1987 BMW 5 SERIES brake light

material is bonded to a metal plate or shoe -
the metal portion is not included in this
measurement. Always renew the pads on
both sides of the vehicle (in axle sets), even if
only one pad of the four is worn, or uneven
braking may result.
12Remove the calipers without
disconnecting the brake hoses (see Chap-
ter 9).
13Check the condition of the brake disc.
Look for score marks, deep scratches and
overheated areas (they will appear blue or
discoloured). If damage or wear is noted, the
disc can be removed and resurfaced by an
engineering workshop; otherwise, it will have
to be renewed. In either case, both discs
should be involved, even if only one is worn.
Refer to Chapter 9 for more detailed
inspection and repair procedures.
Drum brakes
14Refer to Chapter 9 and remove the rear
brake drums.
15Note the thickness of the lining material
on the rear brake shoes, and look for signs of
contamination by brake fluid or grease (see
illustration). If the material is within 2.0 mm of
the recessed rivets or metal shoes, renew the
brake shoes. The shoes should also be
renewed if they are cracked, glazed (shiny
lining surfaces), or contaminated with brake
fluid or grease. See Chapter 9 for the renewal
procedure.
16Check the shoe return and hold-down
springs and the adjusting mechanism. Make
sure all these components are fitted correctly,and are in good condition. Deteriorated or
distorted springs, if not renewed, could allow
the linings to drag and wear prematurely.
17Check the wheel cylinders for leakage by
carefully peeling back the rubber boots. Slight
moisture behind the boots is acceptable. If
brake fluid is noted behind the boots or if it
runs out of the wheel cylinder, the wheel
cylinders must be overhauled or renewed (see
Chapter 9).
18Check the drums for cracks, score marks,
deep scratches and high spots, which will
appear as small discoloured areas. If
imperfections cannot be removed with emery
cloth, both drums must be resurfaced by a
specialist (see Chapter 9 for more detailed
information).
19Refer to Chapter 9 and fit the brake
drums.
20Refit the wheels, but don’t lower the
vehicle yet.
Handbrake
21The easiest, and perhaps most obvious,
method of checking the handbrake is to park
the vehicle on a steep hill with the handbrake
applied and the transmission in Neutral (stay
in the vehicle while performing this check). If
the handbrake doesn’t prevent the vehicle
from rolling, refer to Chapter 9 and adjust it.
27 Wiper blades -
check and renewal
1
1Road film can build up on the wiper blades
and affect their efficiency, so they should bewashed regularly with a mild detergent
solution.
Check
2The wiper and blade assembly should be
inspected periodically. If inspection reveals
hardened or cracked rubber, renew the wiper
blades. If inspection reveals nothing unusual,
wet the windscreen, turn the wipers on, allow
them to cycle several times, then switch them
off. An uneven wiper pattern across the glass,
or streaks over clean glass, indicate that the
blades should be renewed.
3The operation of the wiper mechanism can
loosen the retaining nuts, so they should be
checked and tightened, as necessary, at the
same time the wiper blades are checked (see
Chapter 12 for further information regarding
the wiper mechanism).
Wiper blade renewal
4Pull the wiper/blade assembly away from
the glass.
5Press the retaining tab in, and slide the
blade assembly down the wiper arm (see
illustration).
6If you wish to renew the blade rubbers
separately, detach the end of the rubber from
the wiper blade frame, then slide the rubber
out of the frame (see illustration).
7Compare the new rubber with the old for
length, design, etc.
8Slide the new rubber into place, and insert
the end in the wiper blade frame to lock it in
place.
9Refit the blade assembly on the arm, then
wet the glass and check for proper operation.
1•23
27.6 Detach the end of the wiper element
from the end of the frame, then slide the
element out27.5 Press the retaining tab in, then slide
the wiper blade assembly down and out of
the hook in the end of the wiper arm26.15 If the lining is bonded to the brake
shoe, measure the lining thickness from
the outer surface to the metal shoe, as
shown here (A); if the lining is riveted to
the shoe, measure from the lining outer
surface to the rivet head
1
Every 12 000 miles
Every 24 000 miles or 2 years, whichever comes first
28 Automatic transmission fluid
and filter change
1
1At the specified intervals, the transmission
fluid should be drained and renewed. Since
the fluid will remain hot long after driving,perform this procedure only after the engine
has cooled down completely.
