brake bleeding
Bearing
Axle assembly
Anti-seize compound
Alternator (exploded view)
Air filter

Glossary of Technical termsREF•19
REF
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.Catalytic converterA silencer-like device in
the exhaust system which converts certain
pollutants in the exhaust gases into less
harmful substances.
CirclipA ring-shaped clip used to prevent
endwise movement of cylindrical parts and
shafts. An internal circlip is installed in a
groove in a housing; an external circlip fits into
a groove on the outside of a cylindrical piece
such as a shaft.
ClearanceThe amount of space between
two parts. For example, between a piston and
a cylinder, between a bearing and a journal,
etc.
Coil springA spiral of elastic steel found in
various sizes throughout a vehicle, for
example as a springing medium in the
suspension and in the valve train.
CompressionReduction in volume, and
increase in pressure and temperature, of a
gas, caused by squeezing it into a smaller
space.
Compression ratioThe relationship between
cylinder volume when the piston is at top
dead centre and cylinder volume when the
piston is at bottom dead centre.
Constant velocity (CV) jointA type of
universal joint that cancels out vibrations
caused by driving power being transmitted
through an angle.
Core plugA disc or cup-shaped metal device
inserted in a hole in a casting through which
core was removed when the casting was
formed. Also known as a freeze plug or
expansion plug.
CrankcaseThe lower part of the engine
block in which the crankshaft rotates.
CrankshaftThe main rotating member, or
shaft, running the length of the crankcase,
with offset “throws” to which the connecting
rods are attached.Crocodile clipSee Alligator clip
DDiagnostic codeCode numbers obtained by
accessing the diagnostic mode of an engine
management computer. This code can be
used to determine the area in the system
where a malfunction may be located.
Disc brakeA brake design incorporating a
rotating disc onto which brake pads are
squeezed. The resulting friction converts the
energy of a moving vehicle into heat.
Double-overhead cam (DOHC)An engine
that uses two overhead camshafts, usually
one for the intake valves and one for the
exhaust valves.
Drivebelt(s)The belt(s) used to drive
accessories such as the alternator, water
pump, power steering pump, air conditioning
compressor, etc. off the crankshaft pulley.
DriveshaftAny shaft used to transmit
motion. Commonly used when referring to the
axleshafts on a front wheel drive vehicle.
Drum brakeA type of brake using a drum-
shaped metal cylinder attached to the inner
surface of the wheel. When the brake pedal is
pressed, curved brake shoes with friction
linings press against the inside of the drum to
slow or stop the vehicle.
Castellated nut
Catalytic converter
Crankshaft assembly
Carburettor
Canister
Drum brake assembly
Accessory drivebelts
Driveshaft

Glossary of Technical termsREF•21
REF
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 tothe 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.
RotorIn a distributor, the rotating device
inside the cap that connects the centre
electrode and the outer terminals as it turns,
distributing the high voltage from the coil
secondary winding to the proper spark plug.
Also, that part of an alternator which rotates
inside the stator. Also, the rotating assembly
of a turbocharger, including the compressor
wheel, shaft and turbine wheel.
RunoutThe amount of wobble (in-and-out
movement) of a gear or wheel as it’s rotated.
The amount a shaft rotates “out-of-true.” The
out-of-round condition of a rotating part.
SSealantA liquid or paste used to prevent
leakage at a joint. Sometimes used in
conjunction with a gasket.
Sealed beam lampAn older headlight design
which integrates the reflector, lens and
filaments into a hermetically-sealed one-piece
unit. When a filament burns out or the lens
cracks, the entire unit is simply replaced.
Serpentine drivebeltA single, long, wide
accessory drivebelt that’s used on some
newer vehicles to drive all the accessories,
instead of a series of smaller, shorter belts.
Serpentine drivebelts are usually tensioned by
an automatic tensioner.
ShimThin spacer, commonly used to adjust
the clearance or relative positions between
two parts. For example, shims inserted into or
under bucket tappets control valve
clearances. Clearance is adjusted by
changing the thickness of the shim.
Slide hammerA special puller that screws
into or hooks onto a component such as a
shaft or bearing; a heavy sliding handle on the
shaft bottoms against the end of the shaft to
knock the component free.
SprocketA tooth or projection on the
periphery of a wheel, shaped to engage with a
chain or drivebelt. Commonly used to refer to
the sprocket wheel itself.
Starter inhibitor switchOn vehicles with an
O-ring
Serpentine drivebelt
Plastigage