1984 BMW 3 SERIES spark plugs

7 Ignition timing (TCI system)-
check and adjustment
4
Warning: Keep hands, equipment
and wires well clear of the
viscous cooling fan during
adjustment of the ignition timing.
Note:This Section describes the procedure
for checking and adjusting the ignition timing
on engines fitted with the TCI system. On
engines fitted with the Motronic engine
management system, the ignition timing is
controlled by the electronic control unit, and
no adjustment is possible. The timing can be
checked using the following procedure, but no
ignition timing values were available at the
time of writing. If the timing is thought to be
incorrect, refer to a BMW dealer.
1Some special tools are required for this
procedure (see illustration). The engine must
be at normal operating temperature, and the
air conditioning (where fitted) must be
switched off. Make sure the idle speed is
correct.
2Apply the handbrake, and chock the wheels
to prevent movement of the vehicle. The
transmission must be in neutral (manual) or
Park (automatic).
3The timing marks are located on the engine
flywheel (viewed through the timing checkhole in the bellhousing) and/or on the vibration
damper on the front of the engine.
4Where applicable, disconnect the vacuum
hose from the distributor vacuum advance
unit.
5Connect a tachometer and timing light
according to the equipment manufacturer’s
instructions (an inductive pick-up timing light
is preferred). Generally, the power leads for
the timing light are attached to the battery
terminals, and the pick-up lead is attached to
the No 1 spark plug HT lead. The No 1 spark
plug is the one at the front of the engine.
Caution: If an inductive pick-up
timing light isn’t available, don’t
puncture the spark plug HT lead
to attach the timing light pick-up
lead. Instead, use an adapter between the
spark plug and HT lead. If the insulation on
the HT lead is damaged, the secondary
voltage will jump to earth at the damaged
point, and the engine will misfire.
Note:On some models, a TDC transmitter is
fitted for checking the ignition system.
However, a special BMW tester must be
connected to the diagnostic socket to use it,
so unless the special tester is available, a
conventional timing light should be used. The
ignition timing mark may be on the vibration
damper, but if not, normally the TDC mark will
be. If the timing light is of the adjustable delay
type, then the ignition timing may be
determined by zeroing the adjustment, then
turning the adjustment until the TDC marks are
aligned, and then reading off the amount of
advance from the timing light. If a standard
timing light is being used, make a mark on the
vibration damper in accordance with the
specified advance, using the following formula
to calculate the distance from the TDC mark
to the timing mark:
Distance = 2Pr x advance
360
where P = 3.142
r = radius of vibration damper
advance = specified advance
BTDC in degrees
6With the ignition off, loosen the distributor
clamp nut just enough to allow the distributor
to pivot without any slipping.7Make sure the timing light wires are routed
away from the drivebelts and fan, then start
the engine.
8Raise the engine rpm to the specified
speed, and then point the flashing timing light
at the timing marks - be very careful of moving
engine components.
9The mark on the flywheel or vibration
damper will appear stationary. If it’s aligned
with the specified point on the bellhousing or
engine front cover, the ignition timing is
correct (see illustrations).
10If the marks aren’t aligned, adjustment is
required. Turn the distributor very slowly until
the marks are aligned, taking care not to
touch the HT leads.
11Tighten the nut on the distributor clamp,
and recheck the timing.
12Switch off the engine, and remove the
timing light and tachometer. Reconnect the
vacuum hose where applicable.
8 Distributor-
removal and refitting
4
TCI system
Removal
1After carefully marking them for position,
remove the coil HT lead and spark plug HT
leads from the distributor cap (see Chapter 1).
2Remove No 1 spark plug (the one nearest
you when you are standing in front of the
engine).
3Manually rotate the engine to Top Dead
Centre (TDC) on the compression stroke for
No 1 piston (see Chapter 2A)
4Carefully mark the vacuum hoses, if more
than one is present on your distributor.
5Disconnect the vacuum hose(s).
