check engine BMW 3 SERIES 1991 E30 User Guide

Caution: Do not overfill the
reservoir. If too much fluid is
added, remove the excess with a
clean syringe. Refit the cap.
7If frequent topping-up is needed, check the
power steering hoses and connections for
leaks and wear (see Section 10).
8Check the condition and tension of the
drivebelt (see Section 11).
8 Automatic transmission fluid
level check
1
Caution: The use of transmission
fluid other than the type listed in
this Chapter’s Specifications
could result in transmission
malfunctions or failure.
1The automatic transmission fluid should be
carefully maintained. Low fluid level can lead
to slipping or loss of drive, while overfilling
can cause foaming and loss of fluid. Either
condition can cause transmission damage.
2Since transmission fluid expands as it heats
up, the fluid level should only be checked
when the transmission is warm (at normal
operating temperature). If the vehicle has just
been driven over 20 miles (32 km), the
transmission can be considered warm. You
can also check the fluid level when the
transmission is cold. If the vehicle has not
been driven for over five hours and the fluid is
about room temperature (20°C), the
transmission is cold. However, the fluid level
is normally checked with the transmission
warm, to ensure accurate results.
Caution: If the vehicle has just
been driven for a long time at
high speed or in city traffic, in hot
weather, or if it has been pulling
a trailer, an accurate fluid level reading
cannot be obtained. Allow the trans-
mission to cool down for about 30 minutes.
3Immediately after driving the vehicle, park it
on a level surface, apply the handbrake and
start the engine. While the engine is idling,
depress the brake pedal and move theselector lever through all the gear ranges,
beginning and ending in Park.
4The automatic transmission dipstick tube is
located in the left rear corner of the engine
compartment.
5With the engine still idling, pull the dipstick
out of the tube (see illustration), wipe it off
with a clean rag, push it all the way back into
the tube and withdraw it again, then note the
fluid level.
6The level should be between the two marks
(see illustration). If the level is low, add the
specified automatic transmission fluid through
the dipstick tube - use a clean funnel,
preferably equipped with a fine mesh filter, to
prevent spills.
Caution: Be careful not to
introduce dirt into the
transmission when topping up.
7Add just enough of the recommended fluid
to fill the transmission to the proper level. It
takes about half a litre to raise the level from
the low mark to the high mark when the fluid
is hot, so add the fluid a little at a time, and
keep checking the level until it’s correct.
8The condition of the fluid should also be
checked along with the level. If the fluid is
black or a dark reddish-brown colour, or if it
smells burned, it should be changed (see
Section 28). If you are in doubt about its
condition, purchase some new fluid, and
compare the two for colour and smell.
9 Tyre rotation
1
1The tyres can be rotated at the specified
intervals, or whenever uneven wear is noticed.
However, bear in mind that if rotation
succeeds in making all the tyres wear evenly,
you will eventually have to renew all four at
once. Since the vehicle will be raised and the
wheels removed anyway, check the brakes
also (see Section 26). Note: Even if you don’t
rotate the tyres, at least check the wheel bolt
tightness.
2It is recommended that the tyres be rotatedin a specific pattern (see illustration)so that
their direction of rotation remains the same.
3Refer to the information in “Jacking and
towing”at the front of this manual for the
proper procedure to follow when raising the
vehicle and changing a tyre.
4The vehicle must be raised on a hoist or
supported on axle stands to get all four tyres
off the ground. Make sure the vehicle is safely
supported!
5After the rotation procedure is finished,
check and adjust the tyre pressures as
necessary, and be sure to check the wheel
bolt tightness.
10 Underbonnet hose check
and renewal
3
Warning: Renewal of air
conditioning hoses must be left
to a dealer service department or
air conditioning specialist having
the equipment to depressurise the system
safely. Never disconnect air conditioning
hoses or components until the system has
been depressurised.
General
1High temperatures under the bonnet can
cause deterioration of the rubber and plastic
hoses used for various systems. Periodic
inspection should be made for cracks, loose
clamps, material hardening, and leaks.
2Information specific to the cooling system
can be found in Section 22, while the braking
system is covered in Section 26.
3Most (but not all) hoses are secured with
clamps. Where clamps are used, check to be
sure they haven’t lost their tension, allowing
the hose to leak. If clamps aren’t used, make
sure the hose has not expanded and/or
hardened where it slips over the fitting,
allowing it to leak.
Vacuum hoses
4It’s quite common for vacuum hoses,
especially those in the emissions system, to
be colour-coded or identified by coloured
1•13
9.2 The tyre rotation pattern for these
models8.6 With the fluid hot, the level should be
kept between the two dipstick notches,
preferably near the upper one8.5 The automatic transmission fluid
dipstick (arrowed) is located near the
bulkhead on the left side of the engine
compartment
1
Every 6000 miles

stripes moulded into them. Various systems
require hoses with different wall thicknesses,
collapse resistance and temperature
resistance. When fitting new hoses, be sure
the new ones are made of the same material.
5Often the only effective way to check a
hose is to remove it completely from the
vehicle. If more than one hose is removed, be
sure to label the hoses and fittings to ensure
correct refitting.
6When checking vacuum hoses, be sure to
include any plastic T-fittings in the check.
Inspect the connections for cracks which
could cause leakage.
7A small piece of vacuum hose can be used
as a stethoscope to detect vacuum leaks.
Hold one end of the hose to your ear and
probe around vacuum hoses and fittings,
listening for the “hissing” sound characteristic
of a vacuum leak.
Warning: When probing with the
vacuum hose stethoscope, be
careful not to touch moving
engine components such as the
drivebelt, cooling fan, etc.
