1991 BMW 3 SERIES Torque wrench

0•8Roadside Repairs
Jacking and wheel
changing
The jack supplied with the vehicle should
be used only for raising the vehicle when
changing a tyre or placing axle stands under
the frame.
Warning:Never crawl under the
vehicle or start the engine when
this jack is being used as the
only means of support.
When changing a wheel, the vehicle should
be on level ground, with the handbrake firmly
applied, and the wheels chocked. Select
reverse gear (manual transmission) or Park
(automatic transmission). Prise off the hub
cap (if equipped) using the tapered end of the
wheel brace. Loosen the wheel bolts half a
turn, leaving them in place until the wheel is
raised off the ground.
Position the head of the jack under the side
of the vehicle, making sure it engages with thepocket made for this purpose (just behind the
front wheel, or forward of the rear wheel).
Engage the wheel brace handle and turn it
clockwise until the wheel is raised off the
ground. Unscrew the bolts, remove the wheel
and fit the spare.
Refit the wheel bolts and tighten them
finger-tight. Lower the vehicle by turning the
wheel brace anti-clockwise. Remove the jack
and tighten the bolts in a diagonal pattern to
the torque listed in the Chapter 1
Specifications. If a torque wrench is not
available, have the torque checked by a BMW
dealer or tyre fitting specialist as soon as
possible. Refit the hubcap.
Towing
Vehicles with manual transmission can be
towed with all four wheels on the ground, if
necessary. Automatic transmission-equipped
vehicles can only be towed with all fourwheels on the ground providing that the
speed does not exceed 35 mph and the
distance is not over 50 miles, otherwise
transmission damage can result. For
preference, regardless of transmission type,
the vehicle should be towed with the driven
(rear) wheels off the ground.
Proper towing equipment, specifically
designed for the purpose, should be used,
and should be attached to the main structural
members of the vehicle, not to the bumpers or
bumper brackets. Sling-type towing
equipment must notbe used on these
vehicles.
Safety is a major consideration while
towing. The handbrake should be released,
and the transmission should be in neutral. The
steering must be unlocked (ignition switch
turned to position “1”). Remember that
power-assisted steering (where fitted) and the
brake servo will not work with the engine
switched off.
Jacking, towing and wheel changing

Tyre pressures (cold) - bars (psi)Front Rear
3-Series, E30
316 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.9 (28) 2.1 (30)
316i
Saloon . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.0 (29) 2.1 (30)
Estate . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.0 (29) 2.2 (32)
318i . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.8 (26) 1.9 (28)
320i . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.9 (28) 2.0 (29)
325i . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.2 (32) 2.3 (33)
5-Series, E28 (“old-shape”)
518 and 518i . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.0 (29) 2.0 (29)
525i and 528i . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.2 (32) 2.2 (32)
535i and M535i . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.3 (33) 2.5 (36)
5-Series, E34 (“new-shape”)
518i . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.0 (29) 2.0 (29)
520i . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.2 (32) 2.1 (30)
525i, 530i and 535i . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.0 (29) 2.3 (33)
Torque wrench settingsNm
Automatic transmission sump bolts
Three-speed . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 to 9
Four-speed . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 to 7
Spark plugs
M10 engines . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20 to 30
Except M10 engines . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30 to 33
Oxygen sensor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30 to 33
Wheel bolts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 100
Lubricants and fluids
Component or system Lubricant type/specification
Engine . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Multigrade engine oil, viscositySAE 10W/40 to 20W/50, to API SG
Cooling system . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Ethylene glycol-based antifreeze with corrosion inhibitors
Manual transmission* . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Gear oil, viscosity SAE 80 to API-GL4, or single-grade mineral-based
engine oil, viscosity SAE 20, 30 or 40 to API-SG
Automatic transmission . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Dexron ll type ATF
Final drive . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . BMW-approved hypoid gear oil, viscosity SAE 90**
Brake and clutch hydraulic systems . . . . . . . . . . . . . . . . . . . . . . . . . . Hydraulic brake fluid to SAE J 1703 or DOT 4
Power steering . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Dexron ll type ATF
* E34 520i & 525i with air conditioning, E34 530i & 535i - Dexron II type ATF)
** Only available in bulk; refer to your BMW dealer
Capacities*
1•3
1
Engine oil
M10 engines . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.0 litres
M20 engines . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.3 litres
M30 engines . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.8 litres
