water pump BMW 3 SERIES 1985 E30 Workshop Manual

engine damage. Conversely, overfilling the
engine (adding oil above the upper mark) may
cause oil-fouled spark plugs, oil leaks, or oil
seal failures.
6To add oil, remove the filler cap located on
the valve cover (see illustrations). After
adding oil, wait a few minutes to allow the
level to stabilise, then pull the dipstick out and
check the level again. Add more oil if required.
Refit the filler cap, tightening it by hand only.
7Checking the oil level is an important
preventive maintenance step. A consistently
low oil level indicates oil leakage through
damaged seals or defective gaskets, or oil
burning (internal leakage past worn rings or
valve guides). The condition of the oil should
also be noted. If the oil looks milky in colour or
has water droplets in it, the cylinder head
gasket may be blown, or the head or block
may be cracked. The engine should be
repaired immediately. Whenever you check
the oil level, slide your thumb and index finger
up the dipstick before wiping off the oil. If you
see small dirt or metal particles clinging to the
dipstick, the oil should be changed (see
Section 6).
Engine coolant
Warning: Do not allow antifreeze
to come in contact with your
skin, or with the vehiclepaintwork. Rinse off spills immediately
with plenty of water. Antifreeze is highly
toxic if ingested. Never leave antifreeze
lying around in an open container, or in
puddles on the floor; children and pets are
attracted by its sweet smell, and may drink
it. Check with local authorities about
disposing of used antifreeze. Local
collection centres may exist, to see that
antifreeze is disposed of safely.
8All vehicles covered by this manual are
equipped with a pressurised coolant recovery
system. On most models, a white plastic
expansion tank (or coolant reservoir) located
in the engine compartment is connected by a
hose to the radiator. As the engine heats up
during operation, the expanding coolant fills
the tank. As the engine cools, the coolant is
automatically drawn back into the cooling
system, to maintain the correct level.
9The coolant level in the reservoir (see
illustrations)should be checked regularly.
Add a 40%/60% mixture of ethylene glycol-
based antifreeze to water (see illustration).
Warning: Do not remove the
expansion tank cap or radiator
cap to check the coolant level,
unless the engine is completely
cold! The level in the reservoir varies with
the temperature of the engine. When the
engine is cold, the coolant level should beabove the LOW mark on the reservoir.
Once the engine has warmed up, the level
should be at or near the FULL mark. If it
isn’t, allow the engine to cool, then remove
the cap from the reservoir.
10Drive the vehicle and recheck the coolant
level. If only a small amount of coolant is
required to bring the system up to the proper
level, plain water can be used. However,
repeated additions of water will dilute the
antifreeze. In order to maintain the proper
ratio of antifreeze and water, always top-up
the coolant level with the correct mixture.
11If the coolant level drops consistently,
there must be a leak in the system. Inspect
the radiator, hoses, filler cap, drain plugs and
water pump (see Section 29). If no leaks are
noted, have the expansion tank cap or
radiator cap pressure-tested by a BMW
dealer.
12If you have to remove the cap, wait until
the engine has cooled completely, then wrap
a thick cloth around the cap and turn it to the
first stop. If coolant or steam escapes, let the
engine cool down longer, then remove the
cap.
13Check the condition of the coolant as
well. It should be relatively clear. If it’s brown
or rust-coloured, the system should be
drained, flushed and refilled. Even if the
coolant appears to be normal, the corrosion
1•8
4.9d Adding antifreeze mixture4.9c On some 5-Series models, the
expansion tank (coolant reservoir) is
located on the bulkhead4.9b On other models, the expansion tank
(coolant reservoir) is located on the side of
the engine compartment - remove the cap
to add coolant
4.9a On some models, the expansion tank
(coolant reservoir) is mounted on the
radiator - make sure the level is kept at or
near the FULL mark (arrowed)4.6b Topping-up the engine oil4.6a The threaded oil filler cap is located
in the valve cover - always make sure the
area around the opening is clean before
unscrewing the cap
Weekly Checks

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

1 General information
This Part of Chapter 2 is devoted to in-
vehicle engine repair procedures. All
information concerning engine removal and
refitting and engine block and cylinder head
overhaul can be found in Chapter 2B.
The following repair procedures are based
on the assumption that the engine is still fitted
in the vehicle. If the engine has been removed
from the vehicle and mounted on a stand,
many of the steps outlined in this Part of
Chapter 2 will not apply.
