Air con BMW 3 SERIES 1988 E30 Workshop Manual

On some models, it will be necessary to
release the retaining clip (see illustration).
13Visually examine the canister for leakage
or damage.
14Renew the canister if you find evidence of
damage or leakage.
7 Catalytic converter
1
General description
1To reduce emissions of unburnt
hydrocarbons (HC), carbon monoxide (CO)
and oxides of nitrogen (NOx), the later
vehicles covered by this manual are equipped
with a catalytic converter (see illustration).
The converter contains a ceramic honeycomb
coated with precious metals, which speed up
the reaction between the pollutants listed
previously and the oxygen in the exhaust gas.
The pollutants are oxidised to produce water
(H
2O), nitrogen and carbon dioxide (CO2).
Check
2Visually examine the converter(s) for cracks
or damage. Make sure all nuts and bolts are
tight.
3Inspect the insulation cover (if applicable)
welded onto the converter - it should not be
loose.
Caution: If an insulation cover is
dented so that it touches the
converter housing inside,
excessive heat may be
transferred to the floor.
4Start the engine and run it at idle speed.
5Check for exhaust gas leakage from the
converter flanges. Check the body of each
converter for holes.
Component renewal
6See Chapter 4 for removal and refitting
procedures.
Precautions
7The catalytic converter is a reliable and
simple device, which needs no maintenance
in itself, but there are some facts of which an
owner should be aware, if the converter is to
function properly for its full service life.
(a) DO NOT use leaded (eg UK “4-star”)
petrol in a car equipped with a catalytic
converter - the lead will coat the precious
metals, reducing their converting
efficiency, and will eventually destroy the
converter.
(b) Always keep the ignition and fuel systems
well-maintained in accordance with the
manufacturer’s schedule, as given in
Chapter 1. In particular, ensure that the air
cleaner filter element, the fuel filter (where
fitted) and the spark plugs are renewed at
the correct interval. If the intake air/fuel
mixture is allowed to become too rich due
to neglect, unburned fuel will enter the
catalytic converter, overheating the
element and eventually destroying the
converter.
(c) If the engine develops a misfire, do not
drive the car at all (or at least as little as
possible) until the fault is cured - the
misfire will allow unburned fuel to enter
the converter, which will result in its
overheating, as noted above.
(d) DO NOT push- or tow-start the car - this
will soak the catalytic converter in
unburned fuel, causing it to overheat
when the engine does start - see (b) or (c)
above.
(e) DO NOT switch off the ignition at high
engine speeds - ie do not “blip” the
throttle immediately before switching offthe engine. If the ignition is switched off
at anything above idle speed, unburned
fuel will enter the (very hot) catalytic
converter, with the possible risk of its
igniting on the element and damaging the
converter.
(f) DO NOT use fuel or engine oil additives -
these may contain substances harmful to
the catalytic converter.
(g) DO NOT continue to use the car if the
engine burns oil to the extent of leaving a
visible trail of blue smoke - the unburned
carbon deposits will clog the converter
passages, and reduce its efficiency; in
severe cases, the element will overheat.
(h) Remember that the catalytic converter
operates at very high temperatures -
hence the heat shields on the car’s
underbody - and the casing will become
hot enough to ignite combustible
materials which brush against it. DO NOT,
therefore, park the car in dry
undergrowth, or over long grass or piles
of dead leaves.
(i) Remember that the catalytic converter is
FRAGILE - do not strike it with tools
during servicing work, and take great care
when working on the exhaust system.
Ensure that the converter is well clear of
any jacks or other lifting gear used to raise
the car, and do not drive the car over
rough ground, road humps, etc, in such a
way as to “ground” the exhaust system.
(j) In some cases, particularly when the car
is new and/or is used for stop/start
driving, a sulphurous smell (like that of
rotten eggs) may be noticed from the
exhaust. This is common to many
catalytic converter-equipped cars, and
seems to be due to the small amount of
sulphur found in some petrols reacting
with hydrogen in the exhaust, to produce
hydrogen sulphide (H
2S) gas; while this
gas is toxic, it is not produced in sufficient
amounts to be a problem. Once the car
has covered a few thousand miles, the
problem should disappear - in the
meanwhile, a change of driving style, or of
the brand of petrol used, may effect a
solution.