6Disconnect the primary circuit wires from
the distributor.
7Mark the relationship of the rotor tip to the
distributor housing (see illustration). Also
mark the relationship of the distributor
housing to the engine.
5•4 Engine electrical systems
7.1 Tools for checking and adjusting the
ignition timing
1Vacuum plugs- Vacuum hoses will, in
most cases, have to be disconnected and
plugged. Moulded plugs in various shapes
and sizes can be used for this, if wished
2Inductive pick-up timing light- Flashes a
bright, concentrated beam of light when
No 1 spark plug fires. Connect the leads
according to the instructions supplied with
the light
3Distributor spanner - On some models,
the hold-down bolt for the distributor is
difficult to reach and turn with conventional
spanners or sockets. A special spanner like
this must be used
7.9a Flywheel “OT” timing mark 7.9b Flywheel “OZ” timing mark

connect the ohmmeter to coil terminal 1 (-)
and the centre tower. On Motronic systems,
connect the ohmmeter to coil terminal 15 (+)
and the centre tower. Compare the measured
resistance with the values given in the Specifi-
cations in this Chapter.
6If the measured resistances are not close to
those specified, the coil is defective and
should be renewed. Note that the measured
resistance will vary according to the
temperature of the coil, so don’t rush to
condemn the coil if the resistance is only a
little way out.
7It is essential for proper ignition system
operation that all coil terminals and wire leads
be kept clean and dry.
8Refit the coil in its mounting, and reconnect
the wiring. Refitting is the reverse of removal.
10 Impulse generator and
ignition control unit- check
and renewal (TCI system)
3
1The impulse generator (located in the
distributor) and ignition control unit need to be
tested in the event there is no spark at the
spark plugs. Make sure the plug leads,
ignition coil and spark plugs are working
properly (see Sections 6 and 9). There are two
types of control units; Bosch or
Siemens/Telefunken. The two types (see
illustration)can be distinguished by their
electrical connectors. The Bosch type uses a
single, large rectangular connector at the
bottom of the unit, while the
Siemens/Telefunken control unit uses two
round electrical connectors at the front of the
unit.
Check
Voltage supply and earth to ignition
control unit
2With the ignition off, remove the harness
connectors from the ignition control unit (see
illustrations). Connect a voltmeter between
connector terminals 2 and 4 on Bosch
systems, or between terminals 6 and 3 on
Siemens/Telefunken systems.
3Turn the ignition on. There should be
battery voltage on the designated terminals. If
there is no voltage, check the wiring harness
for an open-circuit (see Chapter 12).
4Using an ohmmeter, check for continuity
between connector terminal 2 (Bosch) or 6
(Siemens/Telefunken) and the earth to the
vehicle body. Continuity should exist.
5Using an ohmmeter, check for continuity
between connector terminal 4 (Bosch) or 3
(Siemens/Telefunken) and terminal 15 of the
ignition coil. Continuity should exist.
6If the readings are incorrect, repair the
wiring harness.
Impulse generator signal
7If the ignition control unit is receiving
battery voltage, check the A/C signal voltage
coming from the impulse generator to the
control unit.
5•6 Engine electrical systems
10.2b Check for voltage at terminals 6 and
3 on the control unit electrical connector
(Siemens/Telefunken system shown)10.2a Check for voltage at terminals 2 and
4 on the control unit electrical connector
(Bosch system shown)
1 Coil HT lead
2 Ignition coil
3 Spark plug HT lead
4 Spark plug
5 Ignition control unit (Bosch)
6 Ignition control unit
(Siemens/Telefunken)
7 Wiring harness8 Distributor housing with
centrifugal advance
counterweights
9 Vacuum diaphragm
10 Circlip
11 Impulse generator
12 Trigger wheel
13 Circlip
14 Dust shield15 Ignition rotor
16 Distributor
17 Roll pin
18 Trigger wheel and impulse
generator tabs
19 Cap retaining clip
20 Impulse generator
connector
10.1 Schematic of the ignition components used on engines with the TCI system

On some models, it will be necessary to
release the retaining clip (see illustration).