M40 engines . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.0 litres
Cooling system
M10 engines . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7.0 litres
M20 engines . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10.5 litres
M30 engines . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12.0 litres
M40 engines . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7.0 litres
Fuel tank
3-Series, E30
Saloon . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 55 litres (early),
64 litres (later)
Estate . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 63 litres (early),
70 litres (later)
5-Series
E28 (“old-shape”) . . . . . . . . . . . . . . . . . . . . . . . . 70 litres
E34 (“new-shape”) . . . . . . . . . . . . . . . . . . . . . . . 81 litresManual transmission
ZF . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.2 litres
Getrag . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.0 to 1.5 litres
Automatic transmission (refill)
3-speed . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.0 litres
4-speed . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.0 litres
Final drive capacity (drain and refill)
3-Series, E30 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0.9 litres
5-Series, E28 (“old-shape”) . . . . . . . . . . . . . . . . . . 0.9 litres
5-Series, E34 (“new-shape”) . . . . . . . . . . . . . . . . . 1.7 litres
*All capacities approximate
Servicing Specifications

1 Introduction
This Chapter is designed to help the home
mechanic maintain his or her vehicle with the
goals of maximum performance, economy,
safety and reliability in mind. Included is a
master maintenance schedule, followed by
procedures dealing specifically with each item
on the schedule. Visual checks, adjustments,
component renewal and other helpful items
are included. Refer to the accompanying
illustrations of the engine compartment and
the underside of the vehicle for the locations
of various components. Servicing the vehicle,
in accordance with the mileage/time
maintenance schedule and the step-by-step
procedures, will result in a planned
maintenance programme that should produce
a long and reliable service life. Keep in mind
that it is a comprehensive plan, so maintaining
some items but not others at specified
intervals, will not produce the same results.
2 Routine maintenance
As you service the vehicle, you will discover
that many of the procedures can - and should
- be grouped together, because of the nature
of the particular procedure you’re performing,
or because of the close proximity of two
otherwise-unrelated components to one
another. For example, if the vehicle is raised
for chassis lubrication, you should inspect the
exhaust, suspension, steering and fuelsystems while you’re under the vehicle. When
the wheels are removed for other work, it
makes good sense to check the brakes, since
the wheels are already removed. Finally, let’s
suppose you have to borrow a torque wrench.
Even if you only need it to tighten the spark
plugs, you might as well check the torque of
as many critical nuts and bolts as time allows.
The first step in this maintenance
programme is to prepare yourself before the
actual work begins. Read through all the
procedures you’re planning to do, then gather
up all the parts and tools needed. If it looks
like you might run into problems during a
particular job, seek advice from a mechanic or
an experienced do-it-yourselfer.
3 Engine “tune-up”-
general information
The term “tune-up” is used in this manual to
represent a combination of individual
operations rather than one specific procedure.
If, from the time the vehicle is new, the
routine maintenance schedule is followed
closely, and frequent checks are made of fluid
levels and high-wear items, as suggested
throughout this manual, the engine will be
kept in relatively good running condition, and
the need for additional work will be minimised.
More likely than not, however, there will be
times when the engine is running poorly due
to a lack of regular maintenance. This is even
more likely if a used vehicle, which has not
received regular and frequent maintenance
checks, is purchased. In such cases, an
engine tune-up will be needed outside of the
regular maintenance intervals. The first step in any tune-up or diagnostic
procedure to help correct a poor-running
engine is a cylinder compression check. A
compression check (see Chapter 2B) will help
determine the condition of internal engine
components, and should be used as a guide
for tune-up and repair procedures. If, for
instance, a compression check indicates
serious internal engine wear, a conventional
tune-up will not improve the performance of
the engine, and would be a waste of time and
money. Because of its importance, the
compression check should be done by
someone with the right equipment, and the
knowledge to use it properly.
The following procedures are those most
often needed to bring a generally poor-
running engine back into a proper state of
tune.
Minor tune-up
Check all engine-related fluids (Section 4)
Check all underbonnet hoses (Section 10)
Check and adjust the drivebelts (Sec-
tion 11)
Clean, inspect and test the battery (Sec-
tion 13)
Renew the spark plugs (Section 14)
Inspect the spark plug HT leads, distributor
cap and rotor (Section 15)
Check the air filter (Section 20)
Check the cooling system (Section 22)
Major tune-up
All items listed under minor tune-up, plus . . .