(k) The catalytic converter, used on a well-
maintained and well-driven car, should
last for 50 000 to 100 000 miles - from
this point on, the CO level should be
carefully checked regularly, to ensure that
the converter is still operating efficiently. If
the converter is no longer effective, it
must be renewed.
6•6 Engine management and emission control systems
7.1 Typical catalytic converter (M10
engine type shown, others similar)6.12 EVAP system charcoal canister
viewed from under the vehicle (316i model)

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

6Be sure to inspect the wear sensor(s) (left
front wheel only, or left front and right rear
wheel). If they’re OK, transfer them from the
old pads to the new ones; if they’re worn by
abrasion, fit new sensors on the new pads.
7To fit the new pads, reverse the removal
procedure. When refitting the caliper, be sure
to tighten the mounting bolts to the torque
listed in this Chapter’s Specifications.
Warning: Check and if necessary
renew the mounting bolts on 3-
Series models whenever they are
removed. If in doubt, use new
bolts.
8After the job is completed, firmly depress
the brake pedal a few times, to bring the pads
into contact with the discs. The pedal shouldbe at normal height above the floor, and firm.
Check the level of the brake fluid, adding
some if necessary. Check carefully for leaks,
and check the operation of the brakes before
returning the vehicle to normal service.
9Avoid heavy braking as far as possible for
the first hundred miles or so until the new
pads have bedded in.
4 Disc brake caliper- removal,
overhaul and refitting
4
Warning: 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!
Warning: Brake fluid is
poisonous. It is also an effective
paint stripper. Refer to the
warning at the start of Section 16.
Note:If an overhaul is indicated (usually
because of fluid leakage), explore all options
before beginning the job. Overhauled calipers
may be available on an exchange basis, which
makes this job quite easy. If you decide to
overhaul the calipers, make sure that anoverhaul kit is available before proceeding.
Always overhaul the calipers in pairs - never
overhaul just one of them.
Removal
1Loosen the wheel bolts, raise the front or
rear of the vehicle, and place it securely on
axle stands. Remove the wheel.
2If you’re just removing the caliper for
access to other components, it isn’t
necessary to detach the brake line. If you’re
removing the caliper for overhaul, disconnect
the brake line from the caliper, for preference
using a split ring (“brake”) spanner to protect
the fitting. Plug the line, to keep contaminants
out of the brake system and to prevent losing
brake fluid unnecessarily.
3Refer to Section 3 for the front or rear
caliper removal procedure - it’s part of the
brake pad renewal procedure. Note:The rear
caliper is similar in design to the front caliper
on 5-series models.
Overhaul
4On all calipers except the front calipers on
3-Series models, remove the circlip for the
dust seal (see illustration),then remove the
dust boot (see illustration). Before you
remove the piston, place a block of wood
between the piston and caliper to prevent
damage as it is removed.
5To remove the piston from the caliper,
apply compressed air to the brake fluid hose
connection on the caliper body (see
9•4 Braking system
3.5l Hang the caliper out of the way with a
piece of wire
3.5m Remove the outer brake pad - to fit
the new pads, reverse the removal
procedure
3.5k Unclip the inner brake pad from the
piston (5-Series)3.5j Remove the caliper and inner brake
pad (5-Series)
3.5i Depress the piston with a C-clamp
(5-Series)3.5h Prise off the anti-rattle spring
(5-Series)3.5g Remove the plugs for the brake
caliper mounting bolts, then remove the
bolts (5-Series)

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

adjusting screw and contract the handbrake
shoes (see illustration).
Refitting
7Ensure that the disc is completely clean
before refitting. If penetrating oil was used to
remove the disc, make sure that no trace of
this is present. Place the disc on the hub, and
refit the disc retaining screw. Tighten the
screw securely.
8Refit the caliper mounting bracket (if
removed), brake pads and caliper (see
Sections 3 and 4). Tighten all fasteners to the
torques listed in this Chapter’s Specifications.
9Refit the wheel, then lower the vehicle to
the ground. Depress the brake pedal a few
times to bring the brake pads into contact
with the disc.
10Adjust the handbrake shoes, if necessary
(Section 11).
11Check the operation of the brakes
carefully before returning the vehicle to
normal service.
6 Drum brake shoes- renewal
2
Warning: Brake shoes must be
renewed on both wheels at the
same time - never renew the
shoes 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. Always wear
an approved filtering mask when servicing
the brake system. Do not, under anycircumstances, use petroleum-based
solvents to clean brake parts. Use brake
system cleaner only.
