1991 BMW 3 SERIES Disc brake

13 Headlights- adjustment
2
Note:The headlights must be aimed correctly.
If adjusted incorrectly, they could momentarily
blind the driver of an oncoming vehicle and
cause a serious accident, or seriously reduce
your ability to see the road. The headlights
should be checked for proper aim every
12 months (as is done during the MOT test),
and any time a new headlight is fitted or front-
end body work is performed. It should be
emphasised that the following procedure will
only provide a temporary setting until the
headlights can be adjusted by a properly-
equipped garage.
1Each headlight has two adjusting screws,
one controlling up-and-down movement and
one controlling left-and-right movement (see
illustration). It may be necessary to remove
the grille (see Chapter 11) for access to these
screws.
2There are several methods of adjusting the
headlights. The simplest method requires a
blank wall (or garage door) 25 feet in front of
the vehicle, and a level floor.
3Position masking tape vertically on the wall,
to mark the vehicle centreline and the
centreline of both headlights. Note:It may be
easier to position the tape on the wall with the
vehicle parked only a few inches away, and
then move the vehicle back the required
distance when all marks have been made.
4Make a horizontal line on the wall to mark
the centreline of all headlights.
5Move the vehicle back so that it is 25 feet
away from the marked wall (keep the front end
of the vehicle square to the wall). Adjustment
should be made with the vehicle sitting level,
the fuel tank half-full, and with no unusually
heavy loads in the vehicle.
6Switch on the dipped beam. The bright
spots on the wall should be two inches below
the horizontal line, and two inches to the left
of the headlight vertical lines. Adjustment is
made by turning the adjusting screw to raise
or lower the beam. The other adjusting screwshould be used in the same manner to move
the beam left or right.
7With main beam on, the bright spots on the
wall should be exactly on the vertical lines,
and just below the horizontal line. Note:It may
not be possible to position the headlight aim
exactly for both main and dipped beams. If a
compromise must be made, keep in mind that
the dipped beam is most used, and will have
the greatest effect on driver safety.
8Have the headlights adjusted by a dealer
service department or qualified garage at the
earliest opportunity.
14 Headlight housing-
removal and refitting
1
Caution: If the radio in your
vehicle is equipped with an anti-
theft system, make sure you have
the correct activation code
before disconnecting the battery, Refer to
the information on page 0-7 at the front of
this manual before detaching the cable.
Note: If, after connecting the battery, the
wrong language appears on the instrument
panel display, refer to page 0-7 for the
language resetting procedure.
Removal
1Disconnect the battery negative cable.2Remove the side grille (see Chapter 11),
then remove the rear cover(s) where
necessary.
3Unplug the headlight (sealed beam-type) or
remove the bulb (halogen bulb-type).
4Remove the screws and detach the housing
(see illustration).
Refitting
5Refitting is the reverse of removal.
15 Bulb renewal
1
1The lenses of many lights are held in place
by screws, which makes it a simple procedure
to gain access to the bulbs.
2On some lights, the lenses are held in place
by clips. The lenses can be removed by using
a small screwdriver to prise them off.
3Several bulbs are mounted in self-earthing
holders, and are removed by pushing in and
turning them anti-clockwise (see illustration).
The bulbs can then be removed (see
illustrations).
4The tail lights on 3-Series models are
accessible after removing the housing, then
removing the bulbs (see illustrations).
5To gain access to the facia lights, the
instrument cluster will have to be removed
first (see illustration).
12•6 Body electrical systems
15.3c . . . then pull the bulb from the
holder15.3b On models with high-mounted
centre brake lights, the self-earthing
holder is accessible from the luggage area
- pull the holder out . . .15.3a The tail light bulbs on later 5-Series
models are in self-earthing holders which
can be simply pulled out of the housing -
the bulb is then removed from the holder
14.4 Remove the screws (arrowed) and
detach the headlight housing13.1 The headlight adjustment screws
(arrowed) are accessible from the back of
the headlight on 3-Series models

REF•1
REF
MOT Test Checks
This is a guide to getting your vehicle through the MOT test.
