1985 BMW 3 SERIES battery type

0•6Safety First!
Working on your car can be dangerous.
This page shows just some of the potential
risks and hazards, with the aim of creating a
safety-conscious attitude.
General hazards
Scalding
• Don’t remove the radiator or expansion
tank cap while the engine is hot.
• Engine oil, automatic transmission fluid or
power steering fluid may also be dangerously
hot if the engine has recently been running.
Burning
• Beware of burns from the exhaust system
and from any part of the engine. Brake discs
and drums can also be extremely hot
immediately after use.
Crushing
• When working under or near
a raised vehicle,
always
supplement the
jack with axle
stands, or use
drive-on
ramps.
Never
venture
under a car which
is only supported by a jack.
• Take care if loosening or tightening high-
torque nuts when the vehicle is on stands.
Initial loosening and final tightening should
be done with the wheels on the ground.
Fire
• Fuel is highly flammable; fuel vapour is
explosive.
• Don’t let fuel spill onto a hot engine.
• Do not smoke or allow naked lights
(including pilot lights) anywhere near a
vehicle being worked on. Also beware of
creating sparks
(electrically or by use of tools).
• Fuel vapour is heavier than air, so don’t
work on the fuel system with the vehicle over
an inspection pit.
• Another cause of fire is an electrical
overload or short-circuit. Take care when
repairing or modifying the vehicle wiring.
• Keep a fire extinguisher handy, of a type
suitable for use on fuel and electrical fires.
Electric shock
• Ignition HT
voltage can be
dangerous,
especially to
people with heart
problems or a
pacemaker. Don’t
work on or near the
ignition system with
the engine running or
the ignition switched on.• Mains voltage is also dangerous. Make
sure that any mains-operated equipment is
correctly earthed. Mains power points should
be protected by a residual current device
(RCD) circuit breaker.
Fume or gas intoxication
• Exhaust fumes are
poisonous; they often
contain carbon
monoxide, which is
rapidly fatal if inhaled.
Never run the
engine in a
confined space
such as a garage
with the doors shut.
• Fuel vapour is also
poisonous, as are the vapours from some
cleaning solvents and paint thinners.
Poisonous or irritant substances
• Avoid skin contact with battery acid and
with any fuel, fluid or lubricant, especially
antifreeze, brake hydraulic fluid and Diesel
fuel. Don’t syphon them by mouth. If such a
substance is swallowed or gets into the eyes,
seek medical advice.
• Prolonged contact with used engine oil can
cause skin cancer. Wear gloves or use a
barrier cream if necessary. Change out of oil-
soaked clothes and do not keep oily rags in
your pocket.
• Air conditioning refrigerant forms a
poisonous gas if exposed to a naked flame
(including a cigarette). It can also cause skin
burns on contact.
Asbestos
• Asbestos dust can cause cancer if inhaled
or swallowed. Asbestos may be found in
gaskets and in brake and clutch linings.
When dealing with such components it is
safest to assume that they contain asbestos.
Special hazards
Hydrofluoric acid
• This extremely corrosive acid is formed
when certain types of synthetic rubber, found
in some O-rings, oil seals, fuel hoses etc, are
exposed to temperatures above 400
0C. The
rubber changes into a charred or sticky
substance containing the acid. Once formed,
the acid remains dangerous for years. If it
gets onto the skin, it may be necessary to
amputate the limb concerned.
• When dealing with a vehicle which has
suffered a fire, or with components salvaged
from such a vehicle, wear protective gloves
and discard them after use.
The battery
• Batteries contain sulphuric acid, which
attacks clothing, eyes and skin. Take care
when topping-up or carrying the battery.
• The hydrogen gas given off by the battery
is highly explosive. Never cause a spark or
allow a naked light nearby. Be careful when
connecting and disconnecting battery
chargers or jump leads.
Air bags
• Air bags can cause injury if they go off
accidentally. Take care when removing the
steering wheel and/or facia. Special storage
instructions may apply.
Diesel injection equipment
• Diesel injection pumps supply fuel at very
high pressure. Take care when working on
the fuel injectors and fuel pipes.
Warning: Never expose the hands,
face or any other part of the body
to injector spray; the fuel can
penetrate the skin with potentially fatal
results.
Remember...
DO
• Do use eye protection when using power
tools, and when working under the vehicle.
• Do wear gloves or use barrier cream to
protect your hands when necessary.