Caution: Whenever the brake
shoes are renewed, new return
and hold-down springs and new
automatic adjuster thermo-clips
should also be fitted. Due to the
continuous heating/cooling cycle to which
the springs are subjected, they may lose
their tension over a period of time,
allowing the shoes to drag on the drum,
and wear at a much faster rate than
normal. When fitting new brake shoes, use
only original-equipment or high-quality
brand name parts.
Note 1:All four rear brake shoes must be
renewed at the same time, but to avoid mixing
up parts, work on only one brake assembly at
a time. Some rear brake components are
different for left and right-hand sides, so don’t
mix them up.
Note 2:If the wheel cylinder is found to be
leaking or otherwise defective, renew it after
removing the brake shoes. This is simply a
matter of disconnecting the hydraulic line and
unbolting the cylinder from the backplate.
Attempting to overhaul a leaking cylinder is
unlikely to be satisfactory, even if spare parts
are available.
1Chock the front wheels, then loosen the
rear wheel bolts, raise the rear of the vehicle
and place it securely on axle stands. Remove
the rear wheels and release the handbrake.
2Remove the drum retaining screw (see
illustration)and remove the drum. If the drum
is stuck to the hub, spray the area between
the hub and the drum with penetrating oil
(see illustration). If the drum still won’t come
off, the shoes have probably worn ridges into
the drum, and will have to be retracted. Insert
a narrow flat-bladed screwdriver through one
of the holes in the hub flange (see
illustration)and back off the adjuster wheel
until the drum can be removed.
3Inspect the drum for cracks, score marks,
deep scratches and hard spots, which will
appear as small discoloured areas. If the hard
spots can’t be removed with emery cloth or if
any of the other conditions exist, the drum must
be taken to a specialist to have the drum
resurfaced. Note:Professionals recommendresurfacing the drums whenever a brake job is
done. Resurfacing will eliminate the possibility
of out-of-round drums. If the drums are worn so
much that they can’t be resurfaced without
exceeding the maximum allowable diameter
(which is cast into the drum) (see illustration),
then new ones will be required. At the very least,
if you elect not to have the drums resurfaced,
remove the glazing from the surface with emery
cloth or sandpaper, using a swirling motion.
Braking system 9•7
6.2b If the drum is stuck to the hub, apply
penetrating oil around the hub/drum area,
and give it a few minutes to loosen up
any rust6.2a Removing the drum retaining screw5.6d If a rear disc still sticks to the hub,
insert a thin, flat-bladed screwdriver
through the hub flange, rotate the
starwheel on the handbrake adjusting
screw, and contract the handbrake shoes
(disc removed for clarity)
6.3 The maximum allowable inside
diameter of the drum is cast into the drum
6.2c If the brake shoes have worn a
groove in the drum and it won’t come off,
insert a thin flat-bladed screwdriver
through one of the wheel bolt holes in the
flange, and loosen the automatic adjuster
mechanism (for the sake of clarity, the
drum has already been removed in this
photo, and the screwdriver is being
inserted underneath the flange instead of
though a wheel bolt hole)
9
If the front disc is stuck, on
some discs it is possible to
thread two or three bolts into
the holes provided and
tighten them. Alternate between the
bolts, turning them a couple of turns at
a time, until the disc is free.

friction surfaces of the brake shoes or
drums.
12Make sure the adjuster assembly is
properly engaged with its respective notch in
the handbrake lever.
13When refitting the automatic adjustment
mechanism, fit the lever on the shoe first (see
illustration), then hook the lower end of the
spring onto the lever and the upper end into
its hole in the front shoe (see illustration).
14When you’re done, the brake assembly
should look like this (see illustration). Now
proceed to the other brake.
15When you’re done with both brakes, refit
the brake drums.
16If the wheel cylinder was renewed (see
Note 2), bleed the hydraulic system as
described in Section 16.
17Depress the brake pedal repeatedly to
actuate the self-adjusting mechanism. A
clicking sound will be heard from the brake
drums as the adjusters take up the slack.
18Check the handbrake adjustment (Sec-
tion 11).
19Refit the wheels and bolts. Lower the
vehicle to the ground, and tighten the wheel
bolts to the torque listed in the Chapter 1
Specifications. Check the operation of the
brakes carefully before driving the vehicle in
traffic.