2Before beginning work, purchase the
specified transmission fluid (see “Lubricants
and fluids”at the beginning of this Chapter)
and a new filter.
3Other tools necessary for this job include axle
stands or ramps to support the vehicle in araised position, a drain pan capable of holding at
least 4.5 litres, and newspapers and clean rags.
4Raise the vehicle and support it securely.
5Loosen the dipstick tube collar, then detach
the dipstick tube and let the fluid drain (see
illustrations).
6Remove the transmission sump mounting
bolts and brackets (see illustration).

the lubricant will be hot, it would be wise to
wear rubber gloves.
3Raise the vehicle and place it on axle
stands. Make sure it is safely supported, and
as level as possible.
4Move the necessary equipment under the
vehicle, being careful not to touch any of the
hot exhaust components.
5Place the drain pan under the transmission,
and remove the filler/level plug from the side
of the transmission. Loosen the drain plug
(see illustration).
6Carefully remove the drain plug. Be careful
not to burn yourself on the lubricant.
7Allow the lubricant to drain completely.
Clean the drain plug thoroughly, then refit and
tighten it securely.
8Refer to Section 16 and fill the transmission
with new lubricant, then refit the filler/level
plug, tightening it securely.
9Lower the vehicle. Check for leaks at the
drain plug after the first few miles of driving.
32 Differential lubricant change
1
1Drive the vehicle for several miles to warm
up the differential lubricant, then raise the
vehicle and support it securely on axle stands.
2Move a drain pan, rags, newspapers and an
Allen key under the vehicle. Since the
lubricant will be hot, wear rubber gloves to
prevent burns.
3Remove the filler/level plug from the
differential; this is the upper of the two plugs.
4With the drain pan under the differential,
loosen the drain plug; this is the lower of the
two plugs (see illustration).
5Carefully unscrew the drain plug until you
can remove it from the case.
6Allow all the oil to drain into the pan, then
refit the drain plug and tighten it securely.
7Refer to Section 17 and fill the differential
with lubricant.
8Refit the filler/level plug and tighten it
securely.
9Lower the vehicle. Check for leaks at the
drain plug after the first few miles of driving.
33 Evaporative emissions
control (EVAP) system check
1
1The function of the evaporative emissions
control system is to draw fuel vapours from
the tank and fuel system, store them in a
charcoal canister, and then burn them during
normal engine operation. This system is
normally only fitted to those vehicles
equipped with a catalytic converter.
2The most common symptom of a fault in
the evaporative emissions system is a strong
fuel odour in the engine compartment. If a fuel
odour is detected, inspect the charcoal
canister and system hoses for cracks. The
canister is located in the front corner of the
engine compartment on most models (see
illustration).
3Refer to Chapter 6 for more information on
the evaporative emissions system.
34 Service indicator light
resetting
4
Service indicator lights
1All models covered in this manual are
equipped with various service indicator lights
on the facia, which automatically go on when
the mileage interval is reached. These lights
can only be turned off by using a special tool
which plugs into the service connector
located in the engine compartment.
2Although the service light resetting tool can
be obtained from a dealer, reasonably-priced
alternatives may also be available from
aftermarket sources. When obtaining a tool, it
is important to know the vehicle year and
model, and whether the service connector has
15 or 20 pins (see illustrations). Once the
proper tool is obtained, it is a simple matter to
plug it into the service connector and,
following the tool manufacturer’s instructions,
reset the service lights. Note: The brake
warning light will not automatically reset if the
sensor on the brake pad (or its wiring) isdamaged because it is worn through: it must
be repaired first.
3The service lights are controlled by the
Service Indicator (SI) board in the instrument
cluster, which is powered by rechargeable
batteries. Should these batteries fail,
problems will develop in the SI board.
