timing belt BMW 3 SERIES 1985 E30 User Guide

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

models with a two-piece hub, after removing
the outer hub piece, you’ll then need to
remove the sprocket with a bolt-type puller
(available at most motor factors). When using
the puller, thread the crankshaft centre bolt in
approximately three turns, and use this as a
bearing point for the puller’s centre bolt.
Inspection
13Check for a cracked, worn or damaged
belt. Renew it if any of these conditions are
found (see illustrations). Also look at the
sprockets for any signs of irregular wear or
damage, indicating the need for renewal.
Note:If any parts are to be renewed, check
with your local BMW dealer parts department
to be sure compatible parts are used. On M20
engines, later sprockets, tensioner rollers and
timing belts are marked “Z 127”. Renewal of
the timing belt on M20 engines will mean that
the later belt tensioner should also be fitted, if
not already done.
14Inspect the idler roller and, on M20
engines, the tension spring. Rotate the
tensioner roller to be sure it rotates freely, with
no noise or play. Note:When fitting a new
timing belt, it is recommended that a new
tensioner be fitted also.
Refitting
15On the M20 engine, refit the idler/
tensioner/spring so that the timing belt can be
fitted loosely.
16Refit the sprockets using a reversal of the
removal procedure; tighten the retaining bolts
to the specified torque. On the M40 engine,
turn the camshaft sprocket clockwise as far
as possible within the location groove, then
tighten the retaining bolt to an initial torque of
1 to 3 Nm at this stage.
17If you are refitting the old belt, make sure
the mark made to indicate belt direction of
rotation is pointing the right way (the belt
should rotate in a clockwise direction as you
face the front of the engine).
18Refit the timing belt, placing the belt
under the crankshaft sprocket first to get bythe housing. Guide the belt around the other
sprocket(s).
19Finally, place the belt over the
idler/tensioner rollers.
20On the M20 engine, loosen the tensioner
bolts and allow the spring tension to be
applied to the belt.
21On the M20 engine, lightly apply pressure
behind the tensioner to be sure spring
pressure is being applied to the belt (see
illustration). Don’t tighten the bolts while
applying pressure; lightly tighten the bolts
only after releasing the tensioner.
22On the M40 engine, unbolt and remove
the valve cover, then use the special tool to
hold the camshaft in the TDC position (see
paragraph 11).
23On the M40 engine, loosen the tensioner
roller retaining nut, and use an Allen key to
rotate the roller anti-clockwise until the timing
belt is tensioned correctly. The 90°-twist
method of checking the tension of the timing
belt is not accurate enough for this engine,
and it is strongly recommended that the
special BMW tensioning tool is obtained if at
all possible (apply 32 ±2 graduations on the
tool) (see illustration). A reasonably accurate
alternative can be made using an Allen key
and a spring balance (see illustration).Make
sure that the spring balance is positioned as
shown, since the tensioner roller is on an
eccentric, and different readings will be
obtained otherwise. The spring balance
should be connected 85 mm along the Allen
key, and a force of 2.0 kg (4.4 lb) should be
In-car engine repair procedures 2A•11
10.13a Inspect the timing belt carefully for
cracking, as shown here. . .
10.13b . . . and any other damage
10.12c Removing the crankshaft sprocket
from the front of the crankshaft10.12b Removing the crankshaft pulley
bolt (M40 engine)
10.23b Using a spring balance and Allen
key to adjust the tension of the timing belt
on the M40 engine
Dimension A = 85 mm
10.23a Using the special BMW tool to
check the tension of the timing belt on the
M40 engine
10.21 On the M20 engine, after the belt
has been installed correctly around all
sprockets and the tensioner pulley, lightly
apply pressure to the tensioner, to be sure
the tensioner isn’t stuck and has full
movement against the timing belt
2A

applied. Tighten the retaining nut to the
specified torque to hold the tensioner in its
correct position. Note:It is important that the
timing belt is tensioned correctly. If the belt is
over-tightened, it will howl, and there is the
possibility of it being damaged. If the belt is
too slack, it may jump on the sprockets.