Obviously it will not be possible to examine the vehicle to the same
standard as the professional MOT tester. However, working through
the following checks will enable you to identify any problem areas
before submitting the vehicle for the test.
Where a testable component is in borderline condition, the tester
has discretion in deciding whether to pass or fail it. The basis of such
discretion is whether the tester would be happy for a close relative or
friend to use the vehicle with the component in that condition. If the
vehicle presented is clean and evidently well cared for, the tester may
be more inclined to pass a borderline component than if the vehicle is
scruffy and apparently neglected.
It has only been possible to summarise the test requirements here,
based on the regulations in force at the time of printing. Test standards
are becoming increasingly stringent, although there are some
exemptions for older vehicles. For full details obtain a copy of the Haynes
publication Pass the MOT! (available from stockists of Haynes manuals).
An assistant will be needed to help carry out some of these checks.
The checks have been sub-divided into four categories, as follows:
HandbrakeMTest the operation of the handbrake.
Excessive travel (too many clicks) indicates
incorrect brake or cable adjustment.
MCheck that the handbrake cannot be
released by tapping the lever sideways. Check
the security of the lever mountings.
Footbrake
MDepress the brake pedal and check that it
does not creep down to the floor, indicating a
master cylinder fault. Release the pedal, wait
a few seconds, then depress it again. If the
pedal travels nearly to the floor before firm
resistance is felt, brake adjustment or repair is
necessary. If the pedal feels spongy, there is
air in the hydraulic system which must be
removed by bleeding.MCheck that the brake pedal is secure and in
good condition. Check also for signs of fluid
leaks on the pedal, floor or carpets, which
would indicate failed seals in the brake master
cylinder.
MCheck the servo unit (when applicable) by
operating the brake pedal several times, then
keeping the pedal depressed and starting the
engine. As the engine starts, the pedal will
move down slightly. If not, the vacuum hose or
the servo itself may be faulty.
Steering wheel and column
MExamine the steering wheel for fractures or
looseness of the hub, spokes or rim.
MMove the steering wheel from side to side
and then up and down. Check that the
steering wheel is not loose on the column,
indicating wear or a loose retaining nut.
Continue moving the steering wheel as before,
but also turn it slightly from left to right.
MCheck that the steering wheel is not loose
on the column, and that there is no abnormalmovement of the steering wheel, indicating
wear in the column support bearings or
couplings.
Windscreen and mirrors
MThe windscreen must be free of cracks or
other significant damage within the driver’s
field of view. (Small stone chips are
acceptable.) Rear view mirrors must be
secure, intact, and capable of being adjusted.
1Checks carried out
FROM THE DRIVER’S SEAT
1Checks carried out
FROM THE DRIVER’S
SEAT2Checks carried out
WITH THE VEHICLE
ON THE GROUND3Checks carried out
WITH THE VEHICLE
RAISED AND THE
WHEELS FREE TO
TURN4Checks carried out on
YOUR VEHICLE’S
EXHAUST EMISSION
SYSTEM

REF•3
REF
MOT Test Checks
Exhaust system
MStart the engine. With your assistant
holding a rag over the tailpipe, check the
entire system for leaks. Repair or renew
leaking sections.
Jack up the front and rear of the vehicle,
and securely support it on axle stands.
Position the stands clear of the suspension
assemblies. Ensure that the wheels are
clear of the ground and that the steering
can be turned from lock to lock.
Steering mechanism
MHave your assistant turn the steering from
lock to lock. Check that the steering turns
smoothly, and that no part of the steering
mechanism, including a wheel or tyre, fouls
any brake hose or pipe or any part of the body
structure.
MExamine the steering rack rubber gaiters
for damage or insecurity of the retaining clips.
If power steering is fitted, check for signs of
damage or leakage of the fluid hoses, pipes or
connections. Also check for excessive
stiffness or binding of the steering, a missing
split pin or locking device, or severe corrosion
of the body structure within 30 cm of any
steering component attachment point.