Check the ignition system (see Chapter 5)
Check the charging system (see Chapter 5)
Check the fuel system (see Chapter 4)
Renew the spark plug HT leads, distributor
cap and rotor (Section 15)
1•7
1
Routine Maintenance
Weekly checks
4 Fluid level checks
1
Note:The following are fluid level checks to
be done on a 250-mile or weekly basis.
Additional fluid level checks can be found in
specific maintenance procedures which
follow. Regardless of intervals, be alert to fluid
leaks under the vehicle, which would indicate
a fault to be corrected immediately.
1Fluids are an essential part of the
lubrication, cooling, brake and windscreen
washer systems. Because the fluids gradually
become depleted and/or contaminated during
normal operation of the vehicle, they must be
periodically replenished. See “Lubricants and
fluids”at the beginning of this Chapter before
adding fluid to any of the following
components. Note:The vehicle must be on
level ground when any fluid levels are
checked.
Engine oil
2Engine oil is checked with a dipstick, which
is located on the side of the engine (refer to
the underbonnet illustrations in this Chapter
for dipstick location). The dipstick extends
through a metal tube down into the sump.
3The engine oil should be checked before
the vehicle has been driven, or at least
15 minutes after the engine has been shut off.
4Pull the dipstick out of the tube, and wipe
all of the oil away from the end with a clean
rag or paper towel. Insert the clean dipstick all
the way back into the tube, and pull it out
again. Note the oil at the end of the dipstick.
At its highest point, the oil should be betweenthe two notches or marks (see illustration).
5It takes one litre of oil to raise the level from
the lower mark to the upper mark on the
dipstick. Do not allow the level to drop below
the lower mark, or oil starvation may cause
4.4 The oil level should be kept between
the two marks, preferably at or near the
upper one - if it isn’t, add enough oil to
bring the level to the upper mark
If the oil is checked
immediately after driving the
vehicle, some of the oil will
remain in the upper part of
the engine, resulting in an inaccurate
reading on the dipstick.

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.

Torque wrench settingsNm
Timing chain tensioner plug . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35
Timing belt tensioner bolts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22
Camshaft sprocket-to-camshaft bolt
M10 and M30 engines . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
M20 and M40 engines . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 65
Flange to camshaft (M30 engine) . . . . . . . . . . . . . . . . . . . . . . . . . . . . 145
Timing chain or belt covers-to-engine
M6 bolts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
M8 bolts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22
M10 (bolt size) bolts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47
Crankshaft pulley bolts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22
Crankshaft hub bolt or nut
M10 engine . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 190
M20 engine . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 410
M30 engine . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 440
M40 engine . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 310
Cylinder head bolts*
M10 four-cylinder engine
Stage 1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 60
Stage 2 (wait 15 minutes) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Angle-tighten an additional 33°
Stage 3 (engine at normal operating temperature) . . . . . . . . . . . . . Angle-tighten an additional 25°
M20 six-cylinder engine with hex-head bolts
Stage 1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40
Stage 2 (wait 15 minutes) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 60
Stage 3 (engine at normal operating temperature) . . . . . . . . . . . . . Angle-tighten an additional 25°
M20 six-cylinder engine with Torx-head bolts
Stage 1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30
Stage 2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Angle-tighten an additional 90°
Stage 3 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Angle-tighten an additional 90°
M30 six-cylinder engine (up to and including 1987 model year)
Stage 1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 60
Stage 2 (wait 15 minutes) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Angle-tighten an additional 33°
Stage 3 (engine at normal operating temperature) . . . . . . . . . . . . . Angle-tighten an additional 33°
M30 six-cylinder engine (from 1988 model year)
Stage 1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 60
Stage 2 (wait 20 minutes) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 80
Stage 3 (engine at normal operating temperature) . . . . . . . . . . . . . Angle-tighten an additional 35°
M40 four-cylinder engine
Stage 1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30
Stage 2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Angle-tighten an additional 90°
Stage 3 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Angle-tighten an additional 90°
Intake manifold-to-cylinder head bolts
M8 bolt . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22
M7 bolt . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
M6 bolt . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
Exhaust manifold-to-cylinder head nuts
M6 nut . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
M7 nut . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
Flywheel/driveplate bolts
Manual transmission . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 105
Automatic transmission . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 120
Intermediate shaft sprocket bolt (M20 engines) . . . . . . . . . . . . . . . . . . . 60
Sump-to-block bolts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 to 11
Oil pump bolts (except M40 engines) . . . . . . . . . . . . . . . . . . . . . . . . . . . 22
Oil pump sprocket bolts (M10 and M30 engines) . . . . . . . . . . . . . . . . . 10
Oil pump cover plate-to-engine front end cover (M40 engines) . . . . . . . 9
Front end cover-to-engine bolts (M20 and M40 engines)
M6 bolts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
M8 bolts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22
Crankshaft rear oil seal retainer-to-block bolts
M6 bolts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
M8 bolts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22
* BMW recommend that the cylinder head bolts are renewed as a matter of course.