Symptoms of failed batteries include the
inability to reset the service lights and
malfunctions affecting the tachometer,
temperature gauge and radio operation. Refer
to Chapter 12 for more information on the SI
board.
Every 60 000 miles
35 Engine timing belt renewal
5
Note:This is not included in the
manufacturer’s maintenance schedule, but is
strongly recommended as a precaution
against the timing belt failing in service. If the
timing belt fails while the engine is running,
extensive engine damage could be caused.
Refer to Chapter 2A, Section 10.
1•26
34.2b An aftermarket service light
resetting tool such as this one can be
plugged into the service connector and
used to reset the service lights
34.2a The earlier 15-pin connector
(arrowed) is mounted near the front of the
engine. The 20-pin connector used on later
models is located in the left rear corner of
the engine compartment33.2 Inspect the hoses (arrowed) at the
top of the evaporative emissions charcoal
canister for damage32.4 Remove the differential drain plug
with an Allen key
Every 24 000 miles

7 Ignition timing (TCI system)-
check and adjustment
4
Warning: Keep hands, equipment
and wires well clear of the
viscous cooling fan during
adjustment of the ignition timing.
Note:This Section describes the procedure
for checking and adjusting the ignition timing
on engines fitted with the TCI system. On
engines fitted with the Motronic engine
management system, the ignition timing is
controlled by the electronic control unit, and
no adjustment is possible. The timing can be
checked using the following procedure, but no
ignition timing values were available at the
time of writing. If the timing is thought to be
incorrect, refer to a BMW dealer.
1Some special tools are required for this
procedure (see illustration). The engine must
be at normal operating temperature, and the
air conditioning (where fitted) must be
switched off. Make sure the idle speed is
correct.
2Apply the handbrake, and chock the wheels
to prevent movement of the vehicle. The
transmission must be in neutral (manual) or
Park (automatic).
3The timing marks are located on the engine
flywheel (viewed through the timing checkhole in the bellhousing) and/or on the vibration
damper on the front of the engine.
4Where applicable, disconnect the vacuum
hose from the distributor vacuum advance
unit.
5Connect a tachometer and timing light
according to the equipment manufacturer’s
instructions (an inductive pick-up timing light
is preferred). Generally, the power leads for
the timing light are attached to the battery
terminals, and the pick-up lead is attached to
the No 1 spark plug HT lead. The No 1 spark
plug is the one at the front of the engine.
Caution: If an inductive pick-up
timing light isn’t available, don’t
puncture the spark plug HT lead
to attach the timing light pick-up
lead. Instead, use an adapter between the
spark plug and HT lead. If the insulation on
the HT lead is damaged, the secondary
voltage will jump to earth at the damaged
point, and the engine will misfire.
Note:On some models, a TDC transmitter is
fitted for checking the ignition system.
However, a special BMW tester must be
connected to the diagnostic socket to use it,
so unless the special tester is available, a
conventional timing light should be used. The
ignition timing mark may be on the vibration
damper, but if not, normally the TDC mark will
be. If the timing light is of the adjustable delay
type, then the ignition timing may be
determined by zeroing the adjustment, then
turning the adjustment until the TDC marks are
aligned, and then reading off the amount of
advance from the timing light. If a standard
timing light is being used, make a mark on the
vibration damper in accordance with the
specified advance, using the following formula
to calculate the distance from the TDC mark
to the timing mark:
Distance = 2Pr x advance
360
where P = 3.142
r = radius of vibration damper
advance = specified advance
BTDC in degrees
6With the ignition off, loosen the distributor
clamp nut just enough to allow the distributor
to pivot without any slipping.7Make sure the timing light wires are routed
away from the drivebelts and fan, then start
the engine.
8Raise the engine rpm to the specified
speed, and then point the flashing timing light
at the timing marks - be very careful of moving
engine components.
9The mark on the flywheel or vibration
damper will appear stationary. If it’s aligned
with the specified point on the bellhousing or
engine front cover, the ignition timing is
correct (see illustrations).