Front and rear suspension and
wheel bearings
MStarting at the front right-hand side, grasp
the roadwheel at the 3 o’clock and 9 o’clock
positions and shake it vigorously. Check for
free play or insecurity at the wheel bearings,
suspension balljoints, or suspension mount-
ings, pivots and attachments.
MNow grasp the wheel at the 12 o’clock and
6 o’clock positions and repeat the previous
inspection. Spin the wheel, and check for
roughness or tightness of the front wheel
bearing.
MIf excess free play is suspected at a
component pivot point, this can be confirmed
by using a large screwdriver or similar tool and
levering between the mounting and the
component attachment. This will confirm
whether the wear is in the pivot bush, its
retaining bolt, or in the mounting itself (the bolt
holes can often become elongated).
MCarry out all the above checks at the other
front wheel, and then at both rear wheels.
Springs and shock absorbers
MExamine the suspension struts (when
applicable) for serious fluid leakage, corrosion,
or damage to the casing. Also check the
security of the mounting points.
MIf coil springs are fitted, check that the
spring ends locate in their seats, and that the
spring is not corroded, cracked or broken.
MIf leaf springs are fitted, check that all
leaves are intact, that the axle is securely
attached to each spring, and that there is no
deterioration of the spring eye mountings,
bushes, and shackles.MThe same general checks apply to vehicles
fitted with other suspension types, such as
torsion bars, hydraulic displacer units, etc.
Ensure that all mountings and attachments are
secure, that there are no signs of excessive
wear, corrosion or damage, and (on hydraulic
types) that there are no fluid leaks or damaged
pipes.
MInspect the shock absorbers for signs of
serious fluid leakage. Check for wear of the
mounting bushes or attachments, or damage
to the body of the unit.
Driveshafts
(fwd vehicles only)
MRotate each front wheel in turn and inspect
the constant velocity joint gaiters for splits or
damage. Also check that each driveshaft is
straight and undamaged.
Braking system
MIf possible without dismantling, check
brake pad wear and disc condition. Ensure
that the friction lining material has not worn
excessively, (A) and that the discs are not
fractured, pitted, scored or badly worn (B).
MExamine all the rigid brake pipes
underneath the vehicle, and the flexible
hose(s) at the rear. Look for corrosion, chafing
or insecurity of the pipes, and for signs of
bulging under pressure, chafing, splits or
deterioration of the flexible hoses.
MLook for signs of fluid leaks at the brake
calipers or on the brake backplates. Repair or
renew leaking components.
MSlowly spin each wheel, while your
assistant depresses and releases the
footbrake. Ensure that each brake is operating
and does not bind when the pedal is released.
3Checks carried out
WITH THE VEHICLE RAISED
AND THE WHEELS FREE TO
TURN

REF•7
REF
Tools and Working Facilities
MImpact screwdriver
MMicrometer and/or vernier calipers (see
illustrations)
MDial gauge (see illustration)
MUniversal electrical multi-meter
MCylinder compression gauge
(see illustration)
MClutch plate alignment set (see illustration)
MBrake shoe steady spring cup removal tool
(see illustration)
MBush and bearing removal/installation set
(see illustration)
MStud extractors (see illustration)
MTap and die set (see illustration)
MLifting tackle
MTrolley jack
Buying tools
For practically all tools, a tool factor is the
best source, since he will have a very
comprehensive range compared with the
average garage or accessory shop. Having
said that, accessory shops often offer
excellent quality tools at discount prices, so it
pays to shop around.
Remember, you don’t have to buy the most
expensive items on the shelf, but it is always
advisable to steer clear of the very cheap
tools. There are plenty of good tools around atreasonable prices, but always aim to
purchase items which meet the relevant
national safety standards. If in doubt, ask the
proprietor or manager of the shop for advice
before making a purchase.
Care and maintenance of tools
Having purchased a reasonable tool kit, it is
necessary to keep the tools in a clean and
serviceable condition. After use, always wipe
off any dirt, grease and metal particles using a
clean, dry cloth, before putting the tools away.