The Specifications included in this Part of
Chapter 2 apply only to the procedures
contained in this Part. Chapter 2B contains
the Specifications necessary for cylinder head
and engine block rebuilding.
The single overhead camshaft four- and
six-cylinder engines covered in this manual
are very similar in design. Where there are
differences, they will be pointed out.
The means by which the overhead
camshaft is driven varies according to engine
type; M10 and M30 engines use a timing
chain, while M20 and M40 engines have a
timing belt.
2 Repair operations possible
with the engine in the vehicle
Many major repair operations can be
accomplished without removing the engine
from the vehicle.
Clean the engine compartment and the
exterior of the engine with some type of
degreaser before any work is done. It will
make the job easier, and help keep dirt out of
the internal areas of the engine.
Depending on the components involved, it
may be helpful to remove the bonnet to
improve access to the engine as repairs are
performed (see Chapter 11 if necessary).
Cover the wings to prevent damage to the
paint. Special pads are available, but an old
bedspread or blanket will also work.
If vacuum, exhaust, oil or coolant leaks
develop, indicating a need for gasket or seal
renewal, the repairs can generally be made
with the engine in the vehicle. The intake and
exhaust manifold gaskets, sump gasket,
crankshaft oil seals and cylinder head gasket
are all accessible with the engine in place.
Exterior components, such as the intake
and exhaust manifolds, the sump, the oil
pump, the water pump, the starter motor, the
alternator, the distributor and the fuel system
components, can be removed for repair with
the engine in place.
The cylinder head can be removed without
removing the engine, so this procedure is
covered in this Part of Chapter 2. Camshaft,
rocker arm and valve component servicing ismost easily accomplished with the cylinder
head removed; these procedures are covered
in Part B of this Chapter. Note, however, that
the camshaft on the M40 engine may be
removed with the engine in the vehicle since it
is retained by bearing caps.
In extreme cases caused by a lack of
necessary equipment, repair or renewal of
piston rings, pistons, connecting rods and
big-end bearings is possible with the engine in
the vehicle. However, this practice is not
recommended, because of the cleaning and
preparation work that must be done to the
components involved.
3 Top Dead Centre (TDC) for
No 1 piston- locating
2
Note 1:The following procedure is based on
the assumption that the distributor (if
applicable) is correctly fitted. If you are trying
to locate TDC to refit the distributor correctly,
piston position must be determined by feeling
for compression at the No 1 spark plug hole,
then aligning the ignition timing marks or
inserting the timing tool in the flywheel, as
applicable.
Note 2:The No 1 cylinder is the one closest to
the radiator.
1Top Dead Centre (TDC) is the highest point
in the cylinder that each piston reaches as it
travels up and down when the crankshaft
turns. Each piston reaches TDC on the
compression stroke and again on the exhaust
stroke, but TDC generally refers to piston
position on the compression stroke.
2Positioning the piston at TDC is an essential
part of many procedures, such as timing belt
or chain removal and distributor removal.
3Before beginning this procedure, be sure to
place the transmission in Neutral, and apply
the handbrake or chock the rear wheels. Also,
disable the ignition system by detaching the
coil wire from the centre terminal of the
distributor cap, and earthing it on the engine
block with a jumper wire. Remove the spark
plugs (see Chapter 1).
4In order to bring any piston to TDC, the
crankshaft must be turned using one of the
methods outlined below. When looking at the
front of the engine, normal crankshaft rotation
is clockwise.
(a) The preferred method is to turn the
crankshaft with a socket and ratchet
attached to the bolt threaded into the
front of the crankshaft.
(b) A remote starter switch, which may save
some time, can also be used. Follow the
instructions included with the switch.
Once the piston is close to TDC, use a
socket and ratchet as described in the
previous paragraph.
(c) If an assistant is available to turn the
ignition switch to the Start position in
short bursts, you can get the piston close
to TDC without a remote starter switch.Make sure your assistant is out of the
vehicle, away from the ignition switch,
then use a socket and ratchet as
described in (a) to complete the
procedure.
5Note the position of the terminal for the
No 1 spark plug lead on the distributor cap. If
the terminal isn’t marked, follow the plug lead
from the No 1 cylinder spark plug to the cap
(No 1 cylinder is nearest the radiator).
6Use a felt-tip pen or chalk to make a mark
directly below the No 1 terminal on the
distributor body or timing cover.
7Detach the distributor cap, and set it aside
(see Chapter 1 if necessary).