• Do get someone to check periodically
that all is well when working alone on the
vehicle.
• Do keep loose clothing and long hair well
out of the way of moving mechanical parts.
• Do remove rings, wristwatch etc, before
working on the vehicle – especially the
electrical system.
• Do ensure that any lifting or jacking
equipment has a safe working load rating
adequate for the job.
A few tips
DON’T
• Don’t attempt to lift a heavy component
which may be beyond your capability – get
assistance.
• Don’t rush to finish a job, or take
unverified short cuts.
• Don’t use ill-fitting tools which may slip
and cause injury.
• Don’t leave tools or parts lying around
where someone can trip over them. Mop
up oil and fuel spills at once.
• Don’t allow children or pets to play in or
near a vehicle being worked on.

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

Flushing
7Once the system is completely drained,
flush the radiator with fresh water from a
garden hose until the water runs clear at the
drain or bottom hose. If the radiator is
severely corroded, damaged or leaking, it
should be removed (see Chapter 3) and taken
to a radiator repair specialist.
8Flushing in this way will remove sediments
from the radiator, but will not remove rust and
scale from the engine and cooling tube
surfaces. These deposits can be removed by
using a chemical cleaner. Follow the
procedure outlined in the cleaner
manufacturer’s instructions. Remove the
cylinder block drain plug before flushing the
engine.
9On models so equipped, remove the
overflow hose from the coolant recovery
reservoir. Drain the reservoir and flush it with
clean water, then reconnect the hose.
Refilling
10Tighten the radiator drain plug, or
reconnect the radiator bottom hose. Refit and
tighten the cylinder block drain plug.
Four-cylinder engines
11Slowly add new coolant (a 40%/60%
mixture of antifreeze to water) to the radiator
until it is full. Add coolant to the reservoir up
to the lower mark.
12Leave the radiator cap off, and run the
engine in a well-ventilated area until the
thermostat opens (coolant will begin flowing
through the radiator, and the upper radiator
hose will become hot).
13Turn the engine off, and let it cool. Add
more coolant mixture to bring the coolant
level back up to the lip on the radiator filler
neck. On the M40 engine, unscrew the bleed
screw from the top of the radiator, and add
coolant until it comes out of the bleed screw
hole. Refit and tighten the bleed screw.
14Squeeze the upper radiator hose to expel
air, then add more coolant mixture if
necessary. Refit the radiator cap.
15Start the engine, allow it to reach normal
operating temperature, and check for leaks.
Six-cylinder engines
16Loosen the bleed screw in the thermostat
housing (see illustration)
17Fill the radiator with a 40%/60% solution
of antifreeze and water until it comes out of
the bleed screw opening. Tighten the bleed
screw.
18Refit the radiator cap, and run the engine
until the thermostat opens (the upper radiator
hose will become hot). Slowly loosen the
bleed screw until no bubbles emerge, then
tighten the screw.
19Repeat the procedure until the air is bled
from the system.
30 Fuel filter renewal
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. 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.
1On fuel injection engines, depressurise the
fuel system (see Chapter 4).
2The fuel filter is located in the engine
compartment on the bulkhead, or under the
vehicle adjacent to the fuel tank.
3Because on some models the filter is
located adjacent to the starter motor, fuel
could leak onto the electrical connections. For
safety reasons, therefore, disconnect the
battery negative cable before beginning work.
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.
4Place a pan or rags under the fuel filter to
catch any spilled fuel. If suitable hose clamps
are available, clamp the inlet and outlet hoses.
5 Detach the hoses and remove the bracket
screws/nuts, then remove the filter and where
applicable the bracket assembly (see
illustration).
6Detach the filter from the bracket.
7Refitting is the reverse of removal. Be sure
the arrow on the filter points in the direction of
fuel flow.
31 Manual transmission
lubricant change
1
1Tools necessary for this job include axle
stands to support the vehicle in a raised
position, an Allen key to remove the drain
plug, a drain pan, newspapers and clean rags.
The correct amount of the specified lubricant
should also be available (see “Lubricants and
fluids”at the start of this Chapter).