7 Master cylinder-
removal and refitting
3
Warning: Brake fluid is
poisonous. It is also an effective
paint stripper. Refer to the
warning at the start of Section 16.
Note: Although master cylinder parts and
overhaul kits are available for most models, we
recommend fitting a new or overhauled
master cylinder complete. It will take you more
time to overhaul the master cylinder than to
renew it, and you can’t even determine
whether the master cylinder is in good enough
condition to overhaul it until you have
dismantled it. You may very well find that itcan’t be overhauled because of its internal
condition.
Removal
1The master cylinder is connected to the
brake vacuum servo, and both are attached to
the bulkhead, located on the left-hand side of
the engine compartment (see illustration).
2Remove as much fluid as you can from the
reservoir with a syringe.
3Place rags under the line fittings, and
prepare caps or plastic bags to cover the
ends of the lines once they are disconnected.
Caution: Brake fluid will damage
paint. Cover all body parts, and
be careful not to spill fluid during
this procedure.
4Loosen the union nuts at the ends of the
brake lines where they enter the master
cylinder. To prevent rounding off the flats on
these nuts, a split ring (“brake”) spanner,
which wraps around the nut, should be used.
5Pull the brake lines away from the master
cylinder slightly, and plug the ends to prevent
dirt contamination and further fluid loss.
6Disconnect any electrical connectors at the
master cylinder, then remove the nutsattaching the master cylinder to the brake
servo. Pull the master cylinder off the studs,
and lift it out of the engine compartment.
Again, be careful not to spill fluid as this is
done. Discard the old O-ring (see illustration)
between the master cylinder and the servo
unit.
Warning: The O-ring should
always be renewed. A faulty O-
ring can cause a vacuum leak,
which can reduce braking performance
and cause an erratic idle.
Bleeding procedure
7Before fitting a new or overhauled master
cylinder, it should be bled on the bench.
Because it will be necessary to apply pressure
to the master cylinder piston and, at the same
time, control flow from the brake line outlets, it
is recommended that the master cylinder be
mounted in a vice. Use a vice with protected
jaws, and don’t clamp the vice too tightly, or
the master cylinder body might crack.
8Insert threaded plugs into the brake line
outlet holes. Tighten them down so that there
will be no air leakage past them, but not so
tight that they cannot be easily loosened.
9Fill the reservoir with brake fluid of the
recommended type (see “Lubricants, fluids
and capacities” in Chapter 1).
10Remove one plug, and push the piston
assembly into the master cylinder bore to
Braking system 9•9
6.14 When you get everything back
together, this is how it
should look! 6.13b . . . then hook the lower end of the
spring onto the lever as shown; stretch the
spring, and hook the upper end into its
hole in the handbrake shoe6.13a Refit the automatic adjuster lever
first - make sure it’s properly engaged with
the notch in the front end of the
adjuster mechanism . . .
7.6 Always renew the O-ring (1) - groove
arrowed - between the master cylinder and
the brake servo
7.1 To remove the master cylinder, unplug
the electrical connector (top arrow),
disconnect the brake fluid hydraulic line
fittings (lower right arrow, other fitting not
visible in this photo) and remove the two
master cylinder mounting nuts (lower left
arrow, other nut not visible in this photo) -
5-Series master cylinder shown, 3-Series
similar
9

expel the air from the master cylinder. A large
Phillips screwdriver can be used to push on
the piston assembly.
11To prevent air from being drawn back into
the master cylinder, the plug must be refitted
and tightened down before releasing the
pressure on the piston assembly.
12Repeat the procedure until brake fluid free
of air bubbles is expelled from the brake line
outlet hole. Repeat the procedure with the
other outlet hole and plug. Be sure to keep the
master cylinder reservoir filled with brake
fluid, to prevent the introduction of air into the
system.
13High pressure is not involved in the bench
bleeding procedure, so the plugs described
above need not be refitted each time the
piston is released, if wished. Instead, before
releasing the piston, simply put your finger
tightly over the hole to keep air from being
drawn back into the master cylinder. Wait
several seconds for brake fluid to be drawn
from the reservoir into the piston bore, then
depress the piston again, removing your
finger as brake fluid is expelled. Be sure to put
your finger back over the hole each time
before releasing the piston, and when the
bleeding procedure is complete for that outlet,
refit the plug and tighten it up before going on
to the other port.