24Check to make sure the camshaft and
crankshaft timing marks are still aligned(see
illustrations 10.5a and 10.5b).
25Turn the crankshaft clockwise through
two complete revolutions. (Remove the
camshaft positioning tool from the M40
engine first.)
Caution: This is necessary to
stretch the new belt. If not done,
the belt tensioner will be too
loose, and damage could result.
26On the M20 engine, loosen the tensioner
roller bolts, then tighten them to the torque
listed in this Chapter’s Specifications.
27On the M40 engine, loosen the tensioner
roller retaining nut, and re-adjust the tension
of the timing belt as described in paragraph
23. On completion, tighten the tensioner roller
retaining nut, then fully tighten the camshaft
sprocket bolt if previously loosened (see
illustration).
28Verify that the timing marks are still
perfectly aligned. If not, remove and refit the
timing belt.
29The remainder of refitting is the reverse of
removal.
11 Front oil seals- renewal
5
Note:Oil seals are fitted with their sealing lips
facing inwards (towards the engine).
M10 and M30 (timing chain)
engines
Camshaft front seal (M30 engines
only)
1Remove the upper timing chain cover only
(see Section 7).2Support the cover on two blocks of wood,
and drive out the seal from behind with a
hammer and screwdriver. Be very careful not
to damage the seal bore in the process.
3Coat the outside diameter and lip of the
new seal with multi-purpose grease, and drive
the seal into the cover with a hammer and a
socket slightly smaller in diameter than the
outside diameter of the seal.
4The remainder of refitting is the reverse of
removal.
Crankshaft front seal (M10 and
M30 engines)
5Remove the crankshaft pulley and vibration
damper (see Section 7).
6Carefully prise the old seal out of the cover
with a large screwdriver. Be very careful not to
damage the seal bore or the crankshaft with
the tool. Wrap the tip of the screwdriver with a
piece of tape to prevent damage.
7Clean the bore in the cover, and coat the
outer edge of the new seal with engine oil or
multi-purpose grease. Also lubricate the lips
of the seal with multi-purpose grease. Using a
socket with an outside diameter slightly
smaller than the outside diameter of the seal,
carefully drive the new seal into place with a
hammer (see illustration). If a socket isn’t
available, a short section of large-diameter
pipe will work. Check the seal after refitting to
be sure the spring around the inside of the
seal lip didn’t pop out of place.
8The remainder of refitting is the reverse of
removal.
M20 and M40 (timing belt)
engines
Camshaft front seal (M20 and
M40 engines)
9Remove the timing belt and camshaft
sprocket (see Section 10).
10On the M20 engine only, remove the two
screws, and separate the camshaft seal
housing from the cylinder head by pulling it as
you rotate it back and forth.
11On the M20 engine only, support the
housing on two blocks of wood, and drive the
seal out of the housing from behind using ahammer and screwdriver. Be very careful not
to damage the seal housing.
12On the M40 engine, prise the seal out
from the cylinder head using a screwdriver,
being careful not to damage the camshaft
surface or the seal bore.
13Coat the lip and outside diameter of the
new seal with multi-purpose grease.
14On the M40 engine, wrap some adhesive
tape around the end of the camshaft to
protect the new seal from the location groove
as it is being fitted (see illustration).
15Carefully locate the new seal in position,
and press it in by hand initially so that it enters
the bore. Drive the new seal into the housing
or cylinder head (as applicable) using a
hammer and a socket with a diameter slightly
smaller than the outside diameter of the seal.
On the M40 engine, remove the adhesive tape
from the end of the camshaft.
16On the M20 engine, renew the O-ring on
the back of the seal housing, and work the lip
of the seal over the end of the camshaft. Refit
the screws and tighten them securely.