10If the marks aren’t aligned, adjustment is
required. Turn the distributor very slowly until
the marks are aligned, taking care not to
touch the HT leads.
11Tighten the nut on the distributor clamp,
and recheck the timing.
12Switch off the engine, and remove the
timing light and tachometer. Reconnect the
vacuum hose where applicable.
8 Distributor-
removal and refitting
4
TCI system
Removal
1After carefully marking them for position,
remove the coil HT lead and spark plug HT
leads from the distributor cap (see Chapter 1).
2Remove No 1 spark plug (the one nearest
you when you are standing in front of the
engine).
3Manually rotate the engine to Top Dead
Centre (TDC) on the compression stroke for
No 1 piston (see Chapter 2A)
4Carefully mark the vacuum hoses, if more
than one is present on your distributor.
5Disconnect the vacuum hose(s).
6Disconnect the primary circuit wires from
the distributor.
7Mark the relationship of the rotor tip to the
distributor housing (see illustration). Also
mark the relationship of the distributor
housing to the engine.
5•4 Engine electrical systems
7.1 Tools for checking and adjusting the
ignition timing
1Vacuum plugs- Vacuum hoses will, in
most cases, have to be disconnected and
plugged. Moulded plugs in various shapes
and sizes can be used for this, if wished
2Inductive pick-up timing light- Flashes a
bright, concentrated beam of light when
No 1 spark plug fires. Connect the leads
according to the instructions supplied with
the light
3Distributor spanner - On some models,
the hold-down bolt for the distributor is
difficult to reach and turn with conventional
spanners or sockets. A special spanner like
this must be used
7.9a Flywheel “OT” timing mark 7.9b Flywheel “OZ” timing mark

9
General
Brake fluid type . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . See Chapter 1
Disc brakes
Minimum brake pad thickness . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . See Chapter 1
Brake disc minimum permissible thickness (wear limit)*
Front
3-Series
Solid discs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10.7 mm
Ventilated discs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20.0 mm
5-Series
Solid discs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10.0 mm
Ventilated discs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20.0 mm
Rear . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8.0 mm
Brake disc minimum thickness after machining
Front
3-Series
Solid discs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11.1 mm
Ventilated discs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20.4 mm
5-Series
Solid discs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10.4 mm
Ventilated discs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20.4 mm
Rear . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8.4 mm
Parallelism (difference between any two measurements) . . . . . . . . . . . 0.02 mm
Maximum disc run-out . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0.2 mm
*Refer to marks cast into the disc (they supersede information printed here)
Brake pedal adjustments
Brake pedal/servo pushrod adjustment (A) (3-Series) . . . . . . . . . . . . . . 125 mm
Brake pedal height (pedal-to-bulkhead distance)
3-Series
Left-hand-drive . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 235 mm
Right-hand-drive . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 273 mm
5-Series . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 245 mm
Stop-light switch adjustment (dimension A - see text) . . . . . . . . . . . . . . 5.0 mm to 6.0 mm
Handbrake
Handbrake shoe lining minimum thickness . . . . . . . . . . . . . . . . . . . . . . 1.5 mm
Handbrake lever travel . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 to 8 clicks
Chapter 9 Braking system
Anti-lock brake system (ABS) - general information . . . . . . . . . . . . . 2
Brake check . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . See Chapter 1
Brake disc - inspection, removal and refitting . . . . . . . . . . . . . . . . . 5
Brake fluid level check . . . . . . . . . . . . . . . . . . . . . . . . See Chapter 1
Brake hoses and lines - inspection and renewal . . . . . . . . . . . . . . . . 15
Brake hydraulic system - bleeding . . . . . . . . . . . . . . . . . . . . . . . . . . 16
Brake pedal - adjustment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
Brake vacuum servo - check, removal and refitting . . . . . . . . . . . . . 8
Disc brake caliper - removal, overhaul and refitting . . . . . . . . . . . . . 4Disc brake pads - renewal . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
Drum brake shoes - renewal . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
General information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