2The lubricant should be drained when it is
hot (ie immediately after the vehicle has been
driven); this will remove any contaminants
better than if the lubricant were cold. Because
1•25
30.5 To renew the fuel filter, disconnect
the hoses (A), then unscrew the nut (B) and
detach the filter from the bracket (fuel
injection type shown)29.16 The bleed screw (arrowed) is
located on the thermostat housing (six-
cylinder models)29.4 Radiator drain plug location
(arrowed) - not fitted to all models
31.5 Use an Allen key to remove the drain
plug (arrowed) from the bottom of the
transmission
1
Every 24 000 miles

12After the No 1 piston has been positioned
at TDC on the compression stroke, TDC for
any of the remaining pistons can be located
by turning the crankshaft and following the
firing order. Mark the remaining spark plug
lead terminal locations just like you did for the
No 1 terminal, then number the marks to
correspond with the cylinder numbers. As you
turn the crankshaft, the rotor will also turn.
When it’s pointing directly at one of the marks
on the distributor, the piston for that particular
cylinder is at TDC on the compression stroke.
4 Valve cover-
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.
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.
2Detach the breather hose from the valve
cover.
3On M20 engines, unbolt and remove the
intake manifold support bracket and, if
applicable, the bracket for the engine sensors
or idle air stabiliser (it will probably be
necessary to disconnect the electrical
connectors from the sensors and stabiliser).
4On M30 engines, disconnect the electrical
connector for the airflow sensor. Unclip the
electrical harness, moving it out of the way.
5Where necessary on M30 engines, remove
the hoses and fittings from the intake air hose,
then loosen the clamp and separate the hose
from the throttle body. Unscrew the mounting
nuts for the air cleaner housing, and remove
the housing together with the air hose and
airflow sensor.
6Remove the valve cover retaining nuts and
washers (see illustrations). Where necessary,
disconnect the spark plug lead clip or coverfrom the stud(s), and set it aside. It will usually
not be necessary to disconnect the leads from
the spark plugs.
7Remove the valve cover and gasket.
Discard the old gasket. On the M40 engine,
also remove the camshaft cover (see
illustrations). If applicable, remove the semi-
circular rubber seal from the cut-out at the
front of the cylinder head.
Refitting
8Using a scraper, remove all traces of old
gasket material from the sealing surfaces of
the valve cover and cylinder head.
Caution: Be very careful not to
scratch or gouge the delicate
aluminium surfaces. Gasket
removal solvents are available at
motor factors, and may prove helpful.
After all gasket material has been
removed, the gasket surfaces can be
degreased by wiping them with a rag
dampened with a suitable solvent.
9If applicable, place a new semi-circular
rubber seal in the cut-out at the front of the
cylinder head, then apply RTV-type gasket
sealant to the joints between the seal and the
mating surface for the valve cover gasket.
Note:After the sealant is applied, you should
refit the valve cover and tighten the nuts within
ten minutes.
10Refit the camshaft cover (M40 engine), the
valve cover and a new gasket. Refit the
washers and nuts; tighten the nuts evenly and
securely. Don’t overtighten these nuts - theyshould be tight enough to prevent oil from
leaking past the gasket, but not so tight that
they warp the valve cover.
11The remainder of refitting is the reverse of
removal.
5 Intake manifold-
removal and refitting
2
Removal
1Allow the engine to cool completely, then
relieve the fuel pressure on fuel-injection
engines (see Chapter 4).
2Disconnect 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.
3Drain the engine coolant (see Chapter 1)
below the level of the intake manifold. If the
coolant is in good condition, it can be saved
and reused.
4On fuel injection engines, loosen the hose
clamp and disconnect the large air inlet hose
from the throttle body. It may also be
necessary to remove the entire air
cleaner/inlet hose assembly to provide
enough working room (see Chapter 4).
2A•4 In-car engine repair procedures
4.7b Removing the camshaft cover on the
M40 engine4.7a Removing the valve cover on the
M40 engine4.7c Removing the valve cover gasket on
the M40 engine
4.6b Valve cover bolt locations (arrowed)
on M20 six-cylinder engines4.6a Valve cover bolt locations (arrowed)
on M10 four-cylinder engines

8 Timing chain and
sprockets- removal,
inspection and refitting
5
Note:This procedure applies to M10 and M30
engines.
Caution: Once the engine is set
at TDC, do not rotate the
camshaft or crankshaft until the
timing chain is reinstalled. If the
crankshaft or camshaft is rotated with the
timing chain removed, the valves could hit
the pistons, causing expensive internal
engine damage.
Removal
1Position the No 1 cylinder at Top Dead
Centre (TDC) on the compression stroke (see
Section 3).
2Remove the valve cover (see Section 4).