Fuel hoses
Warning: There are certain
precautions which must be taken
when servicing or inspecting fuel
system components. Work in a
well-ventilated area, and do not allow open
flames (cigarettes, appliance pilot lights,
etc.) or bare light bulbs near the work
area. Mop up any spills immediately, and
do not store fuel-soaked rags where they
could ignite. If you spill any fuel on your
skin, rinse it off immediately with soap and
water. When you perform any kind of work
on the fuel system, wear safety glasses,
and have a fire extinguisher on hand.
8The fuel hoses are usually under pressure,
so if any fuel hoses are to be disconnected,
be prepared to catch spilled fuel.
Warning: On vehicles equipped
with fuel injection, you must
depressurise the fuel system
before servicing the fuel hoses.
Refer to Chapter 4 for details.9Check all rubber fuel hoses for deterioration
and chafing. Check especially for cracks in
areas where the hose bends, and just before
connectors, such as where a hose attaches to
the fuel pump or fuel filter, for example.
10Only high-quality fuel hose should be
used. Never, under any circumstances, use
unreinforced vacuum hose, clear plastic
tubing or water hose for fuel hoses.
11Band-type clamps are commonly used on
fuel hoses. These clamps often lose their
tension over a period of time, and can be
“sprung” during removal. Renew all band-type
clamps with screw clamps whenever a hose is
renewed.
Metal lines
12Sections of metal line are often used
between the fuel pump and fuel injection
system. Check carefully to make sure the line
isn’t bent, crimped or cracked.
13If a section of metal line must be renewed,
use seamless steel tubing only, since copper
and aluminium tubing do not have the
strength necessary to withstand the vibration
caused by the engine.
14Check the metal brake lines where they
enter the master cylinder and brake
proportioning or ABS unit (if used) for cracks
in the lines and loose fittings. Any sign of
brake fluid leakage calls for an immediate
thorough inspection of the braking system.
Power steering hoses
15Check the power steering hoses for leaks,
loose connections and worn clamps. Tighten
loose connections. Worn clamps or leaky
hoses should be renewed.
11 Drivebelt check, adjustment
and renewal
1
Check
1The drivebelts, sometimes called V-belts or
simply “fan” belts, are located at the front of
the engine, and play an important role in the
overall operation of the vehicle and itscomponents. Due to their function and
material make-up, the belts are prone to
failure after a period of time, and should be
inspected and adjusted periodically to prevent
major engine damage.
2The number of belts used on a particular
vehicle depends on the accessories fitted.
Drivebelts are used to turn the alternator,
power steering pump, water pump, and air
conditioning compressor. Depending on the
pulley arrangement, a single belt may be used
to drive more than one of these components.
3With the engine switched off, open the
bonnet and locate the various belts at the
front of the engine. Using your fingers (and a
torch, if necessary), move along the belts,
checking for cracks and separation of the belt
plies. Also check for fraying and glazing,
which gives the belt a shiny appearance (see
illustration). Both sides of the belts should be
inspected, which means you will have to twist
each belt to check the underside.
4The tension of each belt is checked by
pushing firmly with your thumb and seeing
how much the belt moves (deflects). Measure
the deflection with a ruler (see illustration). A
good rule of thumb is that the belt should
deflect 6 mm if the distance from pulley
centre-to-pulley centre is between 180 and
280 mm. The belt should deflect 13 mm if the
distance from pulley centre-to-pulley centre is
between 300 and 400 mm.
Adjustment
5If it is necessary to adjust the belt tension,
either to make the belt tighter or looser, it is
done by moving a belt-driven accessory on its
bracket. (When the same belt drives more
than one accessory, normally only one
accessory is moved when making
adjustment.)
6For each component, there will be an
adjusting bolt and a pivot bolt. Both bolts
must be loosened slightly to enable you to
move the component. On some components,
the drivebelt tension can be adjusted by
turning an adjusting bolt after loosening the
lockbolt (see illustration).
7After the two bolts have been loosened,
1•14
11.6 Loosen the nut on the other end of
the adjuster bolt (arrowed) and turn the
bolt to increase or decrease tension on the
drivebelt11.4 Measuring drivebelt deflection with a
straightedge and ruler11.3 Here are some of the more common
problems associated with drivebelts
(check the belts very carefully to prevent
an untimely breakdown)
Every 6000 miles

move the component away from the engine to
tighten the belt, or towards the engine to
loosen the belt. Hold the accessory in
position, and check the belt tension. If it is
correct, tighten the two bolts until just tight,
then recheck the tension. If the tension is still
correct, tighten the bolts.
8It will often be necessary to use some sort
of lever to move the accessory while the belt
is adjusted. If this must be done to gain the
proper leverage, be very careful not to
damage the component being moved, or the
part being prised against.
Renewal
9To renew a belt, follow the instructions
above for adjustment, but remove the belt
from the pulleys.
10In some cases, you will have to remove
more than one belt, because of their
arrangement on the front of the engine.
Because of this, and the fact that belts will
tend to fail at the same time, it is wise to
renew all belts together. Mark each belt and
its appropriate pulley groove, so all renewed
belts can be fitted in their proper positions.
11It is a good idea to take the old belts with
you when buying new ones, in order to make
a direct comparison for length, width and
design.
12Recheck the tension of new belts after a
few hundred miles.
12 Engine idle speed and CO
level check and adjustment
4
Note:The engine should be at normal
operating temperature, with correct ignition
timing and valve clearances (where
adjustable). The air filter should be in good
condition, and all electrical components
(including the air conditioning, where fitted)
should be switched off.