Handbrake assembly - check, removal and refitting . . . . . . . . . . . . 12
Handbrake - adjustment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
Handbrake cable(s) - renewal . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
Hydraulic brake servo - description, removal and refitting . . . . . . . . 9
Master cylinder - removal and refitting . . . . . . . . . . . . . . . . . . . . . . . 7
Stop-light switch - check and adjustment . . . . . . . . . . . . . . . . . . . . 14
9•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

Torque wrench settingsNm
Front disc brake caliper
Caliper guide (mounting) bolts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30 to 35
Caliper bracket-to-strut housing bolts
3-Series, E30 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 123
5-Series, E28 (“old-shape”) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 123
5-Series, E34 (“new-shape”) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 110
Rear disc brake caliper
Caliper guide (mounting) bolts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30 to 35
Carrier-to-trailing arm bolts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 67
Brake hose-to-caliper fitting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14 to 17
Master cylinder-to-brake servo nuts
3-Series . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24
5-Series . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25 to 29
Brake servo mounting nuts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22 to 24
Hydraulic line-to-hydraulic brake servo threaded
fittings - 5-Series, E28 (“old-shape”) . . . . . . . . . . . . . . . . . . . . . . . . . . . 31
Wheel bolts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . See Chapter 1
9•2 Braking system
1 General information
All 3-Series models, and 5-Series E28 (“old-
shape”) models, are equipped with front disc
brakes and either rear drum or rear disc
brakes. 5-Series E34 (“new-shape”) models
have disc brakes front and rear. Front and
rear brakes are self-adjusting on all models.
Some later models are equipped with an Anti-
lock Braking System (ABS); this is described
in Section 2.
Hydraulic system
The hydraulic system consists of two
separate circuits. The master cylinder has
separate reservoirs for the two circuits; in the
event of a leak or failure in one hydraulic
circuit, the other circuit will remain operative.
Brake servo
The vacuum brake servo, utilising engine
manifold vacuum and atmospheric pressure
to provide assistance to the hydraulically
operated brakes, is mounted on the bulkhead
in the engine compartment.
A hydraulic brake servo system is used on
5-Series E28 models. This system uses
hydraulic pressure from the power steering
pump to assist braking.
Handbrake
The handbrake operates the rear brakes,
and is cable-operated via a lever mounted in
the centre console. The handbrake assembly
on rear drum brake models is part of the rear
drum brake assembly, and is self-adjusting.
On rear disc brake models, the handbrake
uses a pair of brake shoes located inside the
centre portion of the rear brake disc, and is
manually-adjusted.
Brake pad wear warning system
The brake pad wear warning system is
linked to a red warning light in the instrumentcluster, which comes on when the brake pads
have worn down to the point at which they
require renewal. DO NOT ignore this reminder.
If you don’t renew the pads shortly after the
brake pad wear warning light comes on, the
brake discs will be damaged.
On some models, the brake pad wear
warning system also includes an early
warning light that comes on only when the
brake pedal is depressed, letting you know in
advance that the pads need to be renewed.
The wear sensor is attached to the brake
pads. The sensor is located at the left front
wheel; on some models, there is another
sensor at the right rear wheel. The wear
sensor is part of a closed circuit. Once the
pads wear down to the point at which they’re
flush with the sensor, the disc grinds away the
side of the sensor facing the disc. Thus, the
wire inside the sensor is broken, and the red
light on the instrument panel comes on.
Always check the sensor(s) when renewing
the pads. If you change the pads before the
warning light comes on, the sensor(s) may still
be good; once the light has come on, renew
the sensor.
Service
After completing any operation involving
dismantling of any part of the brake system,
always test drive the vehicle to check for
proper braking performance before resuming
normal driving. When testing the brakes, try to
select a clean, dry, road with no camber (ie as
flat as possible) and with no other traffic.
Conditions other than these can lead to
inaccurate test results.
