1985 BMW 3 SERIES Idle

2A
General
Displacement
3-series, E30 body style
316i (1988 to 1991) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1596 cc (M40/4-cylinder engine)
316 (1983 to 1988) and 318i (1983 to 1987) . . . . . . . . . . . . . . . . 1766 cc (M10/4-cylinder engine)
318i (1987 1991) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1796 cc (M40/4-cylinder engine)
320i (1987 to 1991) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1990 cc (M20/6-cylinder engine)
325i (1987 to 1991) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2494 cc (M20/6-cylinder engine)
5-series, E28 body style (“old-shape”)
518 (1981 to 1985) and 518i (1985 to 1988) . . . . . . . . . . . . . . . . 1766 cc (M10/4-cylinder engine)
525i (1981 to 1988) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2494 cc (M30/6-cylinder engine)
528i (1981 to 1988) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2788 cc (M30/6-cylinder engine)
535i (1985 to 1988) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3430 cc (M30/6-cylinder engine)
M535i (1985 to 1988) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3430 cc (M30/6-cylinder engine)
5-series, E34 body style (“new-shape”)
518i (1990 to 1993) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1796 cc (M40/4-cylinder engine)
520i (1988 to 1991) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1990 cc (M20/6-cylinder engine)
525i (1988 to 1991) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2494 cc (M20/6-cylinder engine)
530i (1988 to 1991) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2986 cc (M30/6-cylinder engine)
535i (1988 to 1993) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3430 cc (M30/6-cylinder engine)
Firing order
Four-cylinder engine . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-3-4-2
Six-cylinder engine . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-5-3-6-2-4
Lubrication system
Oil pressure (all engines)
At idle . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0.5 to 2.0 bars
Running (for example, at 4000 rpm) . . . . . . . . . . . . . . . . . . . . . . . . . . 4 bars or above (typically)
Oil pump rotor clearance - M40 engine
(body-to-outer rotor/outer rotor-to-inner rotor) . . . . . . . . . . . . . . . . . . . 0.12 mm to 0.20 mm
Oil pump pressure relief valve spring length - M40 engine . . . . . . . . . . 84.1 mm
Chapter 2 Part A:
In-car engine repair procedures
Camshaft - removal, inspection and refitting . . . . . . See Chapter 2B
Compression check . . . . . . . . . . . . . . . . . . . . . . . . . See Chapter 2B
Crankshaft rear oil seal - renewal . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
Cylinder head - removal and refitting . . . . . . . . . . . . . . . . . . . . . . . . 12
Cylinder head - dismantling and inspection . . . . . . . See Chapter 2B
Drivebelt check, adjustment and renewal . . . . . . . . See Chapter 1
Engine - removal and refitting . . . . . . . . . . . . . . . . . See Chapter 2B
Engine mountings - check and renewal . . . . . . . . . . . . . . . . . . . . . . 17
Engine oil and filter change . . . . . . . . . . . . . . . . . . . See Chapter 1
Engine overhaul - general information . . . . . . . . . . . See Chapter 2B
Exhaust manifold - removal and refitting . . . . . . . . . . . . . . . . . . . . . 6
Flywheel/driveplate - removal and refitting . . . . . . . . . . . . . . . . . . . 15
Front oil seals - renewal . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
General information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
Intake manifold - removal and refitting . . . . . . . . . . . . . . . . . . . . . . . 5Oil pump - removal, inspection and refitting . . . . . . . . . . . . . . . . . . 14
Repair operations possible with the engine in the vehicle . . . . . . . . 2
Rocker arm and shaft assembly - dismantling, inspection
and reassembly . . . . . . . . . . . . . . . . . . . . . . . . . . . See Chapter 2B
Spark plug renewal . . . . . . . . . . . . . . . . . . . . . . . . . . See Chapter 1
Sump - removal and refitting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
Timing belt and sprockets - removal, inspection and refitting . . . . . 10
Timing belt covers - removal and refitting . . . . . . . . . . . . . . . . . . . . . 9
Timing chain and sprockets - removal, inspection and refitting . . . . 8
Timing chain covers - removal and refitting . . . . . . . . . . . . . . . . . . . 7
Top Dead Centre (TDC) for No 1 piston - locating . . . . . . . . . . . . . . 3
Valve clearance check and adjustment . . . . . . . . . . . See Chapter 1
Valve cover - removal and refitting . . . . . . . . . . . . . . . . . . . . . . . . . . 4
Valves - servicing . . . . . . . . . . . . . . . . . . . . . . . . . . . See Chapter 2B
2A•1
Easy,suitable for
novice with little
experienceFairly easy,suitable
for beginner with
some experienceFairly difficult,
suitable for competent
DIY mechanic
Difficult,suitable for
experienced DIY
mechanicVery difficult,
suitable for expert
DIY or professional
Degrees of difficulty
Specifications Contents