Double-check that the No 1 cylinder is at TDC
on the compression stroke by making sure the
No 1 cylinder rocker arms are loose (not
compressing their valve springs).
3Remove the upper timing chain cover (see
Section 7). Note the location of the camshaft
timing marks, which should now be aligned.
On four-cylinder (M10) engines, there’s
usually a stamped line on the camshaft flange
that aligns with a cast mark on the top of the
cylinder head; also, the camshaft sprocket
dowel pin hole will be at its lowest point. On
six-cylinder (M30) engines, a line drawn
through two of the camshaft sprocket bolts
opposite each other would be exactly vertical,
while a line drawn through the other two bolts
would be horizontal. Additionally, the locating
pin should be in the lower left corner (between
the 7 and 8 o’clock positions). Be sure you’ve
identified the correct camshaft TDC position
before dismantling, because correct valve
timing depends on you aligning them exactly
on reassembly. Note:As the engine is
mounted in the engine compartment at anangle, all references to horizontal and vertical
whilst timing the camshafts are in relation to
the crankshaft, and not the ground.
4Hold the crankshaft stationary with a socket
and ratchet on the vibration damper centre bolt,
then loosen (but don’t unscrew completely) the
four bolts attaching the camshaft sprocket to
the camshaft. Be very careful not to rotate the
camshaft or crankshaft. Note:Some earlier
models may have locking tabs for the camshaft
sprocket bolts. Bend the tabs down before
loosening the bolts. The tabs are no longer
available from the manufacturer, and do not
have to be used on refitting.
5Remove the lower timing chain cover (see
Section 7).
6Unscrew and remove the four camshaft
sprocket bolts, then disengage the chain from
the crankshaft sprocket and carefully remove
the chain and camshaft sprocket from the
engine. It may be necessary to gently prise
the camshaft sprocket loose from the
camshaft with a screwdriver.
Inspection
Timing sprockets
7Examine the teeth on both the crankshaft
sprocket and the camshaft sprocket for wear.
Each tooth forms an inverted V. If worn, the
side of each tooth under tension will be
slightly concave in shape when compared
with the other side of the tooth (i.e. one side of
the inverted V will be concave when
compared with the other, giving the teeth a
hooked appearance). If the teeth appear to be
worn, the sprockets must be renewed. Note:
The crankshaft sprocket is a press fit on the
crankshaft, and can be removed with a jaw-
type puller after the Woodruff key and oil
pump are removed (see Section 14). However,
BMW recommends the new sprocket be
pressed onto the crankshaft after being
heated to 80°C (175°F) on the M10 engine, or
to 200°C(390°F) on the M30 engine. For this
reason, if the crankshaft sprocket requires
renewal, we recommend removing the
crankshaft (see Part B of this Chapter) and
taking it to an engineering works to have the
old sprocket pressed off and a new one
pressed on.
Timing chain
8The chain should be renewed if the
sprockets are worn or if the chain is loose
(indicated by excessive noise in operation).
It’s a good idea to renew the chain anyway if
the engine is stripped down for overhaul. The
rollers on a very badly worn chain may be
slightly grooved. To avoid future problems, if
there’s any doubt at all about the chain’s
condition, renew it.
Chain rail and tensioner
9Inspect the chain guide rail and tensioner
rail for deep grooves caused by chain contact.
Renew them if they are excessively worn. The
rails can be renewed after removing the
circlips with a pointed tool or needle-nose
pliers (see illustration).10Shake the tensioner plunger, and listen for
a rattling sound from the check ball. If you
can’t hear the ball rattling, renew the plunger.
11To further check the tensioner plunger,
blow through it first from the closed end, then
from the slotted (guide) end. No air should
flow through the plunger when you blow
through the closed end, and air should flow
through it freely when you blow through the
slotted end. If the tensioner fails either test,
renew it.
Refitting
12Refit the tensioner rail and chain guide
rail, if removed.
13Temporarily refit the lower timing chain
cover and vibration damper, so you can check
the crankshaft timing marks. Once you’ve
verified the TDC marks are aligned, remove
the damper and cover.
14Loop the timing chain over the crankshaft
sprocket, then loop it over the camshaft
sprocket and, guiding the chain between the
chain guide and tensioner rail, refit the
camshaft sprocket on the camshaft. Make
sure the camshaft timing marks are aligned.
15The remainder of refitting is the reverse of
removal. Be sure to tighten the fasteners to
the correct torques (see this Chapter’s Speci-
fications).