13Visually examine the canister for leakage
or damage.
14Renew the canister if you find evidence of
damage or leakage.
7 Catalytic converter
1
General description
1To reduce emissions of unburnt
hydrocarbons (HC), carbon monoxide (CO)
and oxides of nitrogen (NOx), the later
vehicles covered by this manual are equipped
with a catalytic converter (see illustration).
The converter contains a ceramic honeycomb
coated with precious metals, which speed up
the reaction between the pollutants listed
previously and the oxygen in the exhaust gas.
The pollutants are oxidised to produce water
(H
2O), nitrogen and carbon dioxide (CO2).
Check
2Visually examine the converter(s) for cracks
or damage. Make sure all nuts and bolts are
tight.
3Inspect the insulation cover (if applicable)
welded onto the converter - it should not be
loose.
Caution: If an insulation cover is
dented so that it touches the
converter housing inside,
excessive heat may be
transferred to the floor.
4Start the engine and run it at idle speed.
5Check for exhaust gas leakage from the
converter flanges. Check the body of each
converter for holes.
Component renewal
6See Chapter 4 for removal and refitting
procedures.
Precautions
7The catalytic converter is a reliable and
simple device, which needs no maintenance
in itself, but there are some facts of which an
owner should be aware, if the converter is to
function properly for its full service life.
(a) DO NOT use leaded (eg UK “4-star”)
petrol in a car equipped with a catalytic
converter - the lead will coat the precious
metals, reducing their converting
efficiency, and will eventually destroy the
converter.
(b) Always keep the ignition and fuel systems
well-maintained in accordance with the
manufacturer’s schedule, as given in
Chapter 1. In particular, ensure that the air
cleaner filter element, the fuel filter (where
fitted) and the spark plugs are renewed at
the correct interval. If the intake air/fuel
mixture is allowed to become too rich due
to neglect, unburned fuel will enter the
catalytic converter, overheating the
element and eventually destroying the
converter.
(c) If the engine develops a misfire, do not
drive the car at all (or at least as little as
possible) until the fault is cured - the
misfire will allow unburned fuel to enter
the converter, which will result in its
overheating, as noted above.
(d) DO NOT push- or tow-start the car - this
will soak the catalytic converter in
unburned fuel, causing it to overheat
when the engine does start - see (b) or (c)
above.
(e) DO NOT switch off the ignition at high
engine speeds - ie do not “blip” the
throttle immediately before switching offthe engine. If the ignition is switched off
at anything above idle speed, unburned
fuel will enter the (very hot) catalytic
converter, with the possible risk of its
igniting on the element and damaging the
converter.
(f) DO NOT use fuel or engine oil additives -
these may contain substances harmful to
the catalytic converter.
(g) DO NOT continue to use the car if the
engine burns oil to the extent of leaving a
visible trail of blue smoke - the unburned
carbon deposits will clog the converter
passages, and reduce its efficiency; in
severe cases, the element will overheat.
(h) Remember that the catalytic converter
operates at very high temperatures -
hence the heat shields on the car’s
underbody - and the casing will become
hot enough to ignite combustible
materials which brush against it. DO NOT,
therefore, park the car in dry
undergrowth, or over long grass or piles
of dead leaves.
(i) Remember that the catalytic converter is
FRAGILE - do not strike it with tools
during servicing work, and take great care
when working on the exhaust system.
Ensure that the converter is well clear of
any jacks or other lifting gear used to raise
the car, and do not drive the car over
rough ground, road humps, etc, in such a
way as to “ground” the exhaust system.