12After the No 1 piston has been positioned
at TDC on the compression stroke, TDC for
any of the remaining pistons can be located
by turning the crankshaft and following the
firing order. Mark the remaining spark plug
lead terminal locations just like you did for the
No 1 terminal, then number the marks to
correspond with the cylinder numbers. As you
turn the crankshaft, the rotor will also turn.
When it’s pointing directly at one of the marks
on the distributor, the piston for that particular
cylinder is at TDC on the compression stroke.
4 Valve cover-
removal and refitting
1
Caution: If the radio in your
vehicle is equipped with an anti-
theft system, make sure you
have the correct activation code
before disconnecting the battery.
Note: If, after connecting the battery, the
wrong language appears on the instrument
panel display, refer to page 0-7 for the
language resetting procedure.
Removal
1Disconnect the battery negative cable.
2Detach the breather hose from the valve
cover.
3On M20 engines, unbolt and remove the
intake manifold support bracket and, if
applicable, the bracket for the engine sensors
or idle air stabiliser (it will probably be
necessary to disconnect the electrical
connectors from the sensors and stabiliser).
4On M30 engines, disconnect the electrical
connector for the airflow sensor. Unclip the
electrical harness, moving it out of the way.
5Where necessary on M30 engines, remove
the hoses and fittings from the intake air hose,
then loosen the clamp and separate the hose
from the throttle body. Unscrew the mounting
nuts for the air cleaner housing, and remove
the housing together with the air hose and
airflow sensor.
6Remove the valve cover retaining nuts and
washers (see illustrations). Where necessary,
disconnect the spark plug lead clip or coverfrom the stud(s), and set it aside. It will usually
not be necessary to disconnect the leads from
the spark plugs.
7Remove the valve cover and gasket.
Discard the old gasket. On the M40 engine,
also remove the camshaft cover (see
illustrations). If applicable, remove the semi-
circular rubber seal from the cut-out at the
front of the cylinder head.
Refitting
8Using a scraper, remove all traces of old
gasket material from the sealing surfaces of
the valve cover and cylinder head.
Caution: Be very careful not to
scratch or gouge the delicate
aluminium surfaces. Gasket
removal solvents are available at
motor factors, and may prove helpful.
After all gasket material has been
removed, the gasket surfaces can be
degreased by wiping them with a rag
dampened with a suitable solvent.
9If applicable, place a new semi-circular
rubber seal in the cut-out at the front of the
cylinder head, then apply RTV-type gasket
sealant to the joints between the seal and the
mating surface for the valve cover gasket.
Note:After the sealant is applied, you should
refit the valve cover and tighten the nuts within
ten minutes.
10Refit the camshaft cover (M40 engine), the
valve cover and a new gasket. Refit the
washers and nuts; tighten the nuts evenly and
securely. Don’t overtighten these nuts - theyshould be tight enough to prevent oil from
leaking past the gasket, but not so tight that
they warp the valve cover.
11The remainder of refitting is the reverse of
removal.
5 Intake manifold-
removal and refitting
2
Removal
1Allow the engine to cool completely, then
relieve the fuel pressure on fuel-injection
engines (see Chapter 4).
2Disconnect the battery negative cable.
Caution: If the radio in your
vehicle is equipped with an anti-
theft system, make sure you
have the correct activation code
before disconnecting the battery.
Note: If, after connecting the battery, the
wrong language appears on the instrument
panel display, refer to page 0-7 for the
language resetting procedure.
3Drain the engine coolant (see Chapter 1)
below the level of the intake manifold. If the
coolant is in good condition, it can be saved
and reused.
4On fuel injection engines, loosen the hose
clamp and disconnect the large air inlet hose
from the throttle body. It may also be
necessary to remove the entire air
cleaner/inlet hose assembly to provide
enough working room (see Chapter 4).
2A•4 In-car engine repair procedures
4.7b Removing the camshaft cover on the
M40 engine4.7a Removing the valve cover on the
M40 engine4.7c Removing the valve cover gasket on
the M40 engine
4.6b Valve cover bolt locations (arrowed)
on M20 six-cylinder engines4.6a Valve cover bolt locations (arrowed)
on M10 four-cylinder engines