9 Timing belt covers-
removal and refitting
2
Note:This procedure applies to M20 and M40
engines.
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.
1Disconnect the battery negative cable.
2Remove the fan clutch and fan shroud (see
Chapter 3).
3On the M20 engine, remove the radiator
(see Chapter 3).
4Remove the fan drivebelt pulley.
2A•8 In-car engine repair procedures
9.6a Unbolt the distributor cap
(M40 engine) . . .
8.9 To remove the tensioner or chain guide
rail, remove the circlips with a pointed tool
or needle-nose pliers - the circlips tend to
fly off when they’re released, so make sure
you catch them or they’ll get lost (or,
worse, wind up in the engine!)

22Using a scraper, remove all traces of old
gasket material from the sealing surfaces of
the covers and engine block.
Caution: Be very careful not to
scratch or gouge the delicate
aluminium surfaces. Also, do not
damage the sump gasket, and
keep it clean. Gasket removal solvents are
available at motor factors, and may
prove helpful. After all gasket material has
been removed, the gasket surfaces
can be degreased by wiping them
with a rag dampened with a suitable
solvent.
23Support the cover on two blocks of wood,
and drive out the seals from behind with a
hammer and screwdriver. Be very careful not
to damage the seal bores in the process.
24Coat the outside diameters and lips of the
new seals with multi-purpose grease, and
drive the seals into the cover with a hammer
and a socket slightly smaller in diameter than
the outside diameter of the seal.
25Apply a film of RTV-type gasket sealant to
the surface of the sump gasket that mates
with the front cover. Apply extra beads of RTV
sealant to the edges where the gasket meets
the engine block. Note:If the sump gasket is
damaged, instead of fitting a whole new
gasket, you might try trimming the front
portion of the gasket off at the point where it
meets the engine block, then trim off the front
portion of a new sump gasket so it’s exactly
the same size. Cover the exposed inside area
of the sump with a rag, then clean all traces of
old gasket material off the area where the
gasket was removed. Attach the new gasket
piece to the sump with contact-cement-type
gasket adhesive, then apply RTV-type sealant
as described at the beginning of this
paragraph.
26Coat both sides of the new gasket with
RTV-type gasket sealant, then attach the front
cover to the front of the engine, carefully
working the seals over the crankshaft and
intermediate shaft. Refit the bolts and tighten
them evenly to the torque listed in this
Chapter’s Specifications. Work from bolt-to-
bolt in a criss-cross pattern, to be sure they’re
tightened evenly.Note 1:Tighten the front
cover-to-block bolts first, then tighten the
sump-to-cover bolts. Note 2:After applying
RTV-type sealant, reassembly must be
completed in about 10 minutes so the RTV
won’t prematurely harden.
27The remainder of refitting is the reverse of
removal.
Crankshaft front seal (M40 engines)
28Remove the timing belt and crankshaft
sprocket (see Section 10).
29Remove the Woodruff key from the
groove in the end of the crankshaft.
30Note the fitted position of the oil seal, then
prise it out from the front cover using a
screwdriver, but take care not to damage the
bore of the cover or the surface of thecrankshaft. If the seal is tight, drill two small
holes in the metal end of the seal, and use two
self-tapping screws to pull out the seal. Make
sure all remains of swarf are removed.
31Coat the outside diameter and lip of the
new seal with multi-purpose grease, then
drive it into the cover with a hammer and a
socket slightly smaller in diameter than the
outside diameter of the seal. Make sure the
seal enters squarely.
32The remainder of refitting is the reverse of
removal. Note that it is recommended that the
timing belt be renewed - see Section 10.
12 Cylinder head-
removal and refitting
5
Removal
1Relieve the fuel pressure on all fuel injection
engines (see Chapter 4).
2Disconnect the negative cable from the
battery. Where the battery is located in the
engine compartment, the battery may be
removed completely (see Chapter 5).
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.
3Remove the air cleaner assembly (see
Chapter 4).
4Disconnect the wiring from the distributor
(mark all wiring for position first, if necessary),
and the HT lead from the coil (see Chapter 5).
5Disconnect the lead from the coolant
temperature sender unit (see Chapter 3).
6Disconnect the fuel lines from the fuel rail or
carburettor as applicable (see Chapter 4).
7Drain the cooling system (see Chapter 3).