(j) In some cases, particularly when the car
is new and/or is used for stop/start
driving, a sulphurous smell (like that of
rotten eggs) may be noticed from the
exhaust. This is common to many
catalytic converter-equipped cars, and
seems to be due to the small amount of
sulphur found in some petrols reacting
with hydrogen in the exhaust, to produce
hydrogen sulphide (H
2S) gas; while this
gas is toxic, it is not produced in sufficient
amounts to be a problem. Once the car
has covered a few thousand miles, the
problem should disappear - in the
meanwhile, a change of driving style, or of
the brand of petrol used, may effect a
solution.
(k) The catalytic converter, used on a well-
maintained and well-driven car, should
last for 50 000 to 100 000 miles - from
this point on, the CO level should be
carefully checked regularly, to ensure that
the converter is still operating efficiently. If
the converter is no longer effective, it
must be renewed.
6•6 Engine management and emission control systems
7.1 Typical catalytic converter (M10
engine type shown, others similar)6.12 EVAP system charcoal canister
viewed from under the vehicle (316i model)

REF•10Fault Finding
Engine will not rotate when attempting to start
m mBattery terminal connections loose or corroded (Chapter 1).
m mBattery discharged or faulty (Chapter 1).
m mAutomatic transmission not completely engaged in Park (Chap-
ter 7B) or (on models with a clutch switch) clutch not completely
depressed (Chapter 8).
m mBroken, loose or disconnected wiring in the starting circuit
(Chapters 5 and 12).
m mStarter motor pinion jammed in flywheel ring gear (Chapter 5).
m mStarter solenoid faulty (Chapter 5).
m mStarter motor faulty (Chapter 5).
m mIgnition switch faulty (Chapter 12).
m mStarter pinion or flywheel teeth worn or broken (Chapter 5).
m mEngine internal problem (Chapter 2B).
Engine rotates, but will not start
m
mFuel tank empty.
m mBattery discharged (engine rotates slowly) (Chapter 5).
m mBattery terminal connections loose or corroded (Chapter 1).
m mLeaking fuel injector(s), faulty fuel pump, pressure regulator, etc
(Chapter 4).
m mFuel not reaching fuel injection system or carburettor (Chapter 4).
m mIgnition components damp or damaged (Chapter 5).
m mFuel injector stuck open (Chapter 4).
m mWorn, faulty or incorrectly-gapped spark plugs (Chapter 1).
m mBroken, loose or disconnected wiring in the starting circuit
(Chapter 5).
m mLoose distributor mounting bolts causing ignition timing to wander
(Chapters 1 and 5).
m mBroken, loose or disconnected wires at the ignition coil, or faulty
coil (Chapter 5).
Engine hard to start when cold
m mBattery discharged (Chapter 1).
m mFuel system malfunctioning (Chapter 4).
m mInjector(s) leaking or carburettor automatic choke faulty (Chap-
ter 4).
m mDistributor rotor carbon-tracked (Chapter 5).
Engine hard to start when hot
m
mAir filter element clogged (Chapter 1).
m mFuel not reaching the fuel injection system or carburettor (Chap-
ter 4).
m mCorroded battery connections, especially earth (negative)
connection (Chapter 1).
Starter motor noisy or excessively-rough in
engagement
m mPinion or flywheel gear teeth worn or broken (Chapter 5).
m mStarter motor mounting bolts loose or missing (Chapter 5).
Engine starts, but stops immediately
m
mLoose or faulty electrical connections at distributor, coil or
alternator (Chapter 5).
m mInsufficient fuel reaching the fuel injector(s) or carburettor
(Chapters 1 and 4).
m mDamaged fuel injection system speed sensors (Chapter 5).
m mFaulty fuel injection relays (Chapter 5).
Oil puddle under engine
m
mOil sump gasket and/or sump drain plug seal leaking (Chapter 2).
m mOil pressure sender unit leaking (Chapter 2).
m mValve cover gaskets leaking (Chapter 2).
m mEngine oil seals leaking (Chapter 2).