8Turn the crankshaft (see paragraph 4
above) until the timing marks (located at the
front of the engine) are aligned (see
illustration). The M40 engine does not have
any timing marks at the front of the engine,
but instead has a timing hole in the flywheel
which must be aligned with a hole in the rear
flange of the cylinder block. On this engine,
turn the crankshaft until the distributor rotor is
approaching the No 1 TDC position, then
continue to turn the crankshaft until a suitable
close-fitting drill can be inserted through the
hole in the cylinder block and into the
flywheel.
9Look at the distributor rotor - it should be
pointing directly at the mark you made on the
distributor body or timing cover.
10If the rotor is 180 degrees out, the No 1
piston is at TDC on the exhaust stroke.
11To get the piston to TDC on the
compression stroke, turn the crankshaft one
complete turn (360°) clockwise. The rotor
should now be pointing at the mark on the
distributor or timing cover. When the rotor is
pointing at the No 1 spark plug lead terminal
in the distributor cap and the ignition timing
marks are aligned, the No 1 piston is at TDC
on the compression stroke. Note:If it’s
impossible to align the ignition timing marks
when the rotor is pointing at the mark, the
timing belt or chain may have jumped the
teeth on the sprockets, or may have been
fitted incorrectly.
In-car engine repair procedures 2A•3
3.8 Align the notch in the pulley with the
notch on the timing plate, then check to
see if the distributor rotor is pointing to the
No 1 cylinder (if not, the camshaft is 180
degrees out - the crankshaft will have to
be rotated 360 degrees)
2A

6 Exhaust manifold-
removal and refitting
1
Warning: Make sure the engine is
completely cool before beginning
work on the exhaust system.
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.
2On models where the air cleaner is on the
exhaust manifold side of the engine, remove
the air cleaner housing assembly and/or
airflow sensor to provide sufficient working
area (see Chapter 4, if necessary).
3Unplug the HT leads and set the spark plug
lead harness aside (see Chapter 1).
4Clearly label, then disconnect or remove, all
wires, hoses, fittings, etc. that are in the way.
Be sure to disconnect the oxygen sensor,
where fitted.
5Raise the vehicle, and support it securely
on axle stands. Working from under the
vehicle, separate the exhaust downpipe from
the manifold. Use penetrating oil on the
fasteners to ease removal (see illustrations).
6Remove the axle stands, and lower the
vehicle. Working from the ends of the
manifold toward the centre, loosen the
retaining nuts gradually until they can be
removed. Again, penetrating oil may prove
helpful.
7Pull the manifold off the head, then remove
the old gaskets (see illustrations). Note:Be
very careful not to damage the oxygen sensor,
where fitted.8Clean the gasket mating surfaces of the
head and manifold, and make sure the
threads on the exhaust manifold studs are in
good condition.
9Check for corrosion, warping, cracks, and
other damage. Repair or renew the manifold
as necessary.
10When refitting the manifold, use new
gaskets. Tighten the manifold-to-head
retaining nuts gradually, starting at the centre
and working out to the ends, to the torque
listed in this Chapter’s Specifications. Also
tighten the downpipe-to-manifold nuts.
11The remaining steps are simply a reversal
of the removal procedure.
7 Timing chain covers-
removal and refitting
5
Note 1:This procedure applies to M10 and
M30 engines.
Note 2:The upper timing chain cover can be
removed separately. If you need to remove
both the upper and lower covers, special tools
are required. Read paragraphs 8 and 9 before
beginning work.
Removal
1Disconnect 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.
2If you’re removing the lower timing chain
cover (the upper cover can be removed
separately), remove the cooling fan and fan
shroud, the radiator and the fan drivebelt
pulley (see Chapter 3).
3On the M10 engine only, remove the water
pump (see Chapter 3).
4On engines where the distributor cap is
mounted directly to the timing chain cover,
remove the cap, rotor and the black plastic
cover beneath the rotor (see Chapter 1).
5On the M30 engine fitted with the
L-Jetronic fuel system, remove the
distributor from the upper timing cover (see
Chapter 5).
6Remove the valve cover (see Section 4).
7If you’ll be removing the lower timing chain
cover on the M30 engine, remove the crankshaft
pulley from the vibration damper/hub. Hold the
pulley stationary with a socket on the centre
bolt, and remove the pulley bolts with another
socket (see illustration).