8Clearly label then disconnect all other
hoses from the throttle body, intake manifold,
carburettor and cylinder head, as applicable.
9Disconnect the throttle cable from the
throttle linkage or carburettor (see Chapter 4).
10Disconnect the exhaust manifold from the
cylinder head (see Section 6). Depending on
the engine type, It may not be necessary to
disconnect the manifold from the exhaust
pipe; however, on right-hand-drive models,
the steering column intermediate shaft may
not allow the manifold to clear the studs on
the cylinder head.
11Remove or disconnect any remaining
hoses or lines from the intake manifold,
including the ignition advance vacuum line(s),
and the coolant and heater hoses.
12On early carburettor models, disconnect
the wiring from the alternator and starter
motor.13Remove the intake manifold (see Sec-
tion 5). Do not dismantle or remove any fuel
injection system components unless it is
absolutely necessary.
14Remove the fan drivebelt and fan (see
Chapter 3).
15Remove the valve cover and gasket (see
Section 4). Remove the semi-circular rubber
seal from the front of the cylinder head, where
this is not incorporated in the valve cover
gasket.
16Set No 1 piston at Top Dead Centre on
the compression stroke (see Section 3).
17Remove the timing chain or belt (see
Section 8 or 10). Note:If you want to save
time by not removing and refitting the timing
belt or chain and re-timing the engine, you can
unfasten the camshaft sprocket and suspend
it out of the way - with the belt or chain still
attached - by a piece of rope. Be sure the
rope keeps firm tension on the belt or chain,
so it won’t become disengaged from any of
the sprockets.
18Loosen the cylinder head bolts a quarter-
turn at a time each, in the reverse of the
tightening sequence shown (see illustrations
12.30a, 12.30b, 12.30c or 12.30d). Do
notdismantle or remove the rocker arm
assembly at this time on M10, M20 and M30
engines.
19Remove the cylinder head by lifting it
straight up and off the engine block. Do not
prise between the cylinder head and the
engine block, as damage to the gasket sealing
surfaces may result. Instead, use a blunt bar
positioned in an intake port to gently prise the
head loose.
20Remove any remaining external
components from the head to allow for
thorough cleaning and inspection. See
Chapter 2B for cylinder head servicing
procedures. On the M40 engine, remove the
rubber O-ring from the groove in the top of the
oil pump/front end cover housing.
Refitting
21The mating surfaces of the cylinder head
and block must be perfectly clean when the
head is refitted.
22Use a gasket scraper to remove all traces
of carbon and old gasket material, then clean
the mating surfaces with a suitable solvent. If
there’s oil on the mating surfaces when the
head is refitted, the gasket may not seal
correctly, and leaks could develop. When
working on the block, stuff the cylinders with
clean rags to keep out debris. Use a vacuum
cleaner to remove material that falls into the
cylinders.
23Check the block and head mating
surfaces for nicks, deep scratches and other
damage. If the damage is slight, it can be
removed with a file; if it’s excessive,
machining may be the only alternative.
24Use a tap of the correct size to chase the
threads in the head bolt holes, then clean the
holes with compressed air - make sure that
In-car engine repair procedures 2A•13
2A

otherwise a small brush or even a bicycle tyre
pump will work). The idea is to prevent dirt
from getting into the cylinders as the
compression check is being done.
3Remove all the spark plugs from the engine
(see Chapter 1).
4Block the throttle wide open, or have an
assistant hold the throttle pedal down.
5On carburettor models, disconnect the LT
lead from the coil. On fuel injection models,
disable the fuel pump and ignition circuit by
removing the main relay(see illustration).
This is to avoid the possibility of a fire from
fuel being sprayed in the engine
compartment. The location of the main relay is
generally near the fuse panel area under the
bonnet, but refer to Chapter 12 for the
specific location on your model.
6Fit the compression gauge in the No 1
spark plug hole (No 1 cylinder is nearest the
radiator).
7Turn the engine on the starter motor over at
least seven compression strokes, and watch
the gauge. The compression should build up
quickly in a healthy engine. Low compression
on the first stroke, followed by gradually-
increasing pressure on successive strokes,
indicates worn piston rings. A low
compression reading on the first stroke, which
doesn’t build up during successive strokes,
indicates leaking valves or a blown head
gasket (a cracked head could also be the
cause). Deposits on the undersides of the
valve heads can also cause low compression.
Record the highest gauge reading obtained.