17The remainder of refitting is the reverse of
removal.
Crankshaft and intermediate shaft
front seals (M20 engines)
18Remove the timing belt and crankshaft
and intermediate shaft pulleys as applicable
(see Section 10). Note:We recommend the
timing belt be renewed any time it is removed.
19Remove the bolts and nuts securing the
front cover to the engine block. Be sure to
remove the three bolts from underneath that
connect the front of the sump to the bottom of
the front cover (see illustration 7.14).
20Run a sharp, thin knife between the sump
gasket and the front cover, cutting the cover
free from the gasket. Be very careful not to
damage the gasket, and keep it clean so you
can re-use it.
21Break the front cover-to-block gasket seal
by tapping the cover with a rubber mallet or
block of wood and hammer. Do not prise
between the cover and the engine block, as
damage to the gasket sealing surfaces will
result.
2A•12 In-car engine repair procedures
11.14 Fitting a new camshaft oil seal on
the M40 engine (note the adhesive tape
around the end of the camshaft to protect
the seal)11.7 The crankshaft front oil seal is
pressed into the front of the lower timing
chain cover (cover removed from the
engine for clarity)10.27 Tightening the camshaft sprocket
retaining bolt on the M40 engine

22Using a scraper, remove all traces of old
gasket material from the sealing surfaces of
the covers and engine block.
Caution: Be very careful not to
scratch or gouge the delicate
aluminium surfaces. Also, do not
damage the sump gasket, and
keep it clean. Gasket removal solvents are
available at motor factors, and may
prove helpful. After all gasket material has
been removed, the gasket surfaces
can be degreased by wiping them
with a rag dampened with a suitable
solvent.
23Support the cover on two blocks of wood,
and drive out the seals from behind with a
hammer and screwdriver. Be very careful not
to damage the seal bores in the process.
24Coat the outside diameters and lips of the
new seals with multi-purpose grease, and
drive the seals into the cover with a hammer
and a socket slightly smaller in diameter than
the outside diameter of the seal.
25Apply a film of RTV-type gasket sealant to
the surface of the sump gasket that mates
with the front cover. Apply extra beads of RTV
sealant to the edges where the gasket meets
the engine block. Note:If the sump gasket is
damaged, instead of fitting a whole new
gasket, you might try trimming the front
portion of the gasket off at the point where it
meets the engine block, then trim off the front
portion of a new sump gasket so it’s exactly
the same size. Cover the exposed inside area
of the sump with a rag, then clean all traces of
old gasket material off the area where the
gasket was removed. Attach the new gasket
piece to the sump with contact-cement-type
gasket adhesive, then apply RTV-type sealant
as described at the beginning of this
paragraph.
26Coat both sides of the new gasket with
RTV-type gasket sealant, then attach the front
cover to the front of the engine, carefully
working the seals over the crankshaft and
intermediate shaft. Refit the bolts and tighten
them evenly to the torque listed in this
Chapter’s Specifications. Work from bolt-to-
bolt in a criss-cross pattern, to be sure they’re
tightened evenly.Note 1:Tighten the front
cover-to-block bolts first, then tighten the
sump-to-cover bolts. Note 2:After applying
RTV-type sealant, reassembly must be
completed in about 10 minutes so the RTV
won’t prematurely harden.
27The remainder of refitting is the reverse of
removal.
Crankshaft front seal (M40 engines)
28Remove the timing belt and crankshaft
sprocket (see Section 10).
29Remove the Woodruff key from the
groove in the end of the crankshaft.
30Note the fitted position of the oil seal, then
prise it out from the front cover using a
screwdriver, but take care not to damage the
bore of the cover or the surface of thecrankshaft. If the seal is tight, drill two small
holes in the metal end of the seal, and use two
self-tapping screws to pull out the seal. Make
sure all remains of swarf are removed.
