pump BMW 3 SERIES 1983 E30 User Guide

8 Timing chain and
sprockets- removal,
inspection and refitting
5
Note:This procedure applies to M10 and M30
engines.
Caution: Once the engine is set
at TDC, do not rotate the
camshaft or crankshaft until the
timing chain is reinstalled. If the
crankshaft or camshaft is rotated with the
timing chain removed, the valves could hit
the pistons, causing expensive internal
engine damage.
Removal
1Position the No 1 cylinder at Top Dead
Centre (TDC) on the compression stroke (see
Section 3).
2Remove the valve cover (see Section 4).
Double-check that the No 1 cylinder is at TDC
on the compression stroke by making sure the
No 1 cylinder rocker arms are loose (not
compressing their valve springs).
3Remove the upper timing chain cover (see
Section 7). Note the location of the camshaft
timing marks, which should now be aligned.
On four-cylinder (M10) engines, there’s
usually a stamped line on the camshaft flange
that aligns with a cast mark on the top of the
cylinder head; also, the camshaft sprocket
dowel pin hole will be at its lowest point. On
six-cylinder (M30) engines, a line drawn
through two of the camshaft sprocket bolts
opposite each other would be exactly vertical,
while a line drawn through the other two bolts
would be horizontal. Additionally, the locating
pin should be in the lower left corner (between
the 7 and 8 o’clock positions). Be sure you’ve
identified the correct camshaft TDC position
before dismantling, because correct valve
timing depends on you aligning them exactly
on reassembly. Note:As the engine is
mounted in the engine compartment at anangle, all references to horizontal and vertical
whilst timing the camshafts are in relation to
the crankshaft, and not the ground.
4Hold the crankshaft stationary with a socket
and ratchet on the vibration damper centre bolt,
then loosen (but don’t unscrew completely) the
four bolts attaching the camshaft sprocket to
the camshaft. Be very careful not to rotate the
camshaft or crankshaft. Note:Some earlier
models may have locking tabs for the camshaft
sprocket bolts. Bend the tabs down before
loosening the bolts. The tabs are no longer
available from the manufacturer, and do not
have to be used on refitting.
5Remove the lower timing chain cover (see
Section 7).
6Unscrew and remove the four camshaft
sprocket bolts, then disengage the chain from
the crankshaft sprocket and carefully remove
the chain and camshaft sprocket from the
engine. It may be necessary to gently prise
the camshaft sprocket loose from the
camshaft with a screwdriver.
Inspection
Timing sprockets
7Examine the teeth on both the crankshaft
sprocket and the camshaft sprocket for wear.
Each tooth forms an inverted V. If worn, the
side of each tooth under tension will be
slightly concave in shape when compared
with the other side of the tooth (i.e. one side of
the inverted V will be concave when
compared with the other, giving the teeth a
hooked appearance). If the teeth appear to be
worn, the sprockets must be renewed. Note:
The crankshaft sprocket is a press fit on the
crankshaft, and can be removed with a jaw-
type puller after the Woodruff key and oil
pump are removed (see Section 14). However,
BMW recommends the new sprocket be
pressed onto the crankshaft after being
heated to 80°C (175°F) on the M10 engine, or
to 200°C(390°F) on the M30 engine. For this
reason, if the crankshaft sprocket requires
renewal, we recommend removing the
crankshaft (see Part B of this Chapter) and
taking it to an engineering works to have the
old sprocket pressed off and a new one
pressed on.
Timing chain
8The chain should be renewed if the
sprockets are worn or if the chain is loose
(indicated by excessive noise in operation).
It’s a good idea to renew the chain anyway if
the engine is stripped down for overhaul. The
rollers on a very badly worn chain may be
slightly grooved. To avoid future problems, if
there’s any doubt at all about the chain’s
condition, renew it.
Chain rail and tensioner
9Inspect the chain guide rail and tensioner
rail for deep grooves caused by chain contact.
Renew them if they are excessively worn. The
rails can be renewed after removing the
circlips with a pointed tool or needle-nose
pliers (see illustration).10Shake the tensioner plunger, and listen for
a rattling sound from the check ball. If you
can’t hear the ball rattling, renew the plunger.
11To further check the tensioner plunger,
blow through it first from the closed end, then
from the slotted (guide) end. No air should
flow through the plunger when you blow
through the closed end, and air should flow
through it freely when you blow through the
slotted end. If the tensioner fails either test,
renew it.
Refitting
12Refit the tensioner rail and chain guide
rail, if removed.
13Temporarily refit the lower timing chain
cover and vibration damper, so you can check
the crankshaft timing marks. Once you’ve
verified the TDC marks are aligned, remove
the damper and cover.
14Loop the timing chain over the crankshaft
sprocket, then loop it over the camshaft
sprocket and, guiding the chain between the
chain guide and tensioner rail, refit the
camshaft sprocket on the camshaft. Make
sure the camshaft timing marks are aligned.
15The remainder of refitting is the reverse of
removal. Be sure to tighten the fasteners to
the correct torques (see this Chapter’s Speci-
fications).
9 Timing belt covers-
removal and refitting
2
Note:This procedure applies to M20 and M40
engines.
Caution: If the radio in your
vehicle is equipped with an anti-
theft system, make sure you
have the correct activation code
before disconnecting the battery.
Note: If, after connecting the battery, the
wrong language appears on the instrument
panel display, refer to page 0-7 for the
language resetting procedure.
1Disconnect the battery negative cable.
2Remove the fan clutch and fan shroud (see
Chapter 3).
3On the M20 engine, remove the radiator
(see Chapter 3).
4Remove the fan drivebelt pulley.
2A•8 In-car engine repair procedures
9.6a Unbolt the distributor cap
(M40 engine) . . .
8.9 To remove the tensioner or chain guide
rail, remove the circlips with a pointed tool
or needle-nose pliers - the circlips tend to
fly off when they’re released, so make sure
you catch them or they’ll get lost (or,
worse, wind up in the engine!)