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

2B
General
Cylinder compression pressure (all engines) . . . . . . . . . . . . . . . . . . . . . 10 to 11 bars
Oil pressure (all engines)
At idle . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0.5 to 2.0 bars
Running (for example, at 4000 rpm) . . . . . . . . . . . . . . . . . . . . . . . . . . 4 bars or above (typically)
Cylinder head warpage limit
Except M40 engine . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0.10 mm
M40 engine . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0.03 mm
Minimum cylinder head thickness (do not resurface the head to a thickness less than listed)
M10 and M30 engines . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 128.6 mm
M20 engines . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 124.7 mm
M40 engine . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 140.55 mm
Valves
Valve stem diameter (standard)
M10 and M30 engines . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8.0 mm
M20 engine . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7.0 mm
M40 engine
Intake . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.975 mm
Exhaust . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.960 mm
Minimum valve margin width
Intake . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.191 mm
Exhaust . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.98 mm
Valve stem maximum lateral movement (see text) . . . . . . . . . . . . . . . . . 0.787 mm
Valve face angle
Intake . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45°
Exhaust . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45°
Chapter 2 Part B:
General engine overhaul procedures
Compression check . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
Crankshaft - inspection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
Crankshaft - refitting and main bearing oil clearance check . . . . . . . 24
Crankshaft - removal . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
Crankshaft rear oil seal - refitting . . . . . . . . . . . . . . . . . . . . . . . . . . . 25
Cylinder head and components - cleaning and inspection . . . . . . . 9
Cylinder head - dismantling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
Cylinder head - reassembly . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
Cylinder honing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
Engine - removal and refitting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
Engine block - cleaning . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
Engine block - inspection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
Engine overhaul - alternatives . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
Engine overhaul - dismantling sequence . . . . . . . . . . . . . . . . . . . . . 7Engine overhaul - general information . . . . . . . . . . . . . . . . . . . . . . . 2
Engine overhaul - reassembly sequence . . . . . . . . . . . . . . . . . . . . . 21
Engine removal - methods and precautions . . . . . . . . . . . . . . . . . . . 4
General information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
Initial start-up and break-in after overhaul . . . . . . . . . . . . . . . . . . . . 27
Intermediate shaft - refitting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
Intermediate shaft - removal and inspection . . . . . . . . . . . . . . . . . . . 14
Main and connecting big-end bearings - inspection . . . . . . . . . . . . 20
Piston rings - refitting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22
Pistons/connecting rods - inspection . . . . . . . . . . . . . . . . . . . . . . . . 18
Pistons/connecting rods - refitting and big-end bearing oil
clearance check . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26
Pistons/connecting rods - removal . . . . . . . . . . . . . . . . . . . . . . . . . . 12
Valves - servicing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
2B•1
Easy,suitable for
novice with little
experienceFairly easy,suitable
for beginner with
some experienceFairly difficult,
suitable for competent
DIY mechanic
Difficult,suitable for
experienced DIY
mechanicVery difficult,
suitable for expert
DIY or professional
Degrees of difficulty
Specifications Contents

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

4
Carburettor (Solex 2B4)
Main jet
Stage 1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . X120
Stage 2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . X90
Air correction jet
Stage 1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 135
Stage 2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 75
Venturi diameter
Stage 1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24 mm
Stage 2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28 mm
Idle/air jet
Stage 1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50/120
Stage 2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40/125
Float needle valve diameter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.0 mm
Choke gap (pulldown) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.0 to 5.5 mm
Throttle positioner spring preload . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22.0 to 24.0 mm
Float level
Stage 1 float chamber . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27.0 to 29.0 mm
Stage 2 float chamber . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29.0 to 31.0 mm
Chapter 4 Fuel and exhaust systems
Accelerator cable - check, adjustment and renewal . . . . . . . . . . . . . 9
Air cleaner assembly - removal and refitting . . . . . . . . . . . . . . . . . . . 8
Air filter renewal . . . . . . . . . . . . . . . . . . . . . . . . . . . . . See Chapter 1
Airflow meter - check, removal and refitting . . . . . . . . . . . . . . . . . . . 16
Carburettor - cleaning and adjustment . . . . . . . . . . . . . . . . . . . . . . . 12
Carburettor - general information . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
Carburettor - removal and refitting . . . . . . . . . . . . . . . . . . . . . . . . . . 11
Cold start injector and thermotime switch -
checkand renewal . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
Engine idle speed check and adjustment . . . . . . . . . See Chapter 1
Exhaust system check . . . . . . . . . . . . . . . . . . . . . . . . See Chapter 1
Exhaust system servicing - general information . . . . . . . . . . . . . . . . 22
Fuel filter renewal . . . . . . . . . . . . . . . . . . . . . . . . . . . See Chapter 1
Fuel injection system - check . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
Fuel injection system - depressurising . . . . . . . . . . . . . . . . . . . . . . . 2Fuel injection system - fault finding . . . . . . . . . . . . See end of Chapter
Fuel injection - general information . . . . . . . . . . . . . . . . . . . . . . . . . . 13
Fuel injection systems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
Fuel injectors - check and renewal . . . . . . . . . . . . . . . . . . . . . . . . . . 20
Fuel lines and fittings - repair and renewal . . . . . . . . . . . . . . . . . . . . 5
Fuel pressure regulator - check and renewal . . . . . . . . . . . . . . . . . . 18
Fuel pump, transfer pump and fuel level sender unit -
removal and refitting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
Fuel pump/fuel pressure - check . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
Fuel system check . . . . . . . . . . . . . . . . . . . . . . . . . . . See Chapter 1
Fuel tank - removal and refitting . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
Fuel tank cleaning and repair - general information . . . . . . . . . . . . . 7
General information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
Idle air stabiliser valve - check, adjustment and renewal . . . . . . . . . 21
Throttle body - check, removal and refitting . . . . . . . . . . . . . . . . . . . 17
4•1
Easy,suitable for
novice with little
experienceFairly easy,suitable
for beginner with
some experienceFairly difficult,
suitable for competent
DIY mechanic
Difficult,suitable for
experienced DIY
mechanicVery difficult,
suitable for expert
DIY or professional
Degrees of difficulty
Specifications Contents