Never leave them lying around after they have
been used. A simple tool rack on the garage
or workshop wall for items such as
screwdrivers and pliers is a good idea. Store
all normal spanners and sockets in a metal
box. Any measuring instruments, gauges,
meters, etc, must be carefully stored where
they cannot be damaged or become rusty.
Take a little care when tools are used.
Hammer heads inevitably become marked,
and screwdrivers lose the keen edge on their
blades from time to time. A little timely
attention with emery cloth or a file will soon
restore items like this to a good serviceable
finish.
Working facilities
Not to be forgotten when discussing toolsis the workshop itself. If anything more than
routine maintenance is to be carried out,
some form of suitable working area becomes
essential.
It is appreciated that many an owner-
mechanic is forced by circumstances to
remove an engine or similar item without the
benefit of a garage or workshop. Having done
this, any repairs should always be done under
the cover of a roof.
Wherever possible, any dismantling should
be done on a clean, flat workbench or table at
a suitable working height.
Any workbench needs a vice; one with a
jaw opening of 100 mm is suitable for most
jobs. As mentioned previously, some clean
dry storage space is also required for tools, as
well as for any lubricants, cleaning fluids,
touch-up paints and so on, which become
necessary.
Another item which may be required, and
which has a much more general usage, is an
electric drill with a chuck capacity of at least 8
mm. This, together with a good range of twist
drills, is virtually essential for fitting
accessories.
Last, but not least, always keep a supply of
old newspapers and clean, lint-free rags
available, and try to keep any working area as
clean as possible.
Bush and bearing removal/installation setStud extractor setTap and die set

REF•11
REF
Fault Finding
Engine misses at idle speed
m mSpark plugs worn or incorrectly-gapped (Chapter 1).
m mFaulty spark plug HT leads (Chapter 1).
m mVacuum leaks (Chapter 1).
m mIncorrect ignition timing (Chapter 5).
m mUneven or low compression (Chapter 2).
m mFaulty charcoal canister, 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, or partially-blocked carburettor
jets (Chapter 4).
m mFaulty or incorrectly-gapped spark plugs (Chapter 1).
m mIncorrect ignition timing (Chapter 5).
m mCracked distributor cap, disconnected distributor HT leads, or
damaged distributor components (Chapter 1).
m mFaulty spark plug HT 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).
Engine misfires on acceleration
m mSpark plugs fouled (Chapter 1).
m mFuel injection system or carburettor malfunctioning (Chapter 4).
m mFuel filter clogged (Chapters 1 and 4).
m mIncorrect ignition timing (Chapter 5).
m mIntake manifold air leak (Chapter 4).
Engine surges while holding accelerator steady
m
mIntake air leak (Chapter 4).
m mFuel pump faulty (Chapter 4).
m mLoose fuel injector harness connections (Chapters 4 and 6).
m mDefective ECU (Chapter 5).
Engine lacks power
m
mIncorrect ignition timing (Chapter 5).
m mExcessive play in distributor shaft (Chapter 5).
m mWorn rotor, distributor cap or HT leads (Chapters 1 and 5).
m mFaulty or incorrectly-gapped spark plugs (Chapter 1).
m mFuel injection system or carburettor malfunctioning (Chapter 4).
m mFaulty coil (Chapter 5).
m mBrakes binding (Chapter 1).
m mAutomatic transmission fluid level incorrect (Chapter 1).
m mClutch slipping (Chapter 8).
m mFuel filter clogged and/or impurities in the fuel system (Chapter 1).
m mEmission control system not functioning properly (Chapter 6).
m mLow or uneven cylinder compression pressures (Chapter 2).
Engine stalls
m
mIdle speed incorrect (Chapter 1).
m mFuel filter clogged and/or water and impurities in the fuel system
(Chapter 1).
m mDistributor components damp or damaged (Chapter 5).
m mFaulty emissions system components (Chapter 6).
m mFaulty or incorrectly-gapped spark plugs (Chapter 1).
m mFaulty spark plug HT leads (Chapter 1).
m mVacuum leak in the fuel injection system, intake manifold or
vacuum hoses (Chapter 4).