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

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

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)

13 Sump- removal and refitting
1
1Drain the engine oil (see Chapter 1).
2Raise the front of the vehicle and place it
securely on axle stands.
3Remove the splash shields from under the
engine.
4Where applicable, disconnect the hoses
attached to the sump, and move them to one
side (see illustration).
5Where applicable, disconnect the oil level
sensor electrical connector (see illustration).
6Where applicable, remove the cast-
aluminium inspection cover that covers the
rear of the sump (see illustrations).
7On models with the M40 engine, unbolt and
remove the lower sump section and remove
the gasket (this is necessary for access to the
front mounting bolts). Unscrew the mounting
bolt, and pull the oil dipstick tube from the
sump (see illustrations). Check the condition
of the O-ring, and renew it if necessary.
8On models with the M40 engine, unscrew
the engine mounting nuts on both sides, then
attach a suitable hoist and lift the engine
sufficiently to allow the sump to be removed.
As a safety precaution, position axle stands or
blocks of wood beneath the engine.
9Remove the bolts securing the sump to theengine block and front/rear covers (see
illustration).
10Tap on the sump with a soft-faced
hammer to break the gasket seal, and lower
the sump from the engine.
11Using a gasket scraper, scrape off all
traces of the old gasket from the engine
block, the timing chain cover, the rear main oil
seal housing, and the sump. Be especially
careful not to nick or gouge the gasket sealing
surfaces of the timing chain cover and the oil
seal housing (they are made of aluminium,
and are quite soft).
12Clean the sump with solvent, and dry it
thoroughly. Check the gasket sealing surfaces
for distortion. Clean any residue from thegasket sealing surfaces on the sump and
engine with a rag dampened with a suitable
solvent.
13Before refitting the sump, apply a little
RTV-type gasket sealant to the area where the
front and rear covers join the cylinder block..
Lay a new sump gasket in place on the block.
If necessary, apply more sealant to hold the
gasket in place.
14Carefully position the sump in place (do
not disturb the gasket) and refit the bolts.
Start with the bolts closest to the centre of the
sump, and tighten them to the torque listed in
this Chapter’s Specifications, using a criss-
cross pattern. Do not overtighten them, or
leakage may occur.
In-car engine repair procedures 2A•15
13.5 If applicable, disconnect the oil level
sensor connector at the left side of the
engine, down near the power steering
pump mounting bracket13.4 If applicable, remove the nut securing
the power steering lines to the sump, and
move the lines to one side to allow you to
get at the sump bolts12.30e Angle-tightening the cylinder head
bolts (M40 engine)
13.9 Remove the bolts holding the sump
to the engine block and front cover, as
shown here on a six-cylinder engine13.7b Removing the oil dipstick tube
bracket mounting bolt
13.6b . . . remove the cover to get to all
the sump bolts13.6a Remove the four inspection cover
bolts (arrowed) and . . .
13.7a Main sump retaining bolts accessed
after removal of the lower sump section on
the M40 engine (engine on bench for clarity)
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