31Coat the outside diameter and lip of the
new seal with multi-purpose grease, then
drive it into the cover with a hammer and a
socket slightly smaller in diameter than the
outside diameter of the seal. Make sure the
seal enters squarely.
32The remainder of refitting is the reverse of
removal. Note that it is recommended that the
timing belt be renewed - see Section 10.
12 Cylinder head-
removal and refitting
5
Removal
1Relieve the fuel pressure on all fuel injection
engines (see Chapter 4).
2Disconnect the negative cable from the
battery. Where the battery is located in the
engine compartment, the battery may be
removed completely (see Chapter 5).
Caution: If the radio in your
vehicle is equipped with an anti-
theft system, make sure you
have the correct activation code
before disconnecting the battery.
Note: If, after connecting the battery, the
wrong language appears on the instrument
panel display, refer to page 0-7 for the
language resetting procedure.
3Remove the air cleaner assembly (see
Chapter 4).
4Disconnect the wiring from the distributor
(mark all wiring for position first, if necessary),
and the HT lead from the coil (see Chapter 5).
5Disconnect the lead from the coolant
temperature sender unit (see Chapter 3).
6Disconnect the fuel lines from the fuel rail or
carburettor as applicable (see Chapter 4).
7Drain the cooling system (see Chapter 3).
8Clearly label then disconnect all other
hoses from the throttle body, intake manifold,
carburettor and cylinder head, as applicable.
9Disconnect the throttle cable from the
throttle linkage or carburettor (see Chapter 4).
10Disconnect the exhaust manifold from the
cylinder head (see Section 6). Depending on
the engine type, It may not be necessary to
disconnect the manifold from the exhaust
pipe; however, on right-hand-drive models,
the steering column intermediate shaft may
not allow the manifold to clear the studs on
the cylinder head.
11Remove or disconnect any remaining
hoses or lines from the intake manifold,
including the ignition advance vacuum line(s),
and the coolant and heater hoses.
12On early carburettor models, disconnect
the wiring from the alternator and starter
motor.13Remove the intake manifold (see Sec-
tion 5). Do not dismantle or remove any fuel
injection system components unless it is
absolutely necessary.
14Remove the fan drivebelt and fan (see
Chapter 3).
15Remove the valve cover and gasket (see
Section 4). Remove the semi-circular rubber
seal from the front of the cylinder head, where
this is not incorporated in the valve cover
gasket.
16Set No 1 piston at Top Dead Centre on
the compression stroke (see Section 3).
17Remove the timing chain or belt (see
Section 8 or 10). Note:If you want to save
time by not removing and refitting the timing
belt or chain and re-timing the engine, you can
unfasten the camshaft sprocket and suspend
it out of the way - with the belt or chain still
attached - by a piece of rope. Be sure the
rope keeps firm tension on the belt or chain,
so it won’t become disengaged from any of
the sprockets.
18Loosen the cylinder head bolts a quarter-
turn at a time each, in the reverse of the
tightening sequence shown (see illustrations
12.30a, 12.30b, 12.30c or 12.30d). Do
notdismantle or remove the rocker arm
assembly at this time on M10, M20 and M30
engines.
19Remove the cylinder head by lifting it
straight up and off the engine block. Do not
prise between the cylinder head and the
engine block, as damage to the gasket sealing
surfaces may result. Instead, use a blunt bar
positioned in an intake port to gently prise the
head loose.
20Remove any remaining external
components from the head to allow for
thorough cleaning and inspection. See
Chapter 2B for cylinder head servicing
procedures. On the M40 engine, remove the
rubber O-ring from the groove in the top of the
oil pump/front end cover housing.
Refitting
21The mating surfaces of the cylinder head
and block must be perfectly clean when the
head is refitted.
22Use a gasket scraper to remove all traces
of carbon and old gasket material, then clean
the mating surfaces with a suitable solvent. If
there’s oil on the mating surfaces when the
head is refitted, the gasket may not seal
correctly, and leaks could develop. When
working on the block, stuff the cylinders with
clean rags to keep out debris. Use a vacuum
cleaner to remove material that falls into the
cylinders.
