BabyBimmerAfter looking at the lead photo for this article on
3-sehes BMW service tips, you might get the impres
sion that the owners of these cars are a bunch of
crybabies. Quite the contrary. What we do mean tosay is that the information contained in this article
is intended to keep your Baby Bimmer customers
(who just might happen to be baby boomers them
selves) happy and pacified.
BMW introduced their new 3-series line in 1984
as a replacement for the late lamented 320i. Over the
years since then, there have been a staggering vari
ety of BMW models beginning with the number 3.
We've seen the 318i with its four cylinder M10B18
engine come and go, then come back again with an
all new engine. And there have been several differ
ent "small" six cylinder 325 models, using either the
2.7 liter M20B27 "eta" engine or the later 2.5 liter
M20B25 engine.
Once you've decided which engine is in the en
gine bay, the rest should be easy. The original 318i
uses a Bosch L-Jetronic fuel system, while all 325
models have a Bosch Motronic engine management
system. The 318i only lasted for two years, so most
of our engine tips will deal with the more common
six cylinder 325 models. We'll note any differences
in this area where necessary.
All 3-series models, in both four or six cylinder
varieties, share the same basic body and running
gear design. Something of a rarity for a small car
today, 3-series BMWs still steadfastly cling to rearwheel drive.
Many of the performance and safety features
found on larger BMWs have been squeezed into the
3-series body style. You're likely to find ABS, an air
bag, a Check Control Panel, and some power acces
sories on a late model 325. This may be an entry
level BMW, but it's still a BMW.
All of this complexity hasn't seemed to affect
basic 3-series reliability. While electrical problems
aren't unheard of on these cars, they can usually be
solved using basic troubleshooting techniques. Look
for damaged or corroded wiring or wiring connec
tors to cause electrical problems more often than
actual component failures.
BMW revived the 318i last year with an all new
twin-cam, four cylinder engine with four valves per
cylinder. Service information about any problem ar
eas with this engine is still pretty scarce. An all new
re-bodied 3-series line is also scheduled for release
this year. We'll keep you posted before these newer
models start driftmg into your shop.
By The Numbers
We've arranged our 3-series information into
three loose categories. The first group of photos and
captions deals with several items you should be
aware of while performing basic 3-series mainte
nance. Using these tips will help you recognize prob
lems before they have a chance to cause your cus
tomer any inconvenience.
The middle group of photos covers several elec
trical tips to get you pointed in the right direction.
Then we'll finish up with undercar steering, suspen
sion, and brake information.
The 3-series BMW is a rugged piece of machinery
that's designed for use as an every day driver rather
than a pampered play toy. We hope the information
in this article will help your customers enjoy many
miles of trouble-free driving while making your life
a little easier in the bargain.
— By Callan Campbell
i
The six cylinder engine will bend valves if the timingbelt breaks. These belts can break before the recommended 60,000 mile change interval. Changing the
belt at least every four years or 50,000 miles shouldprevent expensive surprises like this. Also check for
water pump leakage during belt replacements.
Two timing belt lengths, several cam sprockets, andtwo belt tensioner designs have been used on the
six. Some of the earlier parts are no longer available.
Only parts marked "Z 127" should used. Later timing belts are one tooth shorter and slightly wider,and must be used with the later tensioner design.
Baby Dimmer
3
The stamped steel camshaft sprocket marked
"Schroth" installed on early sixes had a habit of
breaking loose from its center hub. A blue dot on the
thermostat housing and a round driver's door pillar
label with the number 14 punched out mean the
sprocket has already been replaced under warranty.
Worn rocker arm bushings and rocker shafts can
cause noisy valve train operation. Wiggle the rockers to check for excessive clearance. Rocker feet and
cam lobes may also wear on low maintenance en
gines. Always replace the rubber rocker shaft seals
at both ends of the head during valve adjustments.
7
The oil filter housing bottom cap is a spot to watch
for oil leaks on later 325s. A seal kit is available to
repair housing leaks. It's easier to remove the hous
ing first, then replace the seal with the housing held
in a vice. All housing seals should also be replaced
during reassembly to prevent other leaks.
Remove the radiator fan and fan clutch to reach the
six cylinder cap and rotor. This fan clutch tool slips
over the water pump pulley bolts to keep the pump
from turning. Then a thin 32 mm wrench is used to
loosen the left hand thread fan clutch nut. Now re
move the fan clutch, fan, and shroud.
6
The four and six cylinder engines both use an eccen
tric valve adjustment system. On a new engine, the
eccentric cam adjusting holes (arrow) will point
almost straight up. Start looking for worn valve train
parts if the adjuster is turned all the way around and
the clearance still isn't right.
8
Engine vibration may crack this exhaust system
mount at the rear of the transmission. Transmission
leaks may not be caused by a leaking output shaft
seal. Check the selector shaft seal directly above the
output shaft. Also make sure the shifter console
mount bolts at the top of the transmission are tight.
Baby Bimmer
9
Six cylinders also like to leak along the right edge of
the head gasket. There are several oil return pas
sages along this edge that drain oil from the head
back to the oil pan. Replacement head gaskets with a
printed seal around the oil returns are designed to
prevent leakage in this area.