Engine backfires
m mEmissions system not functioning properly (Chapter 6).
m mIgnition timing incorrect (Chapter 5).
m mFaulty secondary ignition system (cracked spark plug insulator,
faulty plug HT leads, distributor cap and/or rotor) (Chapters 1 and 5).
m mFuel injection system or carburettor malfunctioning (Chapter 4).
m mVacuum leak at fuel injector(s), intake manifold or vacuum hoses
(Chapter 4).
m mValve clearances incorrect (Chapter 1), or valve(s) sticking or
damaged (Chapter 2).
Pinking or knocking engine sounds when
accelerating or driving uphill
m mIncorrect grade of fuel.
m mIgnition timing incorrect (Chapter 5).
m mFuel injection system or carburettor in need of adjustment (Chap-
ter 4).
m mDamaged spark plugs or HT leads, or incorrect type fitted (Chapter 1).
m mWorn or damaged distributor components (Chapter 5).
m mFaulty emission system (Chapter 6).
m mVacuum leak (Chapter 4).
Engine runs with oil pressure light on
Caution: Stop the engine immediately if the oil
pressure light comes on and establish the cause.
Running the engine while the oil pressure is low can
cause severe damage.
m mLow oil level (Chapter 1).
m mIdle speed too low (Chapter 1).
m mShort-circuit in wiring (Chapter 12).
m mFaulty oil pressure sender unit (Chapter 2).
m mWorn engine bearings and/or oil pump (Chapter 2).
Engine runs-on after switching off
m
mIdle speed too high (Chapter 1).
m mExcessive engine operating temperature (Chapter 3).
m mIncorrect fuel octane grade.
m mSpark plugs defective or incorrect grade (Chapter 1).
Engine electrical system
Battery will not hold charge
m
mAlternator drivebelt defective or not adjusted properly (Chapter 1).
m mElectrolyte level low (Chapter 1).
m mBattery terminals loose or corroded (Chapter 1).
m mAlternator not charging properly (Chapter 5).
m mLoose, broken or faulty wiring in the charging circuit (Chapter 5).
m mShort in vehicle wiring (Chapters 5 and 12).
m mInternally-defective battery (Chapters 1 and 5).
m mIgnition (no-charge) warning light bulb blown - on some early
models (Chapter 5)
Ignition (no-charge) warning light fails to go out
m mFaulty alternator or charging circuit (Chapter 5).
m mAlternator drivebelt defective or out of adjustment (Chapter 1).
m mAlternator voltage regulator inoperative (Chapter 5).
Ignition (no-charge) warning light fails to come on
when key is turned
m mWarning light bulb defective (Chapter 12).
m mFault in the printed circuit, wiring or bulbholder (Chapter 12).

REF•14Fault Finding
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 wheel alignment (tracking) 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 mWheel alignment (tracking) incorrect (Chapter 10)
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).
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. Renew the pads
immediately (Chapter 9).
Brake vibration (pedal pulsates)
Note:If the vehicle has ABS, it is normal for the brake pedal to pulsate
when the system is working.
m mExcessive lateral disc run-out (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 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).
Excessive pedal effort required to stop vehicle
m
mMalfunctioning brake servo unit (Chapter 9).
m mPartial system failure (Chapter 9).
m mExcessively-worn pads or shoes (Chapter 9).
m mCaliper piston stuck or sluggish (Chapter 9).
m mBrake pads contaminated with oil or grease (Chapter 9).
m mNew pads fitted and not yet seated. It will take a while for the new
material to seat against the disc.
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).
m mRear drum brake self-adjuster mechanism faulty (when applicable)
(Chapter 9).
Grabbing or uneven braking action
m mMalfunction of brake servo unit (Chapter 9).
m mBinding brake pedal mechanism (Chapter 9).
Brake pedal feels “spongy” when depressed
m
mAir in hydraulic lines (Chapter 9).
m mMaster cylinder mounting bolts loose (Chapter 9).
m mMaster cylinder defective (Chapter 9).