8If you’ll be removing the lower timing chain
2A•6 In-car engine repair procedures
6.7c Removing the exhaust manifold-to-
downpipe gasket (M40 engine)6.7b Removing the exhaust manifold
gasket (M40 engine)6.7a Removing the exhaust manifold
(M40 engine)
6.5b Exhaust manifold-to-downpipe flange
(M40 engine)6.5a Remove the exhaust manifold nuts
(arrowed) from the exhaust pipe (M20
engine) - soaking the nuts with penetrating
oil should make them easier to remove
Remove the windscreen
washer reservoir from the
right-hand side of the engine
compartment to give more
working room.

alignment mark on the camshaft sprocket and
rear timing cover to ensure correct refitting.
6On the M20 engine, loosen the two
tensioner roller retaining bolts a little, and
push the tensioner towards the water pump
(see illustration). With the timing belt tension
relieved, re-tighten the retaining bolt.
7On the M40 engine, loosen the tensioner
retaining nut, and use an Allen key to rotate
the tensioner clockwise. This will relieve the
tension of the timing belt. Tighten the
retaining nut to hold the tensioner in its free
position.
8If the same belt is to be refitted, mark it with
an arrow indicating direction of rotation.
Caution: It is not advisable to
refit a timing belt which has been
removed unless it is virtually
new. On the M40 engine, BMW
recommend that the timing belt is
renewed every time the tensioner roller is
released.
9Remove the timing belt by slipping it off the
roller(s) and the other sprockets (see
illustrations).
10If it’s necessary to remove the camshaft
or the intermediate shaft sprocket, remove the
sprocket bolt while holding the sprocket to
prevent it from moving. To hold the sprocket,
wrap it with a piece of an old timing belt
(toothed side engaging the sprocket teeth) ora piece of leather, then hold the sprocket
using a strap spanner. If a strap spanner is not
available, clamp the ends of the piece of belt
or leather tightly together with a pair of grips.
Before loosening the bolt, make sure you have
the necessary tool for positioning the
camshaft as described in the following
paragraph (see illustration).
Caution: Do not use the timing
belt you’re planning to refit to
hold the sprocket. Also, be sure
to hold the camshaft sprocket
very steady, because if it moves more than
a few degrees, the valves could hit the
pistons.
Note: On the M40 engine, the sprocket is not
directly located on the camshaft with a key, as
the groove in the end of the camshaft allows
the sprocket to move several degrees in either
direction. The retaining bolt locks the sprocket
onto a taper after positioning the camshaft
with a special tool.
11The BMW tool for positioning the camshaft
on the M40 engine consists of a metal plate
which locates over the square lug near the No
1 cylinder lobes on the camshaft - the valve
cover must be removed first (see
illustrations). If the BMW tool cannot be
obtained, a home-made tool should be
fabricated out of metal plate. The tool must be
made to hold the square lug on the camshaft
at right-angles to the upper face of the cylinder
head (ie the contact face of the valve cover).
12If it’s necessary to remove the crankshaft
sprocket, remove the crankshaft hub centre
bolt while holding the crankshaft steady.
Note:The removal of the crankshaft hub
mounting bolt requires a heavy-duty holding
device because of the high torque used to
tighten the bolt. BMW has a special tool,
numbered 112150 (M20 engines) or 112170
(M40 engines), for this purpose. If this tool
cannot be bought or borrowed, check with a
tool dealer or motor factors for a tool capable
of doing the job. Note that the tool number
112170 bolts on the rear of the cylinder head
and engages with the flywheel ring gear, so it
will only be possible to use this tool if the
gearbox has been removed, or if the engine is
out of the vehicle (see illustrations). On
2A•10 In-car engine repair procedures
10.12a Home-made tool for holding the
crankshaft stationary while the crankshaft
pulley bolt is being loosened (engine
removed for clarity)
10.11b The BMW camshaft-holding tool in
position on the M40 engine10.11a The BMW tool for holding the
camshaft in the TDC position on
M40 engines
10.10 Removing the camshaft sprocket on
the M40 engine
10.9b Removing the timing belt from the
camshaft sprocket on the M40 engine
10.9a When removing the timing belt on
models with a two-piece crankshaft hub,
it’s a tight fit to remove it around the hub,
but it’s a lot easier than removing the
crankshaft hub assembly, which is secured
by a very tight bolt10.6 Loosen the idler pulley bolts
(arrowed) to relieve the tension on the
timing belt so it can be removed

nothing (including oil, water, etc) remains in
the holes (see illustration).