Carburettor
1Connect a tachometer and exhaust gas
analyser (CO meter) to the engine.
2Start the engine and allow it to idle.
3Check that the idle speed is as given in the
Specifications. Adjustment of the idle speed is
only possible on the 2B4 carburettor. Turn the
carburettor idle speed adjustment screw until
the engine idles at the correct speed (see
illustration).
4If the idle speed is low on the 2BE
carburettor, and all wiring to the carburettor is
in good condition, it is possible to connect a
resistance into the control circuit. This should
be carried out by your BMW dealer.
5Check that the CO reading is as given in the
Specifications. If not, turn the carburettor idle
mixture adjustment screw until the mixture is
correct (see illustration).
L-Jetronic
6Connect a tachometer and CO meter to the
engine. BMW technicians use a special CO
tester with a probe connected into the
exhaust manifold, but the normal type of
tester which locates in the exhaust tailpipe
can be used instead. Note however that on
models with a catalytic converter, meaningful
CO readings will not be obtained at the
tailpipe.
7Start the engine and allow it to idle.
8Check that the idle speed is as given in
Specifications. If not, remove the tamperproof
cap from the throttle housing, and turn the idle
adjustment screw until the speed is correct.
9Check that the CO reading is as given in the
Specifications. The mixture control screw is
located on the airflow meter, and a specialtool (BMW number 13 1 060) may be required
to make the adjustment.
Motronic
10Connect a tachometer and CO meter to
the engine. BMW technicians use a special
CO tester with a probe connected into the
exhaust manifold, but the normal type of
tester which locates in the exhaust tailpipe
may be used instead. Note however that on
models with a catalytic converter, meaningful
CO readings will not be obtained at the
tailpipe.
11It is not possible to adjust the idle speed
manually, as the idle air stabiliser valve is
activated by the electronic control unit. If the
idle speed is not within the specified range
with the engine at normal operating
temperature, check for a leak in the air inlet
system, and also check the operation of the
idle air stabiliser valve (see Chapter 4).
12Check that the CO reading is as given in
the Specifications. If adjustment is required,
prise out the tamperproof plug from the
airflow meter, and turn the adjustment screw
to set the CO content (on some models, an
Allen key will be required). Fit a new
tamperproof plug on completion (see
illustrations).
1•15
12.12a Removing the tamperproof plug
from the airflow meter
12.5 Mixture adjustment screw (2) on the
2B4 carburettor
12.3 Idle speed adjustment screw on the
2B4 carburettor (shown with the
carburettor removed)
12.12b Adjusting the CO on the Motronic
system
1
Every 6000 miles

13 Battery check, maintenance
and charging
2
Check and maintenance
Warning: Certain precautions
must be followed when checking
and servicing the battery.
Hydrogen gas, which is highly
flammable, is always present in the battery
cells, so keep lighted tobacco and all other
flames and sparks away from it. The
electrolyte inside the battery is actually
dilute sulphuric acid, which will cause
injury if splashed on your skin or in youreyes. It will also ruin clothes and painted
surfaces. When disconnecting the battery
cables, always detach the negative cable
first, and connect it last!
1Battery maintenance is an important
procedure, which will help ensure that you are
not stranded because of a dead battery.
Several tools are required for this procedure
(see illustration).
2Before servicing the battery, always switch
off the engine and all accessories, and
disconnect the cable from the negative
terminal of the battery.
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.
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.
3A low-maintenance battery is standard
equipment. The cell caps can be removed and
distilled water can be added, if necessary.
Later models may be fitted with a
“maintenance-free” battery, which is sealed.
4Remove the caps and check the electrolyte
level in each of the battery cells. It must be
above the plates. There’s usually a split-ring
indicator in each cell to indicate the correct
level. If the level is low, add distilled water
only, then refit the cell caps.Caution: Overfilling the cells may
cause electrolyte to spill over
during periods of heavy charging,
causing corrosion and damage to
nearby components.
5If the positive terminal and cable clamp on
your vehicle’s battery is equipped with a
rubber protector, make sure that it’s not torn
or damaged. It should completely cover the
terminal.
6The external condition of the battery should
be checked periodically. Look for damage
such as a cracked case.
7Check the tightness of the battery cable
clamps to ensure good electrical connections.
Check the entire length of each cable, looking
for cracked or abraded insulation and frayed
conductors.
8If corrosion (visible as white, fluffy deposits)
is evident, remove the cables from the
terminals, clean them with a battery brush,
and reconnect them (see illustrations).
Corrosion can be kept to a minimum by fitting
specially treated washers available at car
accessory shops, or by applying a layer of
petroleum jelly or suitable grease to the
Every 12 000 miles or 12 months, whichever comes first
1•16
13.8d When cleaning the cable clamps, all
corrosion must be removed (the inside of
the clamp is tapered to match the taper on
the post, so don’t remove too much
material)
13.8c Regardless of the type of tool used
on the battery posts, a clean, shiny surface
should be the result
13.1 Tools and materials required for
battery maintenance
1 Face shield/safety goggles- When
removing corrosion with a brush, the acidic
particles can easily fly up into your eyes
2 Baking soda - A solution of baking soda and
water can be used to neutralise corrosion
3 Petroleum jelly- A layer of this on the
battery posts will help prevent corrosion
4 Battery post/cable cleaner- This wire-
brush cleaning tool will remove all traces of
corrosion from the battery posts and cable
clamps
5 Treated felt washers- Placing one of
these on each post, directly under the
cable clamps, will help prevent corrosion
6 Puller- Sometimes the cable clamps are
very difficult to pull off the posts, even after
the nut/bolt has been completely loosened.