23Check the block and head mating
surfaces for nicks, deep scratches and other
damage. If the damage is slight, it can be
removed with a file; if it’s excessive,
machining may be the only alternative.
24Use a tap of the correct size to chase the
threads in the head bolt holes, then clean the
holes with compressed air - make sure that
In-car engine repair procedures 2A•13
2A

15The remainder of refitting is the reverse of
removal. Fit a new gasket to the lower sump
section on models with the M40 engine.
16On completion refill the engine with oil
(Chapter 1). Run the engine and check that
there are no oil leaks from the sump gasket or
other disturbed components.
14 Oil pump- removal,
inspection and refitting
5
Removal
1Remove the sump (see Section 13).
M10, M20 and M30 engines
2On M10 and M30 engines, remove the
three bolts that attach the gear to the front of
the pump (see illustration). Note: Some
models have a single centre nut attaching the
gear to the oil pump.
3Unbolt the oil pump from the engine block
(see illustrations)and remove it.
4On the M20 engine, the intermediate shaft
drives the oil pump driveshaft, which drives
the oil pump. To remove the driveshaft,
remove the hold-down plate from the block,
and lift out the plug. Check the condition of
the O-ring, and renew it if necessary. Lift the
driveshaft out and check both gears for wear,
renewing them if worn or damaged (see
illustration).
5If the gear on the intermediate shaft is worn,
or the intermediate shaft bearing is worn or
damaged, the intermediate shaft must be
removed. Remove the engine (see Chap-
ter 2B), then remove the timing belt,
crankshaft and intermediate shaft sprockets
(see Section 10) and the engine front cover
(see Section 11). The intermediate shaft can
be slid out the front of the engine.
M40 engines
6Remove the timing belt as described in
Section 10.
7Remove the cylinder head as described in
Section 12.
8Unscrew the nut and remove the timing belt
tensioner from the front end cover (see
illustration). If necessary, unscrew the stud
from the cylinder block.9Unscrew and remove the crankshaft hub
bolt while holding the crankshaft stationary.
The bolt is tightened to a very high torque,
and it will be necessary to prevent the
crankshaft turning. Ideally, a metal bar should
be bolted to the sprocket, or the starter motor
may be removed and the flywheel held using a
wide-bladed screwdriver. Beware of possible
damage to surrounding components if it is
necessary to improvise some method of
immobilising the crankshaft.
10Remove the sprocket and spacer, noting
that the shoulder on the spacer faces inwards.
11Unscrew the bolts and remove the
stabilising and guide rollers from the front end
cover (see illustrations).12Using a small screwdriver or similar
instrument, remove the key from the groove in
the nose of the crankshaft (see illustration).
13Pull the spacer ring off the crankshaft (see
illustration).
14Unscrew the remaining bolts, and remove
the front end cover and oil pump from the
cylinder block. Note the locations of the front
cover bolts, as they are of different sizes. With
the cover removed, extract the rubber O-ring
from the groove in the nose of the crankshaft
(see illustrations).
15Note the fitted location of the oil seal, then
prise it out of the housing.
2A•16 In-car engine repair procedures
14.11b Removing the guide roller from the
front end cover (M40 engine)14.11a Removing the stabilising roller
from the front end cover (M40 engine)14.8 Removing the timing belt tensioner
(M40 engine)
14.3b On M10 and M30 engines, the oil
pump is bolted to the front and centre of
the engine block14.4 If necessary on the M20 engine,
remove the plug and oil pump driveshaft
from the engine. Inspect the driveshaft
gear, as well as this intermediate shaft
gear in the engine block (arrowed)
14.3a On M20 engines, the oil pump is
bolted across the engine block from side
to side, towards the front of the engine14.2 On M10 and M30 engines, remove the
three bolts that hold the driven gear to the
oil pump, and remove the gear

26Refit the cover plate and tighten the bolts
to the specified torque.