25BMW recommend head bolts are renewed,
but if the old ones are re-used, mount each bolt
in a vice, and run a die down the threads to
remove corrosion and restore the threads. Dirt,
corrosion, sealant and damaged threads will
affect torque readings (see illustration). If the
bolts or their threads are damaged, do not re-
use the bolts - fit a new set.
26Refit any components removed from the
head prior to cleaning and inspection. On the
M40 engine, locate a new rubber O-ring in the
groove in the top of the oil pump/front end
cover housing (see illustration).
27Make sure the gasket sealing surfaces ofthe engine block and cylinder head are clean
and oil-free. Lay the head gasket in place on
the block, with the manufacturer’s stamped
mark facing up (it usually says “UP,” “OBEN”
or something similar). Use the dowel pins in the
top of the block to properly locate the gasket.
28Carefully set the cylinder head in place
on the block. Use the dowel pins to properly
align it. Where the engine is tilted slightly (ie
M40 engine) you may find it helpful to fit
guide studs to ensure correct positioning of
the cylinder head on the block. Use two old
head bolts, one screwed into each end of
the block. Cut the heads off the bolts, and
use a hacksaw to cut slots in the tops
of the bolts so they can be removed oncethe cylinder head is in position (see
illustration).
29Fit the cylinder head bolts (see
illustration).
30Tighten the cylinder head bolts, in the
sequence shown, to the torque listed in this
Chapter’s Specifications (see illustrations).
Note that on some engines the final stage of
tightening takes place after the engine has
been run.
31The remainder of refitting is the reverse of
removal. Set the valve clearances on M10,
M20 and M30 engines (see Chapter 1) before
refitting the valve cover (check them again
after the engine is warmed-up). Run the
engine and check for leaks.
2A•14 In-car engine repair procedures
12.30d Cylinder head bolt TIGHTENING
sequence for M40 (four-cylinder) engines12.30c Cylinder head bolt TIGHTENING
sequence for M30 (six-cylinder) engines12.30b Cylinder head bolt TIGHTENING
sequence for M20 (six-cylinder) engines
12.30a Cylinder head bolt TIGHTENING
sequence for M10 (four-cylinder) engines12.29 Inserting a cylinder head bolt
(M40 engine)12.28 Lowering the cylinder head onto the
block (M40 engine)
12.26 Fitting a new rubber O-ring in the
groove in the top of the oil pump/front end
cover on the M40 engine12.25 A die should be used to remove
sealant and corrosion from the head bolt
threads prior to installation12.24 The cylinder head bolt holes should
be cleaned and restored with a tap (be
sure to remove debris from the holes after
this is done)

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,

detach them. Pieces of masking tape with
numbers or letters written on them work well
(see illustration).
6Label and detach all coolant hoses from the
engine (see Chapter 3).
7Remove the cooling fan, shroud and
radiator (see Chapter 3). Note:On the M40
engine, it is only necessary to remove the
cooling fan and shroud; however, prevent
damage to the radiator by covering it with a
piece of wood or cardboard.
8Remove the drivebelts (see Chapter 1).
9Disconnect the fuel lines from the fuel rail
(see Chapter 4).
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, and 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.
10Disconnect the accelerator cable (see
Chapter 4) and kickdown linkage/speed
control cable (see Chapter 7B), if applicable,
from the engine.
11Where fitted, unbolt the power steering
pump (see Chapter 10). Leave the lines/hoses
attached, and make sure the pump is kept in
an upright position in the engine compartment
(use wire or rope to restrain it out of the way).
12On air-conditioned models, unbolt the
compressor (see Chapter 3) and set it aside,
or tie it up out of the way. Do not disconnect
the hoses.
13Drain the engine oil (see Chapter 1) and
remove the filter. Remove the engine splash
guard from under the engine.
14Remove the starter motor (see Chapter 5).15Remove the alternator (see Chapter 5).
This is not essential on all models, but it is a
good idea in any case to avoid accidental
damage.
16Unbolt the exhaust system from the
engine (see Chapter 4).
17If you’re working on a vehicle with an
automatic transmission, remove the torque
converter-to-driveplate fasteners (see
Chapter 7B). On the M40 engine, unbolt the
automatic transmission fluid coolant pipes
from the sump.
18Support the transmission with a jack.
Position a block of wood between them, to
prevent damage to the transmission. Special
transmission jacks with safety chains are
available - use one if possible.
19Attach an engine sling or a length of chain
to the lifting brackets on the engine. If the
brackets have been removed, the chain can
be bolted directly to the intake manifold studs,
but place a flat washer between the chain and
the nut, and tighten the nut all the way up to
the chain, to avoid the possibility of the studs
bending.