This tool pulls the clamp straight up and off
the post without damage
7 Battery post/cable cleaner - Here is
another cleaning tool which is a slightly
different version of No 4 above, but it does
the same thing
8 Rubber gloves- Another safety item to
consider when servicing the battery;
remember that’s acid inside the battery!
13.8b Removing a cable from the battery
post with a spanner - sometimes special
battery pliers are required for this
procedure, if corrosion has caused
deterioration of the nut (always remove the
earth cable first, and connect it last!)
13.8a Battery terminal corrosion usually
appears as light, fluffy powder
Every 12 000 miles

terminals and cable clamps after they are
assembled.
9Make sure that the battery carrier is in good
condition, and that the hold-down clamp bolt
is tight. If the battery is removed (see Chap-
ter 5 for the removal and refitting procedure),
make sure that no parts remain in the bottom
of the carrier when it’s refitted. When refitting
the hold-down clamp, don’t overtighten the
bolt.
10Corrosion on the carrier, battery case and
surrounding areas can be removed with a
solution of water and baking soda. Apply the
mixture with a small brush, let it work, then
rinse it off with plenty of clean water.
11Any metal parts of the vehicle damaged
by corrosion should be coated with a zinc-
based primer, then painted.
12Additional information on the battery and
jump starting can be found in Chapter 5 and
the front of this manual.
Charging
Note: The manufacturer recommends the
battery be removed from the vehicle for
charging, because the gas which escapes
during this procedure can damage the paint or
interior, depending on the location of the
battery. Fast charging with the battery cables
connected can result in damage to the
electrical system.
13Remove all of the cell caps (if applicable),
and cover the holes with a clean cloth to
prevent spattering electrolyte. Disconnect thebattery negative cable, and connect the
battery charger leads to the battery posts
(positive to positive, negative to negative),
then plug in the charger. Make sure it is set at
12 volts if it has a selector switch.
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. 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.
14If you’re using a charger with a rate higher
than two amps, check the battery regularly
during charging to make sure it doesn’t
overheat. If you’re using a trickle charger, you
can safely let the battery charge overnight
after you’ve checked it regularly for the first
couple of hours. Where a maintenance-free
battery is fitted, special precautions may be
necessary when charging it (for example, the
charge rate is normally very low). There may
be a warning label on the battery, but if not,
consult a BMW dealer or auto-electrician.
15If the battery has removable cell caps,
measure the specific gravity with a
hydrometer every hour during the last few
hours of the charging cycle. Hydrometers are
available inexpensively from car accessory
shops - follow the instructions that come with
the hydrometer. Consider the battery charged
when there’s no change in the specific gravity
reading for two hours, and the electrolyte in
the cells is gassing (bubbling) freely. The
specific gravity reading from each cell should
be very close to the others. If not, the battery
probably has a bad cell(s), and a new one
should be fitted.
16Some maintenance-free (sealed) batteries
have built-in hydrometers on the top,
indicating the state of charge by the colour
displayed in the hydrometer window.
Normally, a bright-coloured hydrometer
indicates a full charge, and a dark hydrometer
indicates the battery still needs charging.
Check the battery manufacturer’s instructions
to be sure you know what the colours mean.17If the battery is sealed and has no built-in
hydrometer, you can connect a digital
voltmeter across the battery terminals to
check the charge. A fully-charged battery
should read 12.6 volts or higher.
18Further information on the battery and
jump starting can be found in Chapter 5 and
at the front of this manual.
14 Spark plug check and
renewal
1
1Before beginning, obtain the necessary
tools, which will include a spark plug socket
and a set of feeler blades. Special spark plug
gap gauges can be obtained from certain
spark plug manufacturers (see illustration).
2The best procedure to follow when
renewing the spark plugs is to purchase the
new spark plugs beforehand, adjust them to
the proper gap, and then renew each plug one
at a time. When buying the new spark plugs, it
is important to obtain the correct plugs for
your specific engine. This information can be
found in the Specifications section in the front
of this Chapter.
3With the new spark plugs at hand, allow the
engine to cool completely before attempting
plug removal. During this time, each of the
new spark plugs can be inspected for defects
and the gaps can be checked.
4The gap is checked by inserting the proper
thickness gauge between the electrodes at the
tip of the plug (see illustration). The gap
between the electrodes should be the same as
that given in the Specifications. The wire
should just touch each of the electrodes. If the
gap is incorrect, use the notched adjuster to
bend the curved side of the electrode slightly
until the proper gap is achieved (see
illustration). Note: When adjusting the gap of a
new plug, bend only the base of the earth
electrode, do not touch the tip. If the earth
electrode is not exactly over the centre
electrode, use the notched adjuster to align the
two. Check for cracks in the porcelain insulator,
indicating the spark plug should not be used.
1•17
14.4b To change the gap, bend the earth
electrode only, as indicated by the arrows,
and be very careful not to crack or chip the
porcelain insulator surrounding the centre
electrode14.4a Spark plug manufacturers
recommend using a wire-type gauge when
checking the gap - if the wire does not
slide between the electrodes with a slight
drag, adjustment is required
14.1 Tools required for changing spark
plugs
1 Spark plug socket- This will have special
padding inside to protect the spark plug’s
porcelain insulator
2 Torque wrench - Although not mandatory,
using this tool is the best way to ensure the
plugs are tightened properly
3 Ratchet - Standard hand tool to fit the
spark plug socket
4 Extension - Depending on model and
accessories, you may need special
extensions and universal joints to reach one
or more of the plugs
5 Spark plug gap gauge- This gauge for
checking the gap comes in a variety of
styles. Make sure the gap for your engine is
included. Feeler blades may be used
instead
1
Every 12 000 miles

5With the engine cool, remove the HT lead
from one spark plug. Do this by grabbing the
connector at the end of the wire, not the lead
itself (see illustration). Sometimes it is
necessary to use a twisting motion while the
connector and HT lead are pulled free.