Carburettor (Solex 2BE)
Main jet
Stage 1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . X120
Stage 2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . X110
Air correction jet
Stage 1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 140
Stage 2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 70
Venturi diameter
Stage 1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24 mm
Stage 2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28 mm
Idle fuel jet
Stage 1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47.5 mm
Idle air jet
Stage 2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 180
Float needle valve diameter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.0 mm
Throttle positioner coil resistance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0.97 to 1.63 ohms
Intake air temperature resistance
-10º C . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8200 to 10 500 ohms
20º C . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2200 to 2700 ohms
80º C . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 300 to 360 ohms
Float level
Stage 1 float chamber . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27.0 to 29.0 mm
Stage 2 float chamber . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29.0 to 31.0 mm
Fuel pressure checks (carburettor engines)
Fuel pump delivery pressure (engine idling) . . . . . . . . . . . . . . . . . . . . . . 0.1 to 0.3 bars
Fuel pressure checks (fuel injection engines)
Fuel system pressure (relative to intake manifold pressure)
3-Series (E30)
316i with M40/B16 engine . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.0 ± 0.06 bars
318i with M10/B18 engine . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.5 to 3.0 bars
318i with M40/B18 engine . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.0 ± 0.06 bars
320i with M20/B20 engine (L-Jetronic) . . . . . . . . . . . . . . . . . . . . . . 2.5 to 3.0 bars
320i with M20/B20 engine (Motronic) . . . . . . . . . . . . . . . . . . . . . . . 2.5 ± 0.05 bars
325i with M20/B25 engine . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.0 ± 0.05 bars
5-Series (E28/”old-shape”)
All models . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.5 to 3.0 bars
5-Series (E34/”new-shape”)
518i with M40/B18 engine . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.0 ± 0.06 bars
All other models . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.5 to 3.0 bars
Fuel system hold pressure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.1 bars
Fuel pump maximum pressure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.3 to 6.9 bars
Fuel pump hold pressure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.5 bars
Transfer pump pressure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0.28 to 0.35 bars
Injectors
Injector resistance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14.5 to 17.5 ohms
Accelerator cable free play . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.0 mm
Torque wrench settingsNm
Carburettor mountings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
Fuel pump to cylinder head . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
Throttle body nuts/bolts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19 to 26
4•2 Fuel and exhaust systems
1 General information
With the exception of early models (316 and
518 models) all engines are equipped with
electronic fuel injection.
Early 316 and 518 models are equipped
with Solex carburettors. The carburettor fitted
is either a Solex 2B4 (early models) or
2BE (later models). The mechanical fuel pumpis driven by an eccentric lobe on the
camshaft.
Fuel injection models are equipped with
either the L-Jetronic or the Motronic fuel
injection system. From 1988, fuel injection
models are equipped with an updated version
of the Motronic system - this system is easily
distinguished from the earlier system by the
absence of a cold start injector. The electric
fuel pump is located beneath the rear of the
vehicle, or inside the fuel tank. The fuel pump
relay on Motronic systems is activated from aearth signal from the Motronic control unit
(ECU). The fuel pump operates for a few
seconds when the ignition is first switched on,
and it continues to operate only when the
engine is actually running.Air intake system
The air intake system consists of the air
filter housing, the airflow meter and throttle
body (fuel injection models), and the intake
manifold. All components except the intake
manifold are covered in this Chapter; for