Refitting
14Refit the master cylinder (together with a
new O-ring) over the studs on the brake servo,
and tighten the mounting nuts only finger-tight
at this time.
15Thread the brake line fittings into the
master cylinder. Since the master cylinder is
still a bit loose, it can be moved slightly in
order for the fittings to thread in easily. Do not
strip the threads as the fittings are tightened.
16Tighten the brake fittings securely, and
the mounting nuts to the torque listed in this
Chapter’s Specifications.
17Fill the master cylinder reservoir with fluid,
then bleed the master cylinder (only if the
cylinder has not already been bled) and the
brake system as described in Section 16.
18To bleed the cylinder on the vehicle, have
an assistant pump the brake pedal severaltimes and then hold the pedal to the floor.
Loosen the fitting nut to allow air and fluid to
escape, then tighten the nut. Repeat this
procedure on both fittings until the fluid is
clear of air bubbles. Test the operation of the
brake system carefully before returning the
vehicle to normal service.
8 Brake vacuum servo-
check, removal and refitting
3
Operating check
1Depress the brake pedal several times with
the engine off, until there is no change in the
pedal travel.
2Depress and hold the pedal, then start the
engine. If the pedal goes down slightly,
operation is normal.
Airtightness check
3Start the engine, and turn it off after one or
two minutes. Depress the brake pedal several
times slowly. If the pedal goes down further
the first time but gradually rises after the
second or third depression, the servo is
airtight.
4Depress the brake pedal while the engine is
running, then stop the engine with the pedal
depressed. If there is no change in the pedal
travel after holding the pedal for 30 seconds,
the servo is airtight.
Removal and refitting
5Dismantling the vacuum servo requires
special tools, and cannot be performed by the
home mechanic. If a problem develops, it is
recommended that a new unit be fitted.
6Remove the master cylinder as described in
Section 7.
7Disconnect the vacuum hose from the
brake servo.
8Working in the passenger compartment,
remove the glovebox and lower left-hand trim
panels.
9Remove the clip and clevis pin to
disconnect the pushrod from the cross-shaft
lever (right-hand-drive models) or brake pedal(left-hand-drive models) (see illustration). On
left-hand-drive models, also disconnect the
brake pedal return spring.
10Remove the four mounting nuts (see
illustration)and withdraw the servo unit from
the engine compartment.
11Inspect the small foam filter (see
illustration)inside the rubber boot on the
pushrod. If the filter is clogged, it may affect
the servo’s performance. To clean the filter,
wash it in a mild soapy solution. If it’s still
dirty, renew it.
12Refitting is the reverse of the removal
procedure. Tighten the brake servo mounting
nuts to the torque listed in this Chapter’s
Specifications. Before you slide the boot into
place over the servo pushrod air filter, make
sure the notches in the filter offset the notches
in the damper by 180 degrees.
13On 3-Series models, adjust the basic
setting of the pushrod’s threaded clevis until
the dimension is correct (see illustration).
When the basic setting is correct, tighten the
locknut, then adjust the brake pedal travel and
9•10 Braking system
8.13 On 3-Series models, adjust
dimension A (the distance between the
middle of the brake lever and the
bulkhead/”firewall”) by loosening the
locknut (1) at the pushrod clevis (2) and
turning the threaded part of the pushrod
until dimension A matches the dimension
listed in this Chapter’s Specifications.
When the basic setting is correct, tighten
the locknut, then adjust the brake pedal
height and the stop-light switch
8.11 An exploded view of a typical servo
pushrod assembly
1 Boot 2 Holder 3 Damper 4 Air filter8.10 Remove the four mounting nuts
(arrows) and withdraw the servo unit from
the engine compartment
(left-hand-drive model shown)
8.9 Disconnect the brake pedal return
spring, then remove the clip and clevis pin
(arrows) to disconnect the pushrod from
the brake pedal (left-hand-drive models)

the stop-light switch (see Section 13). Note:
On right-hand-drive models, the brake pedal
in on the right-hand side of the vehicle, and is
connected to the left-hand side by a cross-
shaft. The adjustment is carried out on the
pushrod at the left-hand side, but the
dimension is measured at the pedal on the
right-hand side.
14On 5-Series models, adjust the brake
pedal height and the stop-light switch (see
Section 13).
15Refit the master cylinder (see Section 7)
and attach the vacuum hose.