Test the brakes at various speeds with both
light and heavy pedal pressure. The vehicle
should stop evenly, without pulling to one side
or the other. Avoid locking the brakes,
because this slides the tyres and diminishes
braking efficiency and control of the vehicle.
Tyres, vehicle load and wheel alignment are
factors which also affect braking
performance.
2 Anti-lock Braking system
(ABS)- general information
The Anti-lock Braking System is designed
to maintain vehicle control, directional stability
and optimum deceleration under severe
braking conditions on most road surfaces. It
does so by monitoring the rotational speed of
each wheel and controlling the brake line
pressure to each wheel during braking. This
prevents the wheels from locking up.
The ABS system has three main
components - the wheel speed sensors, the
electronic control unit, and the hydraulic
control unit. The sensors - one at each wheel
since 1985, but at both front wheels and one
at the rear differential on earlier models - send
a variable voltage signal to the control unit,
which monitors these signals, compares them
to its program information, and determines
whether a wheel is about to lock up. When a
wheel is about to lock up, the control unit
signals the hydraulic unit to reduce hydraulic
pressure (or not increase it further) at that
wheel’s brake caliper. Pressure modulation is
handled by electrically-operated solenoid
valves.
If a problem develops within the system, an
“ABS” warning light will glow on the
dashboard. Sometimes, a visual inspection of
the ABS system can help you locate the
problem. Carefully inspect the ABS wiring
harness. Pay particularly close attention to the
harness and connections near each wheel.
Look for signs of chafing and other damage
caused by incorrectly-routed wires. If a wheel
sensor harness is damaged, the sensor
should be renewed (the harness and sensor
are integral).
Warning: DO NOT try to repair an
ABS wiring harness. The ABS
system is sensitive to even the
smallest changes in resistance. Repairing
the harness could alter resistance values

and cause the system to malfunction. If
the ABS wiring harness is damaged in any
way, it must be renewed.
Caution: Make sure the ignition is
turned off before unplugging or
re-making any electrical
connections.
Diagnosis and repair
If the dashboard warning light comes on
and stays on while the vehicle is in operation,
the ABS system requires attention. Although
special electronic ABS diagnostic testing
tools are necessary to properly diagnose the
system, you can perform a few preliminary
checks before taking the vehicle to a dealer
service department.
a) Check the brake fluid level in the
reservoir.
b) Verify that the electronic control unit
connectors are securely connected.
c) Check the electrical connectors at the
hydraulic control unit.
d) Check the fuses.
e) Follow the wiring harness to each front
and rear wheel, and verify that all
connections are secure and that the
wiring is undamaged.
If the above preliminary checks do not
rectify the problem, the vehicle should bediagnosed by a dealer service department.
Due to the complex nature of this system, all
actual repair work must be done by a dealer
service department.
3 Disc brake pads- renewal
2
Warning: Disc brake pads must
be renewed on both front wheels
or both rear wheels at the same
time - NEVER renew the pads on
only one wheel. Also, the dust created by
the brake system may contain asbestos,
which is harmful to your health. Never
blow it out with compressed air, and don’t
inhale any of it. An approved filtering mask
should be worn when working on the
brakes. Do not, under any circumstances,
use petroleum-based solvents to clean
brake parts. Use brake system cleaner
only! When servicing the disc brakes, use
only original-equipment or high-quality
brand-name pads.
Warning: Brake fluid is
poisonous. It is also an effective
paint stripper. Refer to the
warning at the start of Section 16.
Note:This procedure applies to both the front
and rear disc brakes.
1Remove the cap(s) from the brake fluid
reservoir, and syphon off about two-thirds of
the fluid from the reservoir. Failing to do thiscould result in the reservoir overflowing when
the caliper pistons are pressed back into their
bores.
2Loosen the wheel bolts, raise the front or
rear of the vehicle and support it securely on
axle stands.
3Remove the front or rear wheels, as
applicable. Work on one brake assembly at a
time, using the assembled brake for reference
if necessary.
4Inspect the brake disc carefully as outlined
in Section 5. If machining is necessary, follow
the information in that Section to remove the
disc, at which time the pads can be removed
from the calipers as well.