Check for cracks in the short hose between the inlet
fuel hose union and the cold start injector. Other fuel
hoses may also harden and crack due to high
underhood temperatures. Replace damaged hoses as
necessary, using the correct hose clamps. Small fuel
leaks may go unnoticed until they cause an engine fire.
The six cylinder's thermostat housing elbow (arrow)
can loosen and cause an intermittent coolant leak.
Replacing the housing is safer than trying to glue the
loose elbow back into place. Remove the coolant
sensor, then loosen the fuel rail bolts to reach the
thermostat housing bolts.
Be careful when changing the gas filter on 318i and
early 325 models. The filter is mounted near the
starter and must be removed from below. It's very
easy to touch the starter's battery terminal with the
aluminum filter and risk more than a spark. The filter
was moved to the rear axle area on later 325 models.
Carefully inspect the area around the spark plugs
before removing the plugs. The plugs face downward
in the cylinder head, so a loose part could end up
dropping through the spark plug hole. Remove the
plug in the six cylinder exhaust manifold (arrow) to
check emissions ahead of the catalytic converter.
A faulty vacuum advance solenoid (arrow) on early
318i models may leak vacuum to the distributor at
idle, affecting advance operation. Early solenoids
receive manifold vacuum and battery voltage while
the engine is running. The control unit grounds the
solenoid to open the solenoid above idle speed.
Baby Bimmer
Later 318i models have a different distributor and
vacuum control solenoid. The updated solenoid con
trols a ported vacuum signal. So even if the solenoid
leaks, the timing can't advance at idle. The later
solenoid design must only be used with the revised
distributor and a ported vacuum source.
A no start condition at low outside temperatures on
325e models built before October 1985 may be
caused by a misrouted cable at the firewall-mounted
battery junction block. The cable (left arrow) should
be routed as shown, not connected to the terminal at
the opposite end of the block (right arrow).
The 318i and 1984-7 325 models have a separate idle
control unit to maintain the idle speed. A poor con
nection between the control unit and its harness con
nector may trick you into blaming the idle control
unit for idle speed problems. Plugging in a new con
trol unit may temporarily repair the loose connection.
A set of jumper leads with matching terminals
should be used for tapping into the diagnostic con
nector. Use a remote starter switch for valve adjust
ments by attaching the leads to terminals 11 and 14.
The second jumper set fits the black diagnostic
connector's smaller terminals on later 325s.
The black plastic idle control valves on 318i and
325e models can fool you because they lack an ex
ternal adjusting screw. These valves can be adjusted
by turning the small screw inside the valve. Shunt
into the control valve wiring with jumper leads to
measure the milliamp reading with a DVOM.
20
This large female connector at the A pillar is a good
place to check when diagnosing power window or
door lock problems. Water can get inside the con
nector and cause wiring corrosion. Corroded pin ter
minals can be replaced separately. The door harness
should be replaced if many terminals are damaged.
Baby Bimmer
21
The connector must be properly reinstalled after re
pairs or water will leak in again and spoil your work.
Slip the protective boot over the male door harness
connector first. Make sure the boot fits tightly over
the connector. Now reattach the male door connec
tor to the female connector at the A pillar.
A brake pad warning light that flickers or stays lit
(even though the pads aren't worn out) may be caused
by damaged brake pad wear sensor wiring. Sensor wir
ing often breaks inside the insulation. The open circuit
causes the warning light to come on. Someone has
already bypassed the damaged wiring to this sensor.
If the wiring is broken on the body harness side ofthe sensor connector, cut the body harness about an
inch away from the connector boot. Solder an old
pad sensor connector into the harness. Use heat
shrink tubing to cover the splice. Trim the harness
connector so it fits into the pad sensor connector.
Fuel pump noises may be caused by the transferpump inside the tank going bad, rather than a main
pump failure. The rubber boot connecting the trans
fer pump to the metal supply pipe may also split.
The leaking boot causes the main pump to suck air
when there's less than a third of a tank of gas.
Defective main and fuel pump relays can cause inter
mittent stalling problems. The relay closes, but pitted
contacts won't pass current through the relay. Tap
ping on the relay may cause the engine to stall. On six
cylinder models, the main relay powers the Motronic
control unit and the fuel pump relay windings.
The sealed front wheel bearings are normally
replaced as an assembly. Bearings and hubs are
available separately, however. If a new bearing is
installed inside a used hub, make sure the outer
bearing race fits tightly inside the hub. If not, the
race may turn inside the hub and ruin the bearing.
Baby Bimmer
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27
Check for sagged or broken lower control arm bush
ings (arrow) if the steering shudders when the brakes
are applied. Install new bushings with the arrow
pointing toward the notch on the arm. Grinding a
slight chamfer on one edge of the bushing will help
start it into the arm. Replace bushings in pairs.
Some brake pad compositions can also cause front
steering and suspension vibrations during braking.
Hard pads seem to transmit even slight rotor surface
variations to the steering wheel when decelerating
quickly with hot brakes. Worn suspension parts will
amplify these vibrations.
Mitchell On-Demand Repair Information System.
Circle No. 114 on Reader Service Card
Clunking noises from the rear suspension may be
caused by worn upper shock mount bushings. Worn
bushings let the shock wobble around over bumps. If
the clunking is ignored, the upper mount may dis
connect from the body and really make a racket. The
bushings are available without replacing the shocks.