5 Series 1997 – 2004
(E39)
Cooling
System
Water pumps and thermostats are common
failure points, with occasional radiator issues.
The electronically controlled
thermostats are prone to failure and set the “Service Engine Soon”
warning. They can short
out internally and melt a section of the engine wiring harness on
the V8 cars.
Computer
Readout
The display in the instrument cluster is
prone to drop pixels, making it difficult or impossible to
read. This requires
replacement of the instrument cluster, which must be coded to the
car.
Plastic Trim Around Seat
Cushions
The
plastic trim around the seat base is fragile and easily broken, but
is fairly inexpensive. If you ignore this for awhile, it may
cause the connector to disconnect from the seat switch or break the
switch assembly, adding significantly to the cost of
repair.
Front Thrust
Arm Bushings
The rubber bushings, which isolate unwanted
vibration during braking, age much like the rear shock mounts. They start to develop small
tears and cracks, then progress to completely broken out of their
mounting. The normal
symptom is vibration in the steering wheel under light
breaking. Ignoring this
will result in uneven tire wear. Larger than stock tires /
wheels amplify the symptoms.
V8 Power
Steering Hoses
The power steering hoses on the V8s will
leak. The low pressure
hose can be repaired, carefully cutting the crimped on clamps and
replacing the flexible hose section. The high pressure hose
requires replacement and is a fairly expensive part which is in very
tight quarters.
V8 Valve
Cover Oil Leaks
The V8 valve covers leak around the inner
and outer gaskets. The outer gasket leak leaves a visible on trail
of oil on the head. An
inner gasket leak isn’t visible until the covers are removed from
the engine, exposing a lake of oil in one or more spark plug
wells. If enough oil accumulates in the plug well, it
sometimes shorts the plug, causing
misfires.
V8 Vacuum
Plate
There is a plate on the rear of the intake
manifold that provides crankcase ventilation. The internal diaphragm
fails, requiring replacement.
This involves removal of the intake manifold. The symptoms are rough idle,
sometimes a whistling noise, and a “Check Engine” light.
6 Cylinder
PCV Valve
The vacuum valve on these cars has a higher
failure rate than the one on the previous 3 Series. Its failure
causes rough idling and sets the Service Engine Soon
light.
Brake Light Bulb
Sockets
The contact tabs on the sockets corrode or
bend. These can
frequently be cleaned up.
Also, when the center bulb fails, the dash display shows it
as one of the corner lights. The socket for the third light
sometimes melts.
Window
Regulators
We have seen quite a few failures of
these.
Cup
Holders
Fragile and easily broken with large
cups.
Lower Front Wheel Well
Liners
Plastic liner in forward part of wheel well
which is easily broken by contact with curb or concrete parking
stops, but is fairly inexpensive. The passenger's side liner shields
the secondary air pump from water and road debris. If it is
missing water can get into the pump, damaging the bearings and
requiring replacement.
Cam Position
Sensor(s)
The position sensor(s) for the camshafts will go open, either
intermittently or completely.
If it fails completely, the engine won’t run. If intermittent, it will
die, then restart, run for a while, and repeat the cycle. It usually sets the “Service
Engine Soon” warning.
Thermostat
The thermostat on these engines is electronically controlled
and experiences a moderate failure rate. If it sticks open, the
engine doesn’t fully get to operating temperature. If it sticks shut, the
temperature rises rapidly and the vehicle needs to be stopped as
soon as safely possible, then towed in for repair. It may also be a
temporary failure, but should be replaced as soon as possible. These problems set the
“Service Engine Soon” warning.
ABS - ASC/DSC
Controllers
The electronic brain for the braking and
stability control systems has a fairly high failure rate. It
is an expensive part and requires coding to the
vehicle.
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