6If compressed air is available, use it to blow
any dirt or foreign material away from the
spark plug area. A common bicycle pump will
also work. The idea here is to eliminate the
possibility of debris falling into the cylinder as
the spark plug is removed.
7Place the spark plug socket over the plug,
and remove it from the engine by turning it
anti-clockwise (see illustration).
8Compare the spark plug with those shown
in the accompanying photos to get an
indication of the overall running condition of
the engine.
9Apply a little copper-based anti-seize
compound to the threads of the new spark
plug. Locate the plug into the head, screwing
it in with your fingers until it no longer turns,
then tighten it with the socket. If available, use
a torque wrench to tighten the plug to ensure
that it is seated correctly. The correct torque
figure is included in this Chapter’s Specifi-
cations.10Before pushing the HT lead onto the end of
the plug, inspect it as outlined in Section 15.
11Attach the HT lead to the new spark plug,
again using a twisting motion on the
connector until it is firmly seated on the spark
plug.
12Follow the above procedure for the
remaining spark plugs, renewing them one at
a time to prevent mixing up the spark plug HT
leads.
15 Spark plug HT leads,
distributor cap and rotor -
check and renewal
1
1The spark plug HT leads should be checked
at the recommended intervals, and whenever
new spark plugs are fitted in the engine.
2Begin this procedure by making a visual
check of the spark plug HT leads while the
engine is running. In a darkened garage (make
sure there is ventilation) start the engine and
observe each HT lead. Be careful not to come
into contact with any moving engine parts. If
there is a break in the wire, you will see arcing
or a small spark at the damaged area. If arcing
is noticed, make a note to obtain new HT
leads, then allow the engine to cool.
3Disconnect the battery negative cable.
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. 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.
4The HT leads should be inspected one at a
time to prevent mixing up the firing order,
which is essential for proper engine operation.
5Disconnect the HT lead from the spark
plug. Do not pull on the lead itself, only on the
connector.
6Inspect inside the connector for corrosion,
which will look like a white crusty powder.
Push the HT lead and connector back onto
the end of the spark plug. It should be a tight
fit on the plug end. If it is not, remove the lead
and use pliers to carefully crimp the metal
terminal inside the connector until it fits
securely on the end of the spark plug.
7Using a clean rag, wipe the entire length of
the HT lead to remove any built-up dirt and
grease. Once the lead is clean, check for
burns, cracks and other damage. Do not bend
the lead excessively, since the conductor
might break.
8Disconnect the HT lead from the distributor.
Again, pull only on the connector. Check for
corrosion and a tight fit in the same manner as
the spark plug end. Renew the HT lead in the
distributor if necessary.
9Check the remaining spark plug HT leads,
making sure they are securely fastened at the
distributor and spark plug when the check is
complete.
10If new spark plug HT leads are required,
purchase a set for your specific engine model.
Lead sets are available pre-cut, with the
connectors already fitted. Remove and renew
the HT leads one at a time, to avoid mix-ups
in the firing order.
11Loosen the screws or detach the clips and
remove the distributor cap (see illustration).
Remove the screws (if applicable) and pull the
rotor off the shaft (see illustration). Check the
distributor cap and rotor for wear. Look for
cracks, carbon tracks and worn, burned or
loose contacts (see illustrations). Renew the
cap and rotor if defects are found. It is
common practice to fit a new cap and rotor
whenever new spark plug HT leads are fitted.
When fitting a new cap, remove the HT leads
from the old cap one at a time, and attach
1•18
15.11b Use an Allen key to remove the
screws, then lift the rotor off the shaft
(later models)15.11a On later models, loosen the screws
and detach the distributor cap up so you
can inspect the inside
14.7 Use a socket spanner with an
extension to unscrew the spark plugs14.5 When removing the spark plug HT
leads, pull only on the connector
Every 12 000 miles
Where there might be difficulty in
inserting the spark plugs into the spark
plug holes, or the possibility of cross-
threading them into the head, a short
piece of rubber or plastic tubing can be
fitted over the end of the spark plug.
The flexible tubing will act as a universal
joint to help align the plug with the plug
hole, and should the plug begin to
cross-thread, the hose will slip on the
spark plug, preventing thread damage.

them to the new cap in the exact same
location - do not simultaneously remove all
the HT leads, or firing order mix-ups may
occur.
16 Manual transmission
lubricant level check
1
1The transmission has a filler/level plug
which must be removed to check the lubricant
level. If the vehicle is raised to gain access to
the plug, be sure to support it safely - do not
crawl under a vehicle which is supported only
by a jack!Note:The vehicle should be level to
give an accurate lubricant check.
2Remove the plug from the side of thetransmission (see illustration)and use your
little finger to reach inside the plug from the
housing and feel the lubricant level. It should
be at or very near the bottom of the plug hole.
3If it isn’t, add the recommended lubricant
through the plug hole with a syringe or
squeeze-bottle, until it just starts to run out of
the hole. Refer to “Lubricants and fluids” at
the beginning of this Chapter for the correct
lubricant type. The manual transmissions on
some later or high-performance models are
filled with automatic transmission fluid (ATF).
Such transmissions normally carry a sticker to
this effect near the filler/level plug. Refer to a
BMW dealer if still in doubt.
4Refit the plug and tighten securely. Check
for leaks after the first few miles of driving.