Inspection
Note:Considering that a malfunctioning oil
pump can easily cause major engine damage,
we recommend that the oil pump should
always be renewed during engine overhaul,
unless it’s in as-new condition.
M10, M20 and M30 engines
16Remove the cover and check the pump
body, gears or rotors and cover for cracks
and wear (especially in the gear or rotor
contact areas).
17Check the strainer to make sure it is not
clogged or damaged.
18Lubricate the gears with clean engine oil,
then attach the pump cover to the body and
tighten the bolts evenly and securely.19Before refitting the pump - new, rebuilt or
original - on the engine, check it for proper
operation. Fill a clean container to a depth of
one inch with fresh engine oil of the
recommended viscosity.
20Immerse the oil pump inlet in the oil, and
turn the driveshaft anti-clockwise by hand. As
the shaft is turned, oil should be discharged
from the pump outlet.M40 engines
21With the front end cover on the bench,
unscrew the bolts and remove the cover plate
to expose the oil pump rotors (see
illustrations).
22Identify the rotors for position, then
remove them from the housing (see
illustrations).23Clean the housing and the rotors
thoroughly, then refit the rotors, making sure
that they are in their previously-noted
positions. The inner rotor must be fitted with
the guide facing the body.
24Using feeler blades, measure the
clearance between the oil pump body and the
outer rotor, then check the clearance
between the outer and inner rotors (see
illustrations).
25If the clearance is not as given in the
Specifications, the complete oil pump and
front end cover should be renewed. If the
clearance is within tolerance, remove the
rotors, then pour a little engine oil into the
housing. Refit the rotors and turn them to
spread the oil around.
In-car engine repair procedures 2A•17
14.14a Front end cover and oil pump in
position on the front of the M40 engine14.13 Removing the spacer ring from the
front of the crankshaft14.12 Removing the key from the groove
in the nose of the crankshaft (M40 engine)
14.24a Measuring the clearance between
the oil pump body and the outer rotor
(M40 engine)14.22b . . . and outer rotor from the oil
pump (M40 engine)14.22a Removing the inner rotor . . .
14.21b . . . and remove the oil pump cover
(M40 engine)14.21a Unscrew the bolts . . .14.14b Extract the rubber O-ring from the
groove in the nose of the crankshaft
(M40 engine)
2A

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)