27To check the pressure relief valve, extract
the circlip and remove the sleeve, spring and
piston. Check that the length of the spring is
as given in the Specifications (see
illustrations). Reassemble the pressure relief
valve using a reversal of the dismantling
procedure.
Refitting
M10, M20 and M30 engines
28Make sure the mounting surfaces are
clean, then insert the pump into the engine
block recess. Refit the bolts and tighten them
to the torque specified at the beginning of this
Chapter.
29Refitting is the reverse of removal.
M40 engines
30Clean the mating surfaces, then refit the
front end cover and oil pump to the cylinder
block, together with a new gasket (see
illustration). Tighten the bolts to the
specified torque. Note that there are two sizes
of bolts, and they have different torque
settings.
31Fit the spacer ring on the front of the
crankshaft.
32Apply engine oil to the lips of the new oil
seal, then press it into the housing to its
previously-noted position. To ensure the oil
seal enters the housing squarely, use a large
socket and the crankshaft pulley bolt to pull it
into position (see illustration).
33Refit the key to the groove in the nose of
the crankshaft.34Refit the stabilising roller to the front end
cover, and tighten the bolt.
35Refit the sprocket, spacer and crankshaft
pulley bolt. Tighten the bolt to the specified
torque while holding the crankshaft stationary
using one of the methods previously
described.
36Refit the timing belt tensioning roller, but
do not tighten the bolt at this stage.
37Refit the cylinder head as described in
Section 12.
38Refit the timing belt as described in
Section 10.
39Refit the sump (see Section 13).
15 Flywheel/driveplate-
removal and refitting
3
1Remove the transmission (on vehicles with
manual transmission, see Chapter 7A; on
vehicles with automatic transmission, see
Chapter 7B).
2On vehicles with manual transmission,
remove the clutch (see Chapter 8).
3Where necessary, mark the relationship of
the flywheel/driveplate to the crankshaft, so it
can be refitted the same way.
4The flywheel/driveplate is attached to the
rear of the crankshaft with eight bolts. Loosen
and remove the bolts, then separate it from
2A•18 In-car engine repair procedures
14.32 Using a large socket and the
crankshaft pulley bolt to pull the oil seal
into the housing (M40 engine)14.30 Locating a new gasket on the front
of the cylinder block (M40 engine)14.27e Checking the length of the
pressure relief valve spring (M40 engine)
14.27d . . . and piston14.27c . . . spring . . .
14.27b . . . and remove the sleeve . . .14.27a Extract the circlip from the oil
pump (M40 engine) . . .14.24b Measuring the clearance between
the oil pump outer and inner rotors
(M40 engine)

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

6If coarse grinding compound is being used,
work only until a dull, matt even surface is
produced on both the valve seat and the
valve, then wipe off the used compound and
repeat the process with fine compound. When
a smooth, unbroken ring of light grey matt
finish is produced on both the valve and seat,
the grinding operation is complete. Do not
grind in the valves any further than absolutely
necessary.
7When all the valves have been ground-in,
carefully wash off all traces of grinding
compound using paraffin or a suitable solvent
before reassembly of the cylinder head.
11 Cylinder head- reassembly
5
1Make sure the cylinder head is spotlessly-
clean before beginning reassembly.
2If the head was sent out for valve servicing,
the valves and related components will
already be in place. Begin the reassembly
procedure with paragraph 8.
3Starting at one end of the head, applymolybdenum disulphide (“moly”) grease or
clean engine oil to each valve stem, and refit
the first valve.
4Lubricate the lip of the valve guide seal,
carefully slide it over the tip of the valve, then
slide it all the way down the stem to the guide.