5If regular topping-up is required, this can
only be due to a leak which should be found
and repaired before it becomes serious.17 Differential lubricant level
check
1
1The differential has a filler/level plug which
must be removed to check the lubricant level.
If the vehicle is raised to gain access to the
plug, be sure to support it safely - do notcrawl under the vehicle when it’s supported
only by the jack! Note:The vehicle should be
level to give an accurate lubricant check.
2Remove the filler/level plug from the
differential (see illustration). Use an Allen key
to unscrew the plug.
3Use your little finger as a dipstick to make
sure the lubricant level is up to the bottom of
the plug hole. If not, use a syringe or squeeze-
bottle to add the recommended lubricant until
it just starts to run out of the hole.
4Refit the plug and tighten it securely.
5If regular topping-up is required, this can
only be due to a leak which should be found
and repaired before it becomes serious.
18 Valve clearances -
check and adjustment
3
Note:This procedure does not apply to the
M40 engine, which has automatic adjusters.
1The valve clearances can be checked with
the engine hot or cold, but note that different
values are specified, depending on engine
temperature. If it is wished to check/adjust the
valve clearances with the engine hot, if
necessary start and run the engine until it
reaches normal operating temperature, then
shut it off.
Caution: If the clearances are checked
with the engine hot, extra care
must be taken to avoid burns.
2Remove the valve cover
from the engine (see Chapter 2A).
3Turn the engine as necessary until No 1
piston (front) is at Top Dead Centre (TDC) on
the compression stroke (see Chapter 2A).
4Check the valve clearances for No 1
cylinder. The valve clearances can be found in
the Specifications Section at the beginning of
this Chapter.
5The clearance is measured by inserting the
specified size feeler gauge between the end
of the valve stem and the rocker arm adjusting
eccentric. You should feel a slight amount of
1•19
15.11d The rotor arm should be checked
for wear and corrosion as indicated here
(if in doubt about its condition, buy a new
one)
15.11c Shown here are some of the
common defects to look for when
inspecting the distributor cap (if in doubt
about its condition, fit a new one)
18.6 The valve clearance is adjusted by
turning the eccentric with a wire hook -
once the specified clearance is obtained,
tighten the locknut with a spanner, then
remove the feeler gauge17.2 Remove the differential filler/level
plug with an Allen key, and make sure the
lubricant is level with the bottom of the
hole16.2 Use a large Allen key to remove the
filler/level plug (arrowed) and check the
lubricant level with your little finger. It
should be level with the bottom of the hole
- if it’s low, add lubricant
1
Every 12 000 miles

drag when the feeler gauge is moved back
and forth.
6If the gap is too large or too small, loosen
the locknut, insert a hook made from large-
diameter metal wire, and rotate the eccentric
to obtain the correct gap (see illustration).
7Once the gap has been set, hold the
eccentric in position with the hook, and
retighten the locknut securely. Recheck the
clearance - sometimes it’ll change slightly
when the locknut is tightened. If so, re-adjust
until it’s correct.
8On the M10 engine, the valves are adjusted
in the firing order, which is 1-3-4-2. After
adjusting No 1 cylinder valves, rotate the
crankshaft half a turn (180º), then check and
adjust the valves on No 3 cylinder. Repeat the
procedure on the remaining cylinders.
9On M20 and M30 engines, the valves are
adjusted following the firing order, which is
1-5-3-6-2-4. After adjusting No 1 cylinder
valves, rotate the crankshaft a third of a turn
(120º), then check and adjust the valves on No
5 cylinder. Repeat the procedure for the
remaining cylinders.
10Refit the valve cover (use a new gasket)
and tighten the mounting nuts evenly and
securely.
11Start the engine and check for oil leakage
between the valve cover and the cylinder
head.19 Throttle linkage -
check and lubrication
1
1The throttle linkage should be checked and
lubricated periodically to ensure its proper
operation.
2Check the linkage to make sure it isn’t
binding.
3Inspect the linkage joints for looseness, and
the connections for corrosion and damage,
renewing parts as necessary (see
illustration).
4Lubricate the connections with spray
lubricant or lithium-based grease.
20 Air filter renewal
1
Carburettor engines
1Release the spring clips, then unscrew the
centre nut and lift off the cover.
2Remove the air filter element, and wipe
clean the air cleaner body and cover
3Fit the new air filter element, then refit the
cover using a reversal of the removal
procedure.
Fuel injection engines
4Loosen the clamp on the air intake duct,
and detach the duct (see illustration).5Release the air cleaner cover retaining clips
(see illustration).
6Rotate the cover up, lift it off and lift the
element out, noting which way round it is
fitted (see illustrations).
7Wipe the inside of the air cleaner housing
with a clean cloth, then fit the new element. If
the element is marked TOP, be sure the
marked side faces up.
8Refit the cover and secure the clips.
9Connect the air duct and tighten the clamp
screw.
21 Fuel system check
1
Warning: Fuel is extremely
flammable, so take extra
precautions when you work on
any part of the fuel system. Don’t
smoke, or allow open flames or bare light
bulbs, near the work area. Don’t work in a
garage where a natural gas-type appliance
(such as a water heater or clothes dryer)
with a pilot light is present. Work in a well-
ventilated area. If you spill any fuel on your
skin, rinse it off immediately with soap and
water. When you perform any kind of work
on the fuel system, wear safety glasses,
and have a fire extinguisher on hand. Mop
up spills immediately, but do not store
fuel-soaked rags where they could ignite.
1If you smell fuel while driving or after the
vehicle has been sitting in the sun, inspect the
fuel system immediately.