Brake pedal travels to the floor with little resistance
m
mLittle or no fluid in the master cylinder reservoir, caused by leaking
caliper piston(s), loose, damaged or disconnected brake lines
(Chapter 9).
Handbrake does not hold
m mHandbrake linkage incorrectly adjusted (Chapter 9).
m mHandbrake shoe linings worn out or contaminated (Chapter 9).

REF•15
REF
Fault Finding
Suspension and steering
Note:Before assuming that a problem exists, check the following
items:
a) Tyre pressures and tyre condition (also check for out-of-round or
out-of-balance tyres, and bent wheel rims).
b) Steering universal joints from the column to the steering gear (for
play or wear).
c) Front and rear suspension, and the rack-and-pinion assembly (for
loose or damaged parts).
d) Wheel bearings (wheel wobble or roughness when spun).
Vehicle pulls to one side
m mMismatched or uneven tyres (Chapter 10).
m mBroken or sagging springs (Chapter 10).
m mFront wheel or rear wheel alignment incorrect (Chapter 10).
m mFront brake problem (Chapter 9).
Abnormal or excessive tyre wear
m
mFront wheel or rear wheel alignment incorrect (Chapter 10).
m mSagging or broken springs (Chapter 10).
m mTyre out of balance (Chapter 10).
m mWorn shock absorber (Chapter 10).
m mOverloaded vehicle or unsympathetic driving style.
m mTyres not rotated regularly.
Wheel makes a “thumping” noise
m
mBlister or bump on tyre (Chapter 10).
m mFaulty shock absorber action (Chapter 10).
m mWheel bolts loose.
Shimmy, shake or vibration
m
mTyre or wheel out of balance or out of round (Chapter 10).
m mLoose, worn or incorrectly-adjusted wheel bearings (Chapter 1).
m mWorn tie-rod ends (Chapter 10).
m mWorn balljoints (Chapter 10).
m mExcessive wheel run-out (Chapter 10).
m mBlister or bump on tyre (Chapter 10).
m mWheel bolts loose.
High steering effort
m
mLack of lubrication at balljoints, tie-rod ends and steering gear
(Chapter 1).
m mIncorrect front wheel alignment (Chapter 10).
m mLow tyre pressure(s) (Chapter 1).
m mPower steering fluid low, or steering pump drivebelt slipping,
where applicable (Chapter 10)
Poor steering self-centring
m mLack of lubrication at balljoints and tie-rod ends (Chapter 1).
m mBinding in balljoints (Chapter 10).
m mBinding in steering column (Chapter 10).
m mLack of lubricant in steering gear (Chapter 10).
m mInaccurate front wheel alignment (Chapter 10).
Abnormal noise at the front end
m
mLack of lubrication at balljoints and tie-rod ends (Chapter 1).
m mDamaged shock absorber mounting (Chapter 10).
m mWorn control arm bushings or tie-rod ends (Chapter 10).
m mLoose anti-roll bar (Chapter 10).
m mLoose wheel bolts.
m mLoose suspension mounting bolts (Chapter 10).
Wandering or poor steering stability
m
mMismatched or uneven tyres (Chapter 10).
m mLack of lubrication at balljoints and tie-rod ends (Chapter 1).
m mWorn shock absorbers (Chapter 10).
m mLoose anti-roll bar (Chapter 10).
m mBroken or sagging springs (Chapter 10).
m mFront or rear wheel alignment incorrect (Chapter 10).
Erratic steering when braking
m
mWheel bearings worn (Chapter 1).
m mBroken or sagging springs (Chapter 10).
m mLeaking wheel cylinder (rear drum brake models) or caliper
(Chapter 9).
m mWarped discs (Chapter 9).
Excessive pitching and/or rolling around corners or
during braking
m mLoose anti-roll bar (Chapter 10).
m mWorn shock absorbers or mountings (Chapter 10).
m mBroken or sagging springs (Chapter 10).
m mOverloaded vehicle.
Suspension bottoms
m
mOverloaded vehicle.
m mWorn shock absorbers (Chapter 10).
m mBroken or sagging springs, or incorrect springs fitted (Chapter 10).