2A•2 In-car engine repair procedures

Pistons and piston rings
Piston diameter (standard)
M10 engines . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 88.97 mm
M20 engines
B20 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 79.98 mm
B25 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 83.98 mm
M30 engines
B30M
Alcan . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 88.970 mm
KS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 88.980 mm
B35M
Alcan . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 91.972 mm
Mahle . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 91.980 mm
M40 engines
Factory stage 0 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 83.985 mm
Factory stage 00 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 84.065 mm
Piston-to-cylinder wall clearance
New
M10 and M30 engines . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0.02 to 0.05 mm
M20 and M40 engines . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0.01 to 0.04 mm
Service limit
Except B25 engine . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0.15 mm
B25 engine . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0.12 mm
Piston ring end gap
M10 engine
Top compression ring . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0.30 to 0.70 mm
Second compression ring . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0.20 to 0.40 mm
Oil ring . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0.25 to 0.50 mm
M20 engine
All rings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0.20 to 0.50 mm
M30 engine
Top compression ring . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0.20 to 0.45 mm
Second compression ring . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0.40 to 0.65 mm
Oil ring . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0.30 to 0.60 mm
M40 engine
Top compression ring . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0.20 to 1.00 mm
Second compression ring . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0.20 to 1.00 mm
Oil ring
B16 engine . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0.20 to 1.00 mm
B18 engine . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0.40 to 1.40 mm
Piston ring side clearance
M10 engine
Top compression ring . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0.06 to 0.09 mm
Second compression ring . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0.03 to 0.072 mm
Oil ring . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0.02 to 0.06 mm
M20 engine
Top compression ring . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0.04 to 0.08 mm
Second compression ring . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0.03 to 0.07 mm
Oil ring . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0.02 to 0.05 mm
M30 engine
Top compression ring . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0.04 to 0.072 mm
Second compression ring . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0.03 to 0.062 mm
Oil ring . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0.02 to 0.055 mm
M40 engine
Top compression ring . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0.02 to 0.20 mm
Second compression ring . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0.02 to 0.10 mm
Oil ring
B16 engine . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0.02 to 0.10 mm
B18 engine . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Not measured
Torque wrench settingsNm
Main bearing cap-to-engine block bolts*
M10, M20 and M30 engines . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 60
M40 engines
Stage 1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20
Stage 2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Angle-tighten an additional 50°
General engine overhaul procedures 2B•3
2B

Torque wrench settings (continued)Nm
Connecting rod cap bolts/nuts
M10 and M30 engines . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 55
M20 and M40 engines
Stage 1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20
Stage 2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Angle-tighten an additional 70°
Camshaft bearing caps (M40 engine) . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
Intermediate shaft sprocket-to-shaft bolt (M20 engine) . . . . . . . . . . . . . 60
Oil supply tube bolt(s)
M6 (normal) and M8 (banjo) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
M5 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
* BMW recommend that the main bearing bolts are renewed as a matter of course.
2B•4 General engine overhaul procedures
1 General information
Included in this Part of Chapter 2 are the
general overhaul procedures for the cylinder
head and engine internal components.
The information ranges from advice
concerning preparation for an overhaul and
the purchase of new parts to detailed,
paragraph-by-paragraph procedures covering
removal and refitting of internal components
and the inspection of parts.
The following Sections have been written
based on the assumption that the engine has
been removed from the vehicle. For
information concerning in-vehicle engine
repair, as well as removal and refitting of the
external components necessary for the
overhaul, see Chapter 2A, and Section 7 of
this Part.
The Specifications included in this Part are
only those necessary for the inspection and
overhaul procedures which follow. Refer to
Part A for additional Specifications.
2 Engine overhaul-
general information
It’s not always easy to determine when, or
if, an engine should be completely
overhauled, as a number of factors must be
considered.