16Carefully test the operation of the brakes
before returning the vehicle to normal use
9 Hydraulic brake servo-
description, removal and
refitting
3
Warning: Brake fluid is
poisonous. It is also an effective
paint stripper. Refer to the
warning at the start of Section 16.
Description
1On 5-Series E28 (“old-shape”) models, a
hydraulic brake servo system is fitted. The
servo unit, located between the brake pedal
(left-hand-drive) or cross-shaft lever (right-
hand-drive) and the master cylinder, is
operated by hydraulic pressure generated by
the power steering pump. When the engine is
running, the power steering pump supplies
hydraulic pressure to a power flow regulator/
accumulator. The regulator/accumulator
stores and regulates the pressure to the
hydraulic brake servo. When you press the
brake pedal, the pressure in the servo helps
actuate the master cylinder, reducing pedal
effort.
2The hydraulic brake servo cannot be
overhauled; if it fails, a new one must be fitted.
Testing the system requires special tools, so
even fault diagnosis is beyond the scope of
the home mechanic. If the system fails, take it
to a dealer service department or other
qualified garage for repairs.
Removal and refitting
3With the engine off, discharge the hydraulic
accumulator by depressing the brake pedal
20 times or more.
4Remove the master cylinder (see Section 7).
5Clean the area around the return and
supply line fittings, then disconnect them.
Plug the lines, to prevent dirt from entering the
system, and to prevent further fluid loss.
Caution: Even a particle of dirt
can damage the servo, so be
extremely careful to prevent dirt
from entering the system while
the lines are disconnected.
6Working from inside the passenger
compartment, remove the lower left trim
panels above the brake pedal (left-hand-drive
models) or glovebox and trim (right-hand-drive models). On left-hand-drive models, also
disconnect the pedal return spring.
7Prise off the retaining clip, and disconnect
the pushrod from the brake pedal (see
illustration 8.9) or cross-shaft lever.
8Remove the four mounting nuts and
remove the brake servo (see illus-
tration 8.10).
9Refitting is the reverse of removal. Tighten
the hydraulic lines to the torque listed in this
Chapter’s Specifications. Note:Don’t try to
tighten these fittings without a torque wrench.
If they’re loose, they can leak, which can affect
system operation; if they’re tight, they can be
damaged, and they’ll also leak. You’ll need a
crowfoot-type split ring (“brake”) attachment
for your torque wrench to tighten the fittings
properly.
10When you’re done, bleed the brake
hydraulic system (Section 16) and adjust the
brake pedal travel and the stop-light switch
(see Section 13).
10 Handbrake cable(s)- renewal
2
1Peel back the boot at the base of the
handbrake lever, and remove the handbrake
cable adjusting nut (see illustration)which
also secures the cable to the handbrake lever.There are two cables - one for each rear wheel
- and a nut for each cable. On some models, it
may be necessary to remove the centre
console completely for access.
2Raise the vehicle and support it securely on
axle stands.
3Remove the rear brake drum (see Section 6)
or rear brake disc (see Section 5).
4On rear drum models, unhook the
handbrake cable from the lever on the rear
brake shoe (see Section 6). On rear disc
models, remove the handbrake shoes and the
actuator (see Section 12) and unhook the
handbrake cable from the actuator (see
illustrations).
5On rear drum models, pull the cable and
cable conduit (tube) out of the back of the
brake backplate, then detach the cable
conduit from the cable clips on the back of
the trailing arm (it’s easier to pull out the old
cable, and fit the new cable, with the conduit
straight instead of curved). On rear disc
models, it’s unnecessary to detach the cable
conduit from the brake backplate, but it’s a
good idea to detach the conduit from the clips
and guides securing it to the trailing arm, to
take some of the bend out of the conduit.
6Working from the wheel end of the cable
conduit, pull the cable out of the conduit (see
illustration).
7Lubricate the new cable with multi-purpose
grease, then insert it into the cable conduit
Braking system 9•11
10.1 Peel back the handbrake lever boot
and remove the relevant handbrake cable
adjusting nut (both arrowed)
10.6 Pull the cable out of its conduit;
before you refit the new cable, be sure to
lubricate it with multi-purpose grease10.4b . . . then remove the pin securing the
cable to the inner cam, and remove the
inner cam
10.4a To detach the handbrake cable from
the handbrake actuator on models with rear
disc brakes, pull on the outer cam and
disconnect it from the inner cam . . .
9