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,

otherwise a small brush or even a bicycle tyre
pump will work). The idea is to prevent dirt
from getting into the cylinders as the
compression check is being done.
3Remove all the spark plugs from the engine
(see Chapter 1).
4Block the throttle wide open, or have an
assistant hold the throttle pedal down.
5On carburettor models, disconnect the LT
lead from the coil. On fuel injection models,
disable the fuel pump and ignition circuit by
removing the main relay(see illustration).
This is to avoid the possibility of a fire from
fuel being sprayed in the engine
compartment. The location of the main relay is
generally near the fuse panel area under the
bonnet, but refer to Chapter 12 for the
specific location on your model.
6Fit the compression gauge in the No 1
spark plug hole (No 1 cylinder is nearest the
radiator).
7Turn the engine on the starter motor over at
least seven compression strokes, and watch
the gauge. The compression should build up
quickly in a healthy engine. Low compression
on the first stroke, followed by gradually-
increasing pressure on successive strokes,
indicates worn piston rings. A low
compression reading on the first stroke, which
doesn’t build up during successive strokes,
indicates leaking valves or a blown head
gasket (a cracked head could also be the
cause). Deposits on the undersides of the
valve heads can also cause low compression.
Record the highest gauge reading obtained.
8Repeat the procedure for the remaining
cylinders, and compare the results to the
compression listed in this Chapter’s Specifi-
cations.
9If compression was low, add some engine
oil (about three squirts from a plunger-type oil
can) to each cylinder, through the spark plug
hole, and repeat the test.
10If the compression increases after the oil
is added, the piston rings are definitely worn.
If the compression doesn’t increasesignificantly, the leakage is occurring at the
valves or head gasket. Leakage past the
valves may be caused by burned valve seats
and/or faces or warped, cracked or bent
valves.
11If two adjacent cylinders have equally low
compression, there’s a strong possibility that
the head gasket between them is blown. The
appearance of coolant in the combustion
chambers or the crankcase would verify this
condition.
12If one cylinder is 20 percent lower than the
others, and the engine has a slightly rough
idle, a worn exhaust lobe on the camshaft
could be the cause.
13If the compression is unusually high, the
combustion chambers are probably coated
with carbon deposits. If that’s the case, the
cylinder head should be removed and
decarbonised.
14If compression is way down, or varies
greatly between cylinders, it would be a good
idea to have a leak-down test performed by a
garage. This test will pinpoint exactly
where the leakage is occurring and how
severe it is.
4 Engine removal-
methods and precautions
If you’ve decided that an engine must be
removed for overhaul or major repair work,
several preliminary steps should be taken.
Locating a suitable place to work is
extremely important. Adequate work space,
along with storage space for the vehicle, will
be needed. If a workshop or garage isn’t
available, at the very least a flat, level, clean
work surface made of concrete or asphalt is
required.
Cleaning the engine compartment and
engine before beginning the removal
procedure will help keep tools clean and
organised.
An engine hoist or A-frame will also be
necessary. Make sure the equipment is rated
in excess of the combined weight of the
engine and accessories. Safety is of primary
importance, considering the potential hazards
involved in lifting the engine out of the vehicle.
If the engine is being removed by a novice,
a helper should be available. Advice and aid
from someone more experienced would also
be helpful. There are many instances when
one person cannot simultaneously perform all
of the operations required when lifting the
engine out of the vehicle.
Plan the operation ahead of time. Arrange
for or obtain all the tools and equipment you’ll
need prior to beginning the job. Some of the
equipment necessary to perform engine
removal and refitting safely and with relative
ease are (in addition to an engine hoist) a
heavy-duty trolley jack, complete sets of
spanners and sockets as described in thefront of this manual, wooden blocks, and
plenty of rags and cleaning solvent for
mopping up spilled oil, coolant and fuel. If the
hoist must be hired, make sure that you
arrange for it in advance, and perform all of
the operations possible without it beforehand.
This will save you money and time.
Plan for the vehicle to be out of use for
quite a while. A machine shop will be required
to perform some of the work which the do-it-
yourselfer can’t accomplish without special
equipment. These establishments often have
a busy schedule, so it would be a good idea
to consult them before removing the engine,
in order to accurately estimate the amount of
time required to rebuild or repair components
that may need work.
Always be extremely careful when removing
and refitting the engine. Serious injury can
result from careless actions. Plan ahead, take
your time and a job of this nature, although
major, can be accomplished successfully.
Warning: The air conditioning
system is under high pressure.
Do not loosen any fittings or
remove any components until
after the system has been discharged by a
qualified engineer. Always wear eye
protection when disconnecting air
conditioning system fittings.
Caution: If removing the M40
engine, it is important not to turn
the engine upside-down for
longer than 10 minutes since it is
possible for the oil to drain out of the
hydraulic tappets. This would render the
tappets unserviceable, and damage could
possibly occur to the engine when it is
next started up.
5 Engine- removal and refitting
3
Caution: If the radio in your
vehicle is equipped with an anti-
theft system, make sure you
have the correct activation code before
disconnecting the battery.
Note: If, after connecting the battery, the
wrong language appears on the instrument
panel display, refer to page 0-7 for the
language resetting procedure.
Removal1Relieve the fuel system pressure (see
Chapter 4), then disconnect the negative
cable from the battery.
2Cover the wings and front panel, and
remove the bonnet (see Chapter 11). Special
pads are available to protect the wings, but an
old bedspread or blanket will also work.
3Remove the air cleaner housing and intake
ducts (see Chapter 4).
4Drain the cooling system (see Chapter 1).
5Label the vacuum lines, emissions system
hoses, wiring connectors, earth straps and
fuel lines, to ensure correct refitting, then
General engine overhaul procedures 2B•5
3.5 As a safety precaution, before
performing a compression check, remove
the cover and the main relay (arrowed)
from the left side of the engine
compartment to disable the fuel and
ignition systems (525i model shown, other
models similar)
2B