2Remove the fuel filler cap and inspect it for
damage and corrosion. The gasket should
have an unbroken sealing imprint. If the
gasket is damaged or corroded, fit a new cap.
3Inspect the fuel feed and return lines for
cracks. Make sure that the connections
between the fuel lines and the carburettor or
fuel injection system, and between the fuel
lines and the in-line fuel filter, are tight.
Warning: On fuel injection
models, the fuel system must be
depressurised before servicing
fuel system components, as
outlined in Chapter 4.
1•20
20.6b . . . and lift the air filter
element out20.6a Rotate the cover
upwards . . .
20.5 Use a screwdriver to detach the air
cleaner cover clips20.4 Detach the duct from the air cleaner
housing19.3 Check and lubricate the throttle
linkage at the points shown (arrowed) -
fuel injection engine shown
Every 12 000 miles

4Since some components of the fuel system
- the fuel tank and some of the fuel feed and
return lines, for example - are underneath the
vehicle, they can be inspected more easily
with the vehicle raised on a hoist. If that’s not
possible, raise the vehicle and support it on
axle stands or ramps.
5With the vehicle raised and safely
supported, inspect the fuel tank and filler neck
for punctures, cracks or other damage. The
connection between the filler neck and the
tank is particularly critical. Sometimes a
rubber filler neck will leak because of loose
clamps or deteriorated rubber. Inspect all fuel
tank mounting brackets and straps, to be sure
the tank is securely attached to the vehicle.
Warning: Do not, under any
circumstances, try to repair a fuel
tank (except rubber
components). A welding torch or
any naked flame can easily cause fuel
vapours inside the tank to explode.
6Carefully check all flexible hoses and metal
lines leading away from the fuel tank. Check
for loose connections, deteriorated hoses,
crimped lines, and other damage. Repair or
renew damaged sections as necessary (see
Chapter 4).
22 Cooling system check
1
1Many major engine failures can be
attributed to cooling system problems. If the
vehicle has automatic transmission, the
engine cooling system also plays an importantrole in prolonging transmission life, because it
cools the transmission fluid.
2The engine should be cold for the cooling
system check, so perform the following
procedure before the vehicle is driven for the
day, or after it has been switched off for at
leastthree hours.
3Remove the radiator cap, doing so slowly
and taking adequate precautions against
scalding if the engine is at all warm. Clean the
cap thoroughly, inside and out, with clean
water. Also clean the filler neck on the
radiator. The presence of rust or corrosion in
the filler neck means the coolant should be
changed (see Section 29). The coolant inside
the radiator should be relatively clean and
clear. If it’s rust-coloured, drain the system
and refill with new coolant.
4Carefully check the radiator hoses and the
smaller-diameter heater hoses. Inspect each
coolant hose along its entire length, renewing
any hose which is cracked, swollen or
deteriorated (see illustration). Cracks will
show up better if the hose is squeezed. Pay
close attention to hose clamps that secure the
hoses to cooling system components. Hose
clamps can pinch and puncture hoses,
resulting in coolant leaks.
5Make sure all hose connections are tight. A
leak in the cooling system will usually show up
as white or rust-coloured deposits on the area
adjoining the leak. If wire-type clamps are
used on the hoses, it may be a good idea to
replace them with screw-type clamps.
6Clean the front of the radiator (and, where
applicable, the air conditioning condenser)
with compressed air if available, or a soft
brush. Remove all flies, leaves, etc,
embedded in the radiator fins. Be extremely
careful not to damage the cooling fins or to
cut your fingers on them.
7If the coolant level has been dropping
consistently and no leaks are detected, have
the radiator cap and cooling system pressure-
tested.
23 Exhaust system check
1
1The engine should be cold for this check,
so perform the following procedure before the
vehicle is driven for the day, or after it has
been switched off for at leastthree hours.
Check the complete exhaust system from the
engine to the end of the tailpipe. Ideally, the
inspection should be done with the vehicle on
a hoist, to give unrestricted access. If a hoist
isn’t available, raise the vehicle and support it
securely on axle stands or ramps.
2Check the exhaust pipes and connections
for evidence of leaks, severe corrosion, and
damage. Make sure that all brackets and
mountings are in good condition, and that
they are tight (see illustration).
3At the same time, inspect the underside of
the body for holes, corrosion, open seams,etc. which may allow exhaust gases to enter
the passenger compartment. Seal all body
openings with suitable sealant.
4Rattles and other noises can often be
traced to the exhaust system, especially the
mountings and heat shields. Try to move the
pipes, silencers (and, where applicable, the
catalytic converter). If the components can
come in contact with the body or suspension
parts, re-hang the exhaust system with new
mountings.
5The running condition of the engine may be
checked by inspecting inside the end of the
tailpipe. The exhaust deposits here are an
indication of the engine’s state of tune. If the
pipe is black and sooty, the engine may be
running too rich, indicating the need for a
thorough fuel system inspection.
24 Steering and suspension
check
1
Note: The steering linkage and suspension
components should be checked periodically.
Worn or damaged suspension and steering
linkage components can result in excessive
and abnormal tyre wear, poor ride quality and
vehicle handling, and reduced fuel economy.
For detailed illustrations of the steering and
suspension components, refer to Chapter 10.
Strut/shock absorber check
1Park the vehicle on level ground, turn the
engine off and apply the handbrake. Check
the tyre pressures.
2Push down at one corner of the vehicle,
then release it while noting the movement of
the body. It should stop moving and come to
rest in a level position with one or two
bounces.
3If the vehicle continues to move up and
down, or if it fails to return to its original
position, a worn or weak strut or shock
absorber is probably the reason.