Using a hammer and a deep socket or seal-
fitting tool, gently tap the seal into place until
it’s completely seated on the guide (see
illustrations). Don’t twist or distort a seal
during fitting, or it won’t seal properly against
the valve stem. Note:On some engines, the
seals for intake and exhaust valves are
different - don’t mix them up.
5Drop the spring seat or shim(s) over the
valve guide, and set the valve spring and
retainer in place.
6Compress the spring with a valve spring
compressor and carefully refit the collets in
the upper groove, then slowly release the
compressor and make sure the collets seat
properly (see illustration).
7Repeat paragraphs 3 to 6 for each of the
valves. Be sure to return the components to
their original locations - don’t mix them up!
M10, M20 and M30 engines
8Refit the rocker arms and shafts by
reversing the dismantling sequence. Be sure
to refit the rocker shafts in the correct
orientation. The guide plate notches and the
small oil holes face inwards; the large oil holes
face down, toward the valve guides.
9Lubricate the camshaft journals and lobes(see illustration), then carefully insert it into
the cylinder head, rotating it as you go so the
camshaft lobes will clear the rocker arms. It
will also be necessary to compress the rocker
arms against the valve springs, as described
in Section 8, so they’ll clear the camshaft
lobes. Be very careful not to scratch or gouge
the camshaft bearing surfaces in the cylinder
head.
M40 engines
10Lubricate the bores for the hydraulic
tappets in the cylinder head, then insert the
tappets in their original positions.
11Locate the thrust discs and cam followers
on the valves and pivot posts in their original
positions.
12Lubricate the bearing surfaces of the
camshaft in the cylinder head.
13Locate the camshaft in the cylinder head
so that the valves of No 1 cylinder are both
open, and the valves of No 4 cylinder are
“rocking” (exhaust closing and inlet opening).
No 1 cylinder is at the timing belt end.
14Lubricate the bearing surfaces in the
bearing caps, then locate them in their correct
positions and insert the retaining bolts.
Progressively tighten the bolts to the specified
torque.
15Fit a new oil seal to the camshaft front
bearing cap (see Chapter 2A, Section 11).
All engines
16Refit the oil supply tube to the top of the
cylinder head together with new seals, then
tighten the bolts to the specified torque.
17The cylinder head may now be refitted
(see Chapter 2A).
12 Pistons/connecting rods-
removal
5
Note:Before removing the piston/connecting
rod assemblies, remove the cylinder head and
the sump. On M10, M20 and M30 engines
only, remove the oil pump. Refer to the
appropriate Sections in Chapter 2A.
1Use your fingernail to feel if a ridge has
formed at the upper limit of ring travel (about
6 mm down from the top of each cylinder). If
2B•12 General engine overhaul procedures
11.9 Lubricate the camshaft bearing
journals and lobes with engine assembly
paste or molybdenum disulphide (“moly”)
grease
11.6 With the retainer fitted, compress the
valve spring and refit the collets as shown 11.4b . . .then lightly drive on the seal with
a socket or piece of tubing11.4a Lubricate the valve guide seal, and
place it on the guide (the valve should be
in place too) . . .
A light spring placed under
the valve head will greatly
ease the valve grinding
operation.
Apply a small dab of grease to each
collet to hold it in place, if necessary.

carbon deposits or cylinder wear have
produced ridges, they must be completely
removed with a special tool called a ridge
reamer (see illustration). Follow the
manufacturer’s instructions provided with the
tool. Failure to remove the ridges before
attempting to remove the piston/connecting
rod assemblies may result in piston ring
breakage.
2After the cylinder ridges have been
removed, turn the engine upside-down so the
crankshaft is facing up.
3Before the connecting rods are removed,
check the side play with feeler gauges. Slide
them between the first connecting rod and
crankshaft web until no play is apparent (see
illustration). The side play is equal to the
thickness of the feeler gauge(s). If the side
play exceeds the service limit, new
connecting rods will be required. If new rods
(or a new crankshaft) are fitted, ensure that
some side play is retained (if not, the rods will
have to be machined to restore it - consult a
machine shop for advice if necessary). Repeat
the procedure for the remaining connecting
rods.