High mileage is not necessarily an
indication that an overhaul is needed, while
low mileage doesn’t preclude the need for an
overhaul. Frequency of servicing is probably
the most important consideration. An engine
that’s had regular and frequent oil and filter
changes, as well as other required
maintenance, will most likely give many
thousands of miles of reliable service.
Conversely, a neglected engine may require
an overhaul very early in its life.
Excessive oil consumption is an indication
that piston rings, valve seals and/or valve
guides are in need of attention. Make sure
that oil leaks aren’t responsible before
deciding that the rings and/or guides are
worn. Perform a cylinder compression check
to determine the extent of the work required
(see Section 3).Check the oil pressure: Unscrew the oil
pressure sender unit, and connect an oil
pressure gauge in its place. Measure the oil
pressure with the engine at its normal
operating temperature. Compare your
readings to the oil pressures listed in this
Chapter’s Specifications. If the readings are
significantly below these (and if the oil and oil
filter are in good condition), the crankshaft
bearings and/or the oil pump are probably
worn out. On M10 and M30 engines, the oil
pressure sender unit is located high on the left
rear of the cylinder head. On M20 engines, the
sender unit is threaded into the side of the
engine block, below the oil filter. On M40
engines, the sender unit is threaded into the
rear of the oil filter housing.
Loss of power, rough running, knocking or
metallic engine noises, excessive valve train
noise and high fuel consumption may also
point to the need for an overhaul, especially if
they’re all present at the same time. If a
complete tune-up doesn’t remedy the
situation, major mechanical work is the only
solution.
An engine overhaul involves restoring the
internal parts to the specifications of a new
engine. During an overhaul, new piston rings
are fitted and the cylinder walls are
reconditioned (rebored and/or honed). If a
rebore is done by an engineering works, new
oversize pistons will also be fitted. The main
bearings and connecting big-end bearings are
generally renewed and, if necessary, the
crankshaft may be reground to restore the
journals. Generally, the valves are serviced as
well, since they’re usually in less-than-perfect
condition at this point. While the engine is
being overhauled, other components, such as
the distributor, starter and alternator, can be
rebuilt as well. The end result should be a like-
new engine that will give many thousands of
trouble-free miles. Note: Critical cooling
system components such as the hoses,
drivebelts, thermostat and water pump MUST
be renewed when an engine is overhauled.
The radiator should be checked carefully, to
ensure that it isn’t clogged or leaking (see
Chapters 1 or 3). Also, we don’t recommend
overhauling the oil pump - always fit a new
one when an engine is rebuilt.
Before beginning the engine overhaul, read
through the entire procedure to familiarise
yourself with the scope and requirements ofthe job. Overhauling an engine isn’t difficult if
you follow all of the instructions carefully,
have the necessary tools and equipment and
pay close attention to all specifications;
however, it is time consuming. Plan on the
vehicle being tied up for a minimum of two
weeks, especially if parts must be taken to an
automotive machine shop for repair or recon-
ditioning. Check on availability of parts and
make sure that any necessary special tools
and equipment are obtained in advance. Most
work can be done with typical hand tools,
although a number of precision measuring
tools are required for inspecting parts to
determine if they must be replaced. Often an
automotive machine shop will handle the
inspection of parts and offer advice
concerning reconditioning and renewal. Note:
Always wait until the engine has been
completely disassembled and all components,
especially the engine block, have been
inspected before deciding what service and
repair operations must be performed by an
automotive machine shop. Since the block’s
condition will be the major factor to consider
when determining whether to overhaul the
original engine or buy a rebuilt one, never
purchase parts or have machine work done on
other components until the block has been
thoroughly inspected. As a general rule, time
is the primary cost of an overhaul, so it doesn’t
pay to refit worn or substandard parts.
As a final note, to ensure maximum life and
minimum trouble from a rebuilt engine,
everything must be assembled with care, in a
spotlessly-clean environment.
3 Compression check
2
1A compression check will tell you what
mechanical condition the upper end (pistons,
rings, valves, head gaskets) of your engine is
in. Specifically, it can tell you if the
compression is down due to leakage caused
by worn piston rings, defective valves and
seats, or a blown head gasket. Note:The
engine must be at normal operating
temperature, and the battery must be fully-
charged, for this check.
2Begin by cleaning the area around the
spark plugs before you remove them
(compressed air should be used, if available,