20Roll the hoist into position and connect
the sling to it. Take up the slack in the sling or
chain, but don’t lift the engine.
Warning: DO NOT place any part
of your body under the engine
when it’s supported only by a
hoist or other lifting device.
21On M10, M20 and M30 engines, remove
the transmission rear crossmember, and
slightly lower the rear of the transmission.
22Remove the transmission-to-engine block
bolts using a Torx socket. Note:The bolts
holding the bellhousing to the engine block
will require a swivel at the socket, and a very
long extension going back towards the
transmission.
23Remove the engine mounting-to-frame
bracket nuts. On the M40 engine, unbolt the
dampers from the mountings.
24Recheck to be sure nothing is still
connecting the engine to the transmission or
vehicle. Disconnect anything still remaining.
25Raise the engine slightly. Carefully work it
forwards to separate it from the transmission.
If you’re working on a vehicle with an
automatic transmission, you may find the
torque converter comes forward with theengine. If it stays with the transmission, leave
it, but you may find it easier to let it come
forward until it can be grasped easier and be
pulled from the crankshaft. Note:When
refitting the torque converter to the
transmission before the engine is refitted, be
sure to renew the transmission front pump
seal, which will probably be damaged when
the converter comes out with the engine.
Either method is acceptable, but be prepared
for some fluid to leak from the torque
converter if it comes out of the transmission. If
you’re working on a vehicle with a manual
transmission, draw the engine forwards until
the input shaft is completely disengaged from
the clutch. Slowly raise the engine out of the
engine compartment. Check carefully to make
sure everything is disconnected.
26Remove the flywheel/driveplate (and
where applicable, the engine rear plate), and
mount the engine on an engine stand (see
illustration). Do not turn the M40 engine
upside-down (see Cautionin Section 4).
Refitting
27Check the engine and transmission
mountings. If they’re worn or damaged, renew
them.
28Refit the flywheel or driveplate (see
Chapter 2A). If you’re working on a manual
transmission vehicle, refit the clutch and
pressure plate (see Chapter 7A). Now is a
good time to fit a new clutch.
29If the torque converter came out with the
engine during removal, carefully refit the
converter into the transmission before the
engine is lowered into the vehicle.
30Carefully lower the engine into the engine
compartment - make sure the engine
mountings line up.
31If you’re working on an automatic
transmission vehicle, guide the torque
converter onto the crankshaft following the
procedure outlined in Chapter 7B.
32If you’re working on a manual
transmission vehicle, apply a dab of high-
melting-point grease to the input shaft, and
guide it into the clutch and crankshaft pilot
bearing until the bellhousing is flush with the
engine block.. Do not allow the weight of the
engine to hang on the input shaft.
33Refit the transmission-to-engine bolts,
and tighten them securely.
Caution: DO NOT use the bolts to
force the transmission and
engine together.
34Refit the remaining components in the
reverse order of removal.
35Add coolant, oil, power steering and
transmission fluid as needed.
2B•6 General engine overhaul procedures
5.26 Removing the engine rear plate -
M40 engine5.5 Label each wire before unplugging the
connector
If there’s any possibility of
confusion, make a sketch of
the engine compartment and
clearly label the lines, hoses
and wires.
It may be necessary to rock
the engine slightly, or to turn
the crankshaft, to allow the
input shaft splines to mate
with the clutch plate

36Run the engine and check for leaks and
proper operation of all accessories, then refit
the bonnet and test drive the vehicle.
37Where necessary, have the air
conditioning system recharged and leak-
tested.
6 Engine overhaul- alternatives
The do-it-yourselfer is faced with a number
of options when performing an engine
overhaul. The decision to renew the engine
block, piston/connecting rod assemblies and
crankshaft depends on a number of factors,
with the number one consideration being the
condition of the block. Other considerations
are cost, access to machine shop facilities,
parts availability, time required to complete
the project, and the extent of prior mechanical
experience on the part of the do-it-yourselfer.
Some of the alternatives include:
Individual parts - If the inspection
procedures reveal that the engine block and
most engine components are in re-usable
condition, purchasing individual parts may be
the most economical alternative. The block,
crankshaft and piston/connecting rod
assemblies should all be inspected carefully.
Even if the block shows little wear, the
cylinder bores should be surface-honed.