Engine idles erratically
m
mVacuum leakage (Chapter 4).
m mAir filter element clogged (Chapter 1).
m mFuel pump not delivering sufficient fuel to the fuel injection system
or carburettor (Chapter 4).
m mLeaking head gasket (Chapter 2).
m mTiming belt/chain and/or sprockets worn (Chapter 2).
m mCamshaft lobes worn (Chapter 2).
m mFaulty charcoal canister, where fitted (Chapter 6). This Section provides an easy-reference guide to the more
common problems which may occur during the operation of your
vehicle. These problems and their possible causes are grouped under
headings denoting various components or systems, such as Engine,
Cooling system, etc. They also refer you to the Chapter and/or
Section which deals with the problem.
Remember that successful fault diagnosis is not a mysterious
black art practised only by professional mechanics. It is simply the
result of the right knowledge combined with an intelligent, systematic
approach to the problem. Always work by a process of elimination,
starting with the simplest solution and working through to the mostcomplex - and never overlook the obvious. Anyone can run the fuel
tank dry or leave the lights on overnight, so don’t assume that you are
exempt from such oversights.
Finally, always establish a clear idea of why a problem has
occurred, and take steps to ensure that it doesn’t happen again. If the
electrical system fails because of a poor connection, check all other
connections in the system to make sure that they don’t fail as well. If a
particular fuse continues to blow, find out why - don’t just renew one
fuse after another. Remember, failure of a small component can often
be indicative of potential failure or incorrect functioning of a more
important component or system.
Engine

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•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.

REF•19
REF
Buying spare parts & vehicle identification numbers
Buying spare parts
Spare parts are available from many
sources; for example, BMW garages, other
garages and accessory shops, and motor
factors. Our advice regarding spare part
sources is as follows.
Officially-appointed BMW garages- This is
the best source for parts which are peculiar to
your vehicle, and which are not generally
available (eg complete cylinder heads, internal
transmission components, badges, interior
trim etc). It is also the only place at which you
should buy parts if the vehicle is still under
warranty. To be sure of obtaining the correct
parts, it will be necessary to give the storeman
the full Vehicle Identification Number, and if
possible, to take the old parts along for
positive identification. Many parts are
available under a factory exchange scheme -
any parts returned should always be clean. It
obviously makes good sense to go straight to
the specialists on your vehicle for this type of
part, as they are best equipped to supply you.
Other garages and accessory shops- These
are often very good places to buy materials
and components needed for the maintenance
of your vehicle (eg oil filters, spark plugs,
bulbs, drivebelts, oils and greases, touch-up
paint, filler paste, etc). They also sell general
accessories, usually have convenient opening
hours, charge lower prices, and can often be
found not far from home.
Motor factors- Good factors will stock all
the more important components which wearout comparatively quickly (eg exhaust
systems, brake pads, seals and hydraulic
parts, clutch components, bearing shells,
pistons, valves etc). Motor factors will often
provide new or reconditioned components on
a part-exchange basis - this can save a
considerable amount of money.
Vehicle identification
numbers
Modifications are a continuing and
unpublicised process in vehicle manufacture,
quite apart from major model changes. Spare
parts manuals and lists are compiled upon a
numerical basis, the appropriate identification
number or code being essential to correct
identification of the component concerned.When ordering spare parts, always give as
much information as possible. Quote the
vehicle model, year of manufacture, Vehicle
Identification Number and engine numbers, as
appropriate.
The Vehicle Identification Number (VIN)is
located on the right-hand front wheel arch
next to the front suspension strut upper
mounting, on the driver’s door, and on a plate
on top of the facia, just inside the windscreen
(see illustrations).
The engine number is stamped on a
machined face on the left-hand side of the
cylinder block, near the base of the oil level
dipstick tube.
The body numberis located on the seam
between the left-hand front wing and inner
panel.
The VIN (arrowed) is stamped on the
bulkheadThe VIN is also present on the edge of the
driver’s door