Unevenly-worn tyres
m
mFront wheel or rear wheel alignment incorrect (Chapter 10).
m mWorn shock absorbers (Chapter 10).
m mWheel bearings worn (Chapter 10).
m mExcessive tyre or wheel run-out (Chapter 10).
m mWorn balljoints (Chapter 10).
Excessive tyre wear on outside edge
m
mTyre pressures incorrect (Chapter 1).
m mExcessive cornering speed.
m mWheel alignment incorrect (excessive toe-in) (Chapter 10).
m mSuspension components damaged (Chapter 10).
Excessive tyre wear on inside edge
m
mTyre pressures incorrect (Chapter 1).
m mWheel alignment incorrect (excessive toe-out) (Chapter 10).
m mLoose or damaged steering components (Chapter 10).
Tyre tread worn in one place
m
mTyres out of balance.
m mDamaged or buckled wheel. Inspect and renew if necessary.
m mDefective tyre (Chapter 1).
Excessive play or looseness in steering system
m
mWheel bearing(s) worn (Chapter 10.
m mTie-rod end loose or worn (Chapter 10).
m mSteering gear mountings loose (Chapter 10).
Rattling or clicking noise in steering gear
m
mInsufficient or incorrect lubricant in rack-and-pinion assembly
(Chapter 10).
m mSteering gear mountings loose (Chapter 10).

REF•18Automotive chemicals and lubricants
A number of automotive chemicals and
lubricants are available for use during vehicle
maintenance and repair. They include a wide
variety of products ranging from cleaning
solvents and degreasers to lubricants and
protective sprays for rubber, plastic and
vinyl.
Cleaners
Carburettor cleaner and choke cleaner
is a strong solvent for gum, varnish and
carbon. Most carburettor cleaners leave a
dry-type lubricant film which will not harden or
gum up. Because of this film, it is not
recommended for use on electrical
components.
Brake system cleaneris used to remove
grease and brake fluid from the brake system,
where clean surfaces are absolutely
necessary. It leaves no residue, and often
eliminates brake squeal caused by
contaminants.
Electrical cleaner removes oxidation,
corrosion and carbon deposits from electrical
contacts, restoring full current flow. It can also
be used to clean spark plugs, carburettor jets,
voltage regulators and other parts where an
oil-free surface is desired.
Moisture dispersantsremove water and
moisture from electrical components such as
alternators, voltage regulators, electrical
connectors and fuse blocks. They are non-
conductive and non-corrosive.
Degreasersare heavy-duty solvents used
to remove grease from the outside of the
engine and from chassis components. They
can be sprayed or brushed on, and are usually
rinsed off with water.
Lubricants
Engine oilis the lubricant formulated for
use in engines. It normally contains a wide
variety of additives to prevent corrosion and
reduce foaming and wear. Engine oil comes in
various weights (viscosity ratings) from 5 to
60. The recommended weight of the oil
depends on the season, temperature and the
demands on the engine. Light oil is used in
cold climates and under light load conditions.
Heavy oil is used in hot climates, and where
high loads are encountered. Multi-viscosity
(multigrade) oils are designed to have
characteristics of both light and heavy oils,
and are available in a number of weights from
5W-20 to 20W-50.
Gear oilis designed to be used in
differentials, manual transmissions and other
areas where high-temperature lubrication is
required.
Chassis and wheel bearing greaseis a
heavy grease used where increased loads and
friction are encountered, such as for wheel
bearings, balljoints, tie-rod ends and universal
joints.High-temperature wheel bearing grease
is designed to withstand the extreme
temperatures encountered by wheel bearings
in disc brake-equipped vehicles. It usually
contains molybdenum disulphide (moly),
which is a dry-type lubricant.
White greaseis a heavy grease for metal-
to-metal applications where water is a
problem. White grease stays soft at both low
and high temperatures, and will not wash off
or dilute in the presence of water.