5Follow the accompanying photos,
beginning with illustration 3.5a, for the pad
removal procedure. Be sure to stay in order,
and read the caption under each illustration.
Note 1:Different types of front calipers are
used on 3 and 5-Series models. Illustrations
3.5a to 3.5e are for the front calipers on 3-
Series models.Illustrations 3.5f to 3.5m are
for the front calipers on 5-Series models.
There’s no photo sequence for rear calipers;
although slightly different in size, they’re
identical in design to the front brake calipers
used on 5-Series models.Note 2: Some
models may have different numbers and types
of anti-squeal shims and other hardware than
what is shown in this Chapter. It’s best to note
how the hardware is fitted on the vehicle
before dismantling, so you can duplicate it on
reassembly.
Braking system 9•3
3.5c Hold the guide pins while loosening
the caliper mounting bolts (3-Series)3.5b Unplug the electrical connector for
the brake pad wear sensor (3-Series)
3.5a On 3-Series models, unscrew the
caliper mounting bolts (left arrows); right
arrows point to the caliper bracket bolts,
which should only be removed if you’re
removing the brake disc
3.5f On 5-Series models, unplug the
electrical connector for the brake pad
wear sensor3.5e Remove the outer brake pad
(3-Series) - to fit the new pads, reverse the
removal procedure
3.5d Remove the caliper, brake pad wear
sensor and inner pad all at the same time
(3-Series), then refit the inner pad on the
piston and press the piston fully into the
bore with a C-clamp
9

illustration). Use only low pressure, such as
that produced by a foot pump, to ease the
piston out of its bore.
Warning: Be careful not to place
your fingers between the piston
and the caliper, as the piston
may come out with some force. If
you’re working on a front caliper of a 3-
Series model, remove the dust boot.
6Inspect the mating surfaces of the piston
and caliper bore wall. If there is any scoring,
rust, pitting or bright areas, renew the
complete caliper unit.
7If these components are in good condition,
remove the piston seal from the caliper bore
using a wooden or plastic tool (see
illustration). Metal tools may damage the
cylinder bore.
8Remove the caliper guide pins or bolts and
remove the rubber dust boots.
9Wash all the components using methylated
spirit or brake system cleaner.
10Using the correct overhaul kit for your
vehicle, reassemble the caliper as follows.
11Dip the new rubber seal in clean brake
fluid, and refit it in the lower groove in the
caliper bore, making sure it isn’t twisted.
12On all calipers except the front calipers of
3-Series models, coat the walls of the caliperbore and the piston with clean brake fluid, and
refit the piston at this time. Do not force the
piston into the bore, but make sure that it is
squarely in place, then apply firm (but not
excessive) pressure to refit it. Fit the new
rubber dust boot and the retaining ring.
13On the front calipers of 3-Series models,
coat the piston with clean brake fluid, and
stretch the new dust boot over the bottom of
the piston. Hold the piston over the caliper
bore, and insert the rubber flange of the dust
boot into the upper groove in the bore. Start
with the furthest side from you, and work your
way around towards the front until it is
completely seated. Push the piston into the
caliper bore until it is bottomed in the bore,
then seat the top of the dust boot in the
groove in the piston.
14Lubricate the sliding surfaces of the guide
pins or bolts with silicone-based grease
(usually supplied in the kit), and push them
into the caliper. Refit the dust boots.
Refitting
15Refit the caliper by reversing the removal
procedure (see Section 3).
Warning: Check and if necessary
renew the mounting bolts on 3-
Series models whenever they are
removed. If in doubt, use new bolts.16If the hose was disconnected from the
caliper, bleed the brake system (see Sec-
tion 16).
5 Brake disc- inspection,
removal and refitting
2
Note:This procedure applies to both the front
and rear brake discs. Brake discs should
always be renewed or refinished in pairs (both
front or both rear discs) even if only one is
damaged or defective.