Crankshaft kit- A crankshaft kit (where
available) consists of a reground crankshaft
with matched undersize new main and
connecting big-end bearings. Sometimes,
reconditioned connecting rods and new
pistons and rings are included with the kit
(such a kit is sometimes called an “engine
kit”). If the block is in good condition, but the
crankshaft journals are scored or worn, a
crankshaft kit and other individual parts may
be the most economical alternative.
Short block- A short block consists of an
engine block with a crankshaft and
piston/connecting rod assemblies already
fitted. New bearings are fitted, and all
clearances will be correct. The existing
camshaft, valve train components, cylinder
head and external parts can be bolted to the
short block with little or no machine shop
work necessary.
Full block - A “full” or “complete” block
consists of a short block plus an oil pump,
sump, cylinder head, valve cover, camshaft
and valve train components, timing sprockets
and chain (or belt) and timing cover. All
components are fitted with new bearings,
seals and gaskets used throughout. The
refitting of manifolds and external parts is all
that’s necessary.
Give careful thought to which alternative is
best for you, and discuss the situation with
local machine shops, parts dealers and
experienced rebuilders before ordering or
purchasing new parts.
7 Engine overhaul-
dismantling sequence
1It’s much easier to dismantle and work on
the engine if it’s mounted on a portable
engine stand. A stand can often be hired quite
cheaply from a tool hire shop. Before the
engine is mounted on a stand, the
flywheel/driveplate should be removed from
the engine.
2If a stand isn’t available, it’s possible to
dismantle the engine with it blocked up on the
floor. Be extra-careful not to tip or drop the
engine when working without a stand.
3If you’re going to obtain a rebuilt engine, all
the external components listed below must
come off first, to be transferred to the new
engine if applicable. This is also the case if
you’re doing a complete engine overhaul
yourself. Note:When removing the external
components from the engine, pay close
attention to details that may be helpful or
important during refitting. Note the fitted
position of gaskets, seals, spacers, pins,
brackets, washers, bolts and other small items.
Alternator and brackets
Emissions control components
Distributor, HT leads and spark plugs
Thermostat and housing cover
Water pump
Fuel injection/carburettor and fuel system
components
Intake and exhaust manifolds
Oil filter and oil pressure sending unit
Engine mounting brackets (see illustration)
Clutch and flywheel/driveplate
Engine rear plate (where applicable)
4If you’re obtaining a short block, which
consists of the engine block, crankshaft,
pistons and connecting rods all assembled,
then the cylinder head, sump and oil pump
will have to be removed as well. See Section 6
for additional information regarding the
different possibilities to be considered.
5If you’re planning a complete overhaul, the
engine must be dismantled and the internal
components removed in the following general
order:
Valve cover
Intake and exhaust manifolds
Timing belt or chain covers
Timing chain/belt
Water pump
Cylinder head
Sump
Oil pump
Piston/connecting rod assemblies
Crankshaft and main bearings
Camshaft
Rocker shafts and rocker arms (M10, M20
and M30 engines)
Cam followers and hydraulic tappets
(M40 engine)
Valve spring retainers and springs
Valves
6Before beginning the dismantling andoverhaul procedures, make sure the following
items are available. Also, refer to Section 21
for a list of tools and materials needed for
engine reassembly.
Common hand tools
Small cardboard boxes or plastic bags for
storing parts
Compartment-type metal box for storing
the hydraulic tappets (M40 engine)
Gasket scraper
Ridge reamer
Vibration damper puller
Micrometers
Telescoping gauges
Dial indicator set
Valve spring compressor
Cylinder surfacing hone
Piston ring groove cleaning tool
Electric drill motor
Tap and die set
Wire brushes
Oil gallery brushes
Cleaning solvent
8 Cylinder head- dismantling
4
1Remove the cylinder head (see Chapter 2A).
2Remove the oil supply tube from its
mounting on top of the cylinder head (see
illustrations). Note:It’s important to renew
the seals under the tube mounting bolts.
General engine overhaul procedures 2B•7
7.3 Engine left-hand mounting bracket -
M40 engine
8.2a Remove the oil tube from the top of
the cylinder head (M10 engine). Be sure to
note the location of all gaskets and
washers for reassembly
2B

5Gently tap the caps with a soft-faced
hammer, then separate them from the engine
block. If necessary, use the bolts as levers to
remove the caps. Try not to drop the bearing
shells if they come out with the caps.