4Repeat the above check at each of the
three remaining corners of the vehicle.
5Raise the vehicle and support it on axle
stands.
6Check the struts/shock absorbers for
evidence of fluid leakage. A light film of fluid is
1•21
22.4 Hoses, like drivebelts, have a habit of
failing at the worst possible time - to
prevent the inconvenience of a blown
radiator or heater hose, inspect them
carefully as shown here
23.2 Check the exhaust system rubber
mountings for cracks
1
Every 12 000 miles

no cause for concern. Make sure that any fluid
noted is from the struts/shocks, and not from
any other source. If leakage is noted, renew
the struts or shock absorbers in axle pairs (or
as a full set).
7Check the struts/shock absorbers to be
sure that they are securely mounted and
undamaged. Check the upper mountings for
damage and wear. If damage or wear is
noted, renew the struts or shock absorbers.
8If the struts or shock absorbers must be
renewed, refer to Chapter 10 for the
procedure. Always renew both units on the
same axle, or the safety of the vehicle may be
compromised. If possible, renew all four as a
set.
Steering and suspension check
9Inspect the steering system components
for damage and distortion. Look for leaks and
damaged seals, boots and fittings.
10Clean the lower end of the steering
knuckle. Have an assistant grasp the lower
edge of the tyre and move the wheel in and
out, while you look for movement at the
steering knuckle-to-axle arm balljoints.
Inspect the balljoint boots for tears (see
illustration). If there is any movement, or the
boots are torn or leaking, the balljoint(s) must
be renewed.
11Grasp each front tyre at the front and rear
edges, push in at the front, pull out at the rear
and feel for play in the steering linkage. If any
free play is noted, check the steering gear
mountings and the track rod balljoints for
looseness. If the steering gear mountings are
loose, tighten them. If the track rods are
loose, the balljoints may be worn (check to
make sure the nuts are tight). Additional
steering and suspension system information
can be found in Chapter 10.
25 Driveshaft gaiter check
1
1The driveshaft gaiters are very important
because they prevent dirt, water and foreign
material from entering and damaging the
constant velocity (CV) joints. External oil and
grease contamination can cause the gaitermaterial to deteriorate prematurely, so it’s a
good idea to wash the gaiters with soap and
water.
2Inspect the gaiters for tears and cracks, as
well as for loose clamps (see illustration). If
there is any evidence of cracks or leaking
lubricant, the gaiter must be renewed (see
Chapter 8).
26 Brake system check
2
Warning: Dust produced by lining
wear and deposited on brake
components may contain
asbestos, which is hazardous to
your health. Do not blow it out with
compressed air, and don’t inhale it! Do not
use petroleum-based solvents to remove
the dust. Brake system cleaner or
methylated spirit should be used to flush
the dust into a drain pan. After the brake
components are wiped with a damp rag,
dispose of the contaminated rag(s) and the
drain pan contents into a covered and
labelled container. Try to use asbestos-
free new parts whenever possible.
Note:In addition to the specified intervals, the
brake system should be inspected each time
the wheels are removed or a malfunction is
indicated. Because of the obvious safety con-
siderations, the following brake system checks
are some of the most important maintenance
procedures you can perform on your vehicle.
Symptoms of brake system
problems
1The disc brakes have built-in electrical wear
indicators which cause a warning light on the
dash to come on when they’re worn to the
renewal point. When the light comes on,
renew the pads immediately, or expensive
damage to the brake discs could result.
2Any of the following symptoms could
indicate a potential brake system defect:
a) Vehicle pulls to one side when the brake
pedal is depressed
b) Brakes make squealing or dragging noises
when applied
c) Brake pedal travel excessived) Brake pedal pulsates (normal if ABS is
working)
e) Brake fluid leaks (usually on the inner side
of the tyre or wheel)
3If any of these conditions are noted, inspect
the brake system immediately.
Brake lines and hoses
Note: Steel brake pipes are used throughout
the brake system, with the exception of
flexible, reinforced hoses at the front wheels
and as connectors at the rear axle. Periodic
inspection of all these lines is very important.
4Park the vehicle on level ground, and
switch off the engine. Remove the wheel
covers. Loosen, but do not remove, the bolts
on all four wheels.
5Raise the vehicle and support it securely on
axle stands.
6Remove the wheels (see “Jacking and
towing” at the front of this book, or refer to
your owner’s handbook, if necessary).
7Check all brake lines and hoses for cracks,
chafing of the outer cover, leaks, blisters, and
distortion. Check the brake hoses at front and
rear of the vehicle for softening, cracks,
bulging, or wear from rubbing on other
components. Check all threaded fittings for
leaks, and make sure the brake hose
mounting bolts and clips are secure.
8If leaks or damage are discovered, they
must be repaired immediately. Refer to
Chapter 9 for detailed brake system repair
procedures.
Disc brakes
9If it hasn’t already been done, raise the
vehicle and support it securely on axle stands.
Remove the front wheels.
10The disc brake calipers, containing the
pads, are now visible. Each caliper has an
outer and an inner pad - all pads should be
checked.
11Note the pad thickness by looking
through the inspection hole in the caliper (see
illustration). If the lining material is 2.0 mm
thick or less, or if it is tapered from end to
end, the pads should be renewed (see
Chapter 9). Keep in mind that the lining
1•22
26.11 Look through the caliper inspection
window to inspect the brake pads - the
pad lining which rubs against the disc can
also be inspected by looking through each
end of the caliper25.2 Gently probe the driveshaft boots to
check for cracks24.10 Inspect the balljoint boots for tears
(arrowed)
Every 12 000 miles