8Repeat the procedure for the remaining
cylinders, and compare the results to the
compression listed in this Chapter’s Specifi-
cations.
9If compression was low, add some engine
oil (about three squirts from a plunger-type oil
can) to each cylinder, through the spark plug
hole, and repeat the test.
10If the compression increases after the oil
is added, the piston rings are definitely worn.
If the compression doesn’t increasesignificantly, the leakage is occurring at the
valves or head gasket. Leakage past the
valves may be caused by burned valve seats
and/or faces or warped, cracked or bent
valves.
11If two adjacent cylinders have equally low
compression, there’s a strong possibility that
the head gasket between them is blown. The
appearance of coolant in the combustion
chambers or the crankcase would verify this
condition.
12If one cylinder is 20 percent lower than the
others, and the engine has a slightly rough
idle, a worn exhaust lobe on the camshaft
could be the cause.
13If the compression is unusually high, the
combustion chambers are probably coated
with carbon deposits. If that’s the case, the
cylinder head should be removed and
decarbonised.
14If compression is way down, or varies
greatly between cylinders, it would be a good
idea to have a leak-down test performed by a
garage. This test will pinpoint exactly
where the leakage is occurring and how
severe it is.
4 Engine removal-
methods and precautions
If you’ve decided that an engine must be
removed for overhaul or major repair work,
several preliminary steps should be taken.
Locating a suitable place to work is
extremely important. Adequate work space,
along with storage space for the vehicle, will
be needed. If a workshop or garage isn’t
available, at the very least a flat, level, clean
work surface made of concrete or asphalt is
required.
Cleaning the engine compartment and
engine before beginning the removal
procedure will help keep tools clean and
organised.
An engine hoist or A-frame will also be
necessary. Make sure the equipment is rated
in excess of the combined weight of the
engine and accessories. Safety is of primary
importance, considering the potential hazards
involved in lifting the engine out of the vehicle.
If the engine is being removed by a novice,
a helper should be available. Advice and aid
from someone more experienced would also
be helpful. There are many instances when
one person cannot simultaneously perform all
of the operations required when lifting the
engine out of the vehicle.
Plan the operation ahead of time. Arrange
for or obtain all the tools and equipment you’ll
need prior to beginning the job. Some of the
equipment necessary to perform engine
removal and refitting safely and with relative
ease are (in addition to an engine hoist) a
heavy-duty trolley jack, complete sets of
spanners and sockets as described in thefront of this manual, wooden blocks, and
plenty of rags and cleaning solvent for
mopping up spilled oil, coolant and fuel. If the
hoist must be hired, make sure that you
arrange for it in advance, and perform all of
the operations possible without it beforehand.
This will save you money and time.
Plan for the vehicle to be out of use for
quite a while. A machine shop will be required
to perform some of the work which the do-it-
yourselfer can’t accomplish without special
equipment. These establishments often have
a busy schedule, so it would be a good idea
to consult them before removing the engine,
in order to accurately estimate the amount of
time required to rebuild or repair components
that may need work.
Always be extremely careful when removing
and refitting the engine. Serious injury can
result from careless actions. Plan ahead, take
your time and a job of this nature, although
major, can be accomplished successfully.
Warning: The air conditioning
system is under high pressure.
Do not loosen any fittings or
remove any components until
after the system has been discharged by a
qualified engineer. Always wear eye
protection when disconnecting air
conditioning system fittings.
Caution: If removing the M40
engine, it is important not to turn
the engine upside-down for
longer than 10 minutes since it is
possible for the oil to drain out of the
hydraulic tappets. This would render the
tappets unserviceable, and damage could
possibly occur to the engine when it is
next started up.
5 Engine- removal and refitting
3
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.
Removal1Relieve the fuel system pressure (see
Chapter 4), then disconnect the negative
cable from the battery.
2Cover the wings and front panel, and
remove the bonnet (see Chapter 11). Special
pads are available to protect the wings, but an
old bedspread or blanket will also work.
3Remove the air cleaner housing and intake
ducts (see Chapter 4).
4Drain the cooling system (see Chapter 1).
5Label the vacuum lines, emissions system
hoses, wiring connectors, earth straps and
fuel lines, to ensure correct refitting, then
General engine overhaul procedures 2B•5
3.5 As a safety precaution, before
performing a compression check, remove
the cover and the main relay (arrowed)
from the left side of the engine
compartment to disable the fuel and
ignition systems (525i model shown, other
models similar)
2B