6Carefully lift the crankshaft out of the
engine. It may be a good idea to have an
assistant available, since the crankshaft is
quite heavy (see illustration). With the
bearing shells in place in the engine block and
main bearing caps, return the caps to their
respective locations on the engine block, and
tighten the bolts finger-tight.
14 Intermediate shaft-
removal and inspection
5
Note:The intermediate shaft is used on the
M20 engine only. The shaft rotates in the
engine block parallel to the crankshaft. It is
driven by the timing belt, and its only purpose
is to drive the oil pump.
1Remove the timing belt (see Chapter 2A).
2With the belt removed, unbolt the gear from
the intermediate shaft and unbolt the front
cover.
3Remove the oil pump driveshaft (see
Chapter 2A).
4The shaft is held in the cylinder block by a
retaining plate with two bolts. Remove the
bolts, and pull the shaft forwards and out of
the block.
5Look for any signs of abnormal wear on the
bearing surfaces or the gear at the back end
of the shaft, which drives the oil pump shaft. If
the bearing surfaces in the engine block show
wear, they’ll have to be attended to by a
machine shop.
15 Engine block- cleaning
2
Caution: The core plugs may be
difficult or impossible to retrieve
if they’re driven into the block
coolant passages.
1Remove the core plugs from the engine
block. To do this, knock one side of each plug
into the block with a hammer and punch,
grasp the other side by its edge with large
pliers, and pull it out.
2Using a gasket scraper, remove all traces of
gasket material from the engine block. Be very
careful not to nick or gouge the gasket sealing
surfaces.
3Remove the main bearing caps, and
separate the bearing shells from the caps and
the engine block. Tag the bearings, indicating
which cylinder they were removed from and
whether they were in the cap or the block,
then set them aside.
4Remove all of the threaded oil gallery plugs
from the block. The plugs are usually very
tight - they may have to be drilled out and theholes retapped. Use new plugs when the
engine is reassembled.
5If the engine is extremely dirty, it should be
taken to a machine shop to be steam-
cleaned.
6After the block is returned, clean all oil
holes and oil galleries one more time. Brushes
specifically designed for this purpose are
available at most motor factors. Flush the
passages with warm water until the water runs
clear, dry the block thoroughly, and wipe all
machined surfaces with a light, rust-
preventive oil. If you have access to
compressed air, use it to speed the drying
process and to blow out all the oil holes and
galleries.
Warning: Wear eye protection
when using compressed air!
7If the block isn’t extremely dirty or sludged
up, you can do an adequate cleaning job with
hot soapy water and a stiff brush. Take plenty
of time, and do a thorough job. Regardless of
the cleaning method used, be sure to clean all
oil holes and galleries very thoroughly, dry the
block completely, and coat all machined
surfaces with light oil.
8The threaded holes in the block must be
clean to ensure accurate torque readingsduring reassembly. Run the proper-size tap
into each of the holes to remove rust,
corrosion, thread sealant or sludge, and to
restore damaged threads (see illustration). If
possible, use compressed air to clear the
holes of debris produced by this operation. Be
sure also that the holes are dry- any oil or
other fluid present could cause the block to
be cracked by hydraulic pressure when the
bolts are tightened. Now is a good time to
clean the threads on all bolts. Note that BMW
recommend that the cylinder head bolts and
main bearing bolts are renewed as a matter of
course.
9Refit the main bearing caps, and tighten the
bolts finger-tight.
10After coating the sealing surfaces of the
new core plugs with a suitable sealant, refit
them in the engine block (see illustration).
Make sure they’re driven in straight and
seated properly, or leakage could result.
Special tools are available for this purpose,
but a large socket, with an outside diameter
that will just slip into the core plug, a 1/2-inch
drive extension, and a hammer, will work just
as well.
11Apply non-hardening sealant to the new
oil gallery plugs, and thread them into the
holes in the block. Make sure they’re
tightened securely.
12If the engine isn’t going to be
reassembled right away, cover it with a large
plastic bag to keep it clean.
2B•14 General engine overhaul procedures
15.10 A large socket on an extension can
be used to drive the new core plugs into
the block
15.8 All bolt holes in the block -
particularly the main bearing cap and head
bolt holes - should be cleaned and
restored with a tap (be sure to remove
debris from the holes after this is done)
13.6 Remove the crankshaft by lifting
straight up. Be very careful when removing
the crankshaft - it is very heavy13.4 Use a centre-punch or number-
stamping dies to mark the main bearing
caps to ensure refitting in their original
locations on the block (make the punch
marks near one of the bolt heads)