Assembly lubeis a special extreme-
pressure lubricant, usually containing moly,
used to lubricate high-load parts (such as
main and rod bearings and cam lobes) for
initial start-up of a new engine. The assembly
lube lubricates the parts without being
squeezed out or washed away until the engine
oiling system begins to function.
Silicone lubricants are used to protect
rubber, plastic, vinyl and nylon parts.
Graphite lubricantsare used where oils
cannot be used due to contamination
problems, such as in locks. The dry graphite
will lubricate metal parts while remaining
uncontaminated by dirt, water, oil or acids. It
is electrically conductive, and will not foul
electrical contacts in locks such as the
ignition switch.
Penetrating oilsloosen and lubricate
frozen, rusted and corroded fasteners and
prevent future rusting or freezing.
Heat-sink greaseis a special electrically
non-conductive grease that is used for
mounting electronic ignition modules where it
is essential that heat is transferred away from
the module.
Sealants
RTV sealantis one of the most widely-
used gasket compounds. Made from silicone,
RTV is air-curing; it seals, bonds, waterproofs,
fills surface irregularities, remains flexible,
doesn’t shrink, is relatively easy to remove,
and is used as a supplementary sealer with
almost all low- and medium-temperature
gaskets.
Anaerobic sealantis much like RTV in that
it can be used either to seal gaskets or to form
gaskets by itself. It remains flexible, is solvent-
resistant, and fills surface imperfections. The
difference between an anaerobic sealant and
an RTV-type sealant is in the curing. RTV
cures when exposed to air, while an anaerobic
sealant cures only in the absence of air. This
means that an anaerobic sealant cures only
after the assembly of parts, sealing them
together.
Thread and pipe sealant is used for
sealing hydraulic and pneumatic fittings and
vacuum lines. It is usually made from a Teflon
compound, and comes in a spray, a paint-on
liquid and as a wrap-around tape.
Chemicals
Anti-seize compoundprevents seizing,
chafing, cold welding, rust and corrosion in
fasteners. High-temperature anti-seize,
usually made with copper and graphite
lubricants, is used for exhaust system and
exhaust manifold bolts.
Anaerobic locking compoundsare used
to keep fasteners from vibrating or working
loose, and cure only after installation, in the
absence of air. Medium-strength locking
compound is used for small nuts, bolts and
screws that may be removed later. High-
strength locking compound is for large nuts,
bolts and studs which aren’t removed on a
regular basis.
Oil additivesrange from viscosity index
improvers to chemical treatments that claim
to reduce internal engine friction. It should be
noted that most oil manufacturers caution
against using additives with their oils.
Fuel additivesperform several functions,
depending on their chemical make-up. They
usually contain solvents that help dissolve
gum and varnish that build up on carburettor,
fuel injection and intake parts. They also serve
to break down carbon deposits that form on
the inside surfaces of the combustion
chambers. Some additives contain upper
cylinder lubricants for valves and piston rings,
and others contain chemicals to remove
condensation from the fuel tank.
Miscellaneous
Brake fluidis specially-formulated
hydraulic fluid that can withstand the heat and
pressure encountered in brake systems. It is
poisonous and inflammable. Care must be
taken so this fluid does not come in contact
with painted surfaces or plastics. An opened
container should always be resealed, to
prevent contamination by water or dirt. Brake
fluid absorbs moisture from the air, if left in an
unsealed container.
Weatherstrip adhesiveis used to bond
weatherstripping around doors, windows and
boot lids. It is sometimes used to attach trim
pieces.
Undersealis a petroleum-based, tar-like
substance that is designed to protect metal
surfaces on the underside of the vehicle from
corrosion. It also acts as a sound-deadening
agent by insulating the bottom of the vehicle.
Waxes and polishesare used to help
protect painted and plated surfaces from the
weather. Different types of paint may require
the use of different types of wax and polish.
Some polishes utilise a chemical or abrasive
cleaner to help remove the top layer of
oxidised (dull) paint on older vehicles. In
recent years, many non-wax polishes
containing a wide variety of chemicals such as
polymers and silicones have been introduced.
These non-wax polishes are usually easier to
apply, and last longer than conventional
waxes and polishes.