4Check the connecting rods and caps for
identification marks. If they aren’t plainly
marked, use a small centre-punch to make
the appropriate number of indentations (see
illustration)on each rod and cap (1, 2, 3, etc.,
depending on the cylinder they’re associated
with).
5Loosen each of the connecting rod cap
nuts/bolts a half-turn at a time until they can
be removed by hand. Remove the No 1
connecting rod cap and bearing shell. Don’t
drop the bearing shell out of the cap.
6Where applicable, slip a short length of
plastic or rubber hose over each connecting
rod cap stud to protect the crankshaft journal
and cylinder wall as the piston is removed
(see illustration).
7Remove the bearing shell, and push the
connecting rod/piston assembly out through
the top of the engine. Use a wooden hammer
handle to push on the upper bearing surface
in the connecting rod. If resistance is felt,
double-check to make sure that all of the
ridge was removed from the cylinder.8Repeat the procedure for the remaining
cylinders.
9After removal, reassemble the connecting
rod caps and bearing shells in their respective
connecting rods, and refit the cap nuts/bolts
finger-tight. Leaving the old bearing shells in
place until reassembly will help prevent the
connecting big-end bearing surfaces from
being accidentally nicked or gouged.
10Don’t separate the pistons from the
connecting rods (see Section 18).
13 Crankshaft- removal
5
Note: The crankshaft can be removed only
after the engine has been removed from the
vehicle. It’s assumed that the flywheel or
driveplate, vibration damper, timing chain or
belt, sump, oil pump and piston/connecting
rod assemblies have already been removed.
The rear main oil seal housing must be
unbolted and separated from the block before
proceeding with crankshaft removal.
1Before the crankshaft is removed, check
the endfloat. Mount a dial indicator with the
stem in line with the crankshaft and touching
the nose of the crankshaft, or one of its webs
(see illustration).
2Push the crankshaft all the way to the rear,and zero the dial indicator. Next, prise the
crankshaft to the front as far as possible, and
check the reading on the dial indicator. The
distance that it moves is the endfloat. If it’s
greater than the maximum endfloat listed in
this Chapter’s Specifications, check the
crankshaft thrust surfaces for wear. If no wear
is evident, new main bearings should correct
the endfloat.
3If a dial indicator isn’t available, feeler
gauges can be used. Identify the main bearing
with the thrust flanges either side of it - this is
referred to as the “thrust” main bearing (see
Section 24, paragraph 6). Gently prise or push
the crankshaft all the way to the front of the
engine. Slip feeler gauges between the
crankshaft and the front face of the thrust
main bearing to determine the clearance.
4Check the main bearing caps to see if
they’re marked to indicate their locations.
They should be numbered consecutively from
the front of the engine to the rear. If they
aren’t, mark them with number-stamping dies
or a centre-punch (see illustration). Main
bearing caps generally have a cast-in arrow,
which points to the front of the engine.
Loosen the main bearing cap bolts a quarter-
turn at a time each, working from the outer
ends towards the centre, until they can be
removed by hand. Note if any stud bolts are
used, and make sure they’re returned to their
original locations when the crankshaft is
refitted.
General engine overhaul procedures 2B•13
12.4 Mark the big-end bearing caps in
order from the front of the engine to the
rear (one mark for the front cap, two for
the second one and so on)12.3 Check the connecting rod side play
with a feeler gauge as shown12.1 A ridge reamer is required to remove
the ridge from the top of each cylinder - do
this before removing the pistons!
13.1 Checking crankshaft endfloat with a
dial indicator
12.6 To prevent damage to the crankshaft
journals and cylinder walls, slip sections of
rubber or plastic hose over the rod bolts
before removing the pistons
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)