Braking system 9•5
4.4b Remove the circlip for the dust seal
4.4a An exploded view of a typical rear caliper assembly (front calipers similar)
4.7 Remove the piston seal from the
caliper bore using a wooden or plastic tool
(metal tools may damage the
cylinder bore)
1 Caliper assembly
2 Bracket mounting bolt
3 Bleed screw
4 Dust cap
5 Anti-rattle spring
6 Guide bolt
7 Brake pad wear warning
light wire8 Cable clamp
9 Brake disc
10 Allen bolt
11 Shield
12 Bolt
13 Washer
14 Plug15 Plug
16 Caliper bracket
17 Cable clamp
18 Piston seal, piston, dust
boot and circlip
19 Guide bush repair kit
20 Brake pads4.5 With the caliper padded to catch the
piston, use low pressure compressed air
to force the piston out of its bore - make
sure your fingers are not between the
piston and the caliper
9

Inspection
1Loosen the wheel bolts, raise the vehicle
and support it securely on axle stands.
Remove the wheel, and refit three bolts to
hold the disc in place. If the rear brake disc is
being worked on, release the handbrake.
2Remove the brake caliper as outlined in
Section 4. It is not necessary to disconnect
the brake hose. After removing the caliper,
suspend it out of the way with a piece of wire.
Remove the caliper mounting bracket (see
illustration).
3Inspect the disc surface for scoring, cracks
or other damage. Light scratches and shallow
grooves are normal after use, and are not
usually detrimental to brake operation, but
deep scoring requires disc removal andrenewal, or (if possible) refinishing by a
specialist. If a disc is cracked it must be
renewed. Be sure to check both sides of the
disc (see illustration). If severe vibration has
been noticed during application of the brakes,
the discs may be warped (excessive run-out).
If the vehicle is equipped with the Anti-lock
Braking System (ABS), do not confuse
vibration caused by warped discs with normal
operation of the ABS. It is quite normal for
some vibration to be felt through the pedal
when the system is working.
4To check disc run-out, place a dial indicator
at a point about 13 mm from the outer edge of
the disc (see illustration). Set the indicator to
zero, and rotate the disc. The indicator
reading should not exceed the specifiedallowable run-out limit. If it does (and if the
run-out is not due to wheel bearing wear), the
disc should be renewed or (if possible)
refinished by a specialist. Note:It is
recommended that the discs be resurfaced
regardless of the dial indicator reading, as this
will impart a smooth finish and ensure a
perfectly flat surface, eliminating any vibration
felt through the brake pedal or other
undesirable symptoms related to questionable
discs. At the very least, if you elect not to have
the discs resurfaced, remove the glazing from
the surface with emery cloth or sandpaper,
using a swirling motion (see illustration).
5It is absolutely critical that the disc not be
machined to a thickness less than that
specified. The minimum wear (or discard)
thickness is stamped into the hub of the disc.
The disc thickness can be checked with a
micrometer (see illustration).
Removal
6Remove the disc retaining screw (see
illustration) and remove the disc from the hub
(see illustration). If the disc is stuck to the
hub, spray a generous amount of penetrating
oil onto the area between the hub and the disc
(see illustration)and allow a few minutes for
it to loosen the rust between the two
components. If a rear disc still sticks, insert a
thin, flat-bladed screwdriver through the hub
flange, rotate the starwheel on the handbrake
9•6 Braking system
5.6c If the disc is stuck to the hub, spray
some penetrating oil onto the area
between the hub and the disc, and give the
oil a few minutes to separate the two parts
5.6b . . . and remove the disc from
the hub5.6a Remove the disc retaining screw . . .
5.5 The disc thickness can be checked
with a micrometer5.4b Using a swirling motion, remove the
glaze from the disc surface with
sandpaper or emery cloth
5.4a To check disc run-out, mount a dial
indicator as shown, and rotate the disc5.3 The brake pads on this vehicle were
obviously neglected, as the backing plate
cut deep grooves into the disc - wear this
severe means the disc must be renewed5.2 Remove the caliper mounting bracket
bolts (arrowed) and remove the bracket