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Buying and Maintaining an E24
Six Series
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Introduction
The youngest 6 is now a mighty decade and a half old,
mean terms for any motor vehicle. While BMW always built reliable and
resilient products capable of many years of service, it should be on
the agenda of any prudent owner or potential buyer to keep an eye out
for common problems and faults. In our guide, we have endeavoured to
bring to the surface the information needed to keep your six looking
and feeling the Bavarian style it emitted on the day it left the production
line.
Headstart Buying Advice
E24 6s are becoming rarer by the day, so getting a good one is going
to be directly related to the price you pay for it. Generally speaking,
prices on sixes are rising, so if you see a good deal make the commitment
now and save yourself in the hip pocket. The best models to purchase
remain the 635CSi and M635CSi, both are relatively recent and have innovations
not available on some of the earlier models. That aside, both have more
power and driving them is a real thrill. Earlier models are fine and
still hold their own, but try to avoid the 630CS, today, a model without
fuel injection is just not worth it. In addition, steer clear of anything
fishy, namely cars sold cheap without service history. Expect to spend
a little more on the six, as the better examples will always run better
and hold their value, while 'cheapie' 'bargains' will cost you more
in the long run. The 6 cylinder engine of the six series are premium
units but do have their problems after 100,000 miles, some need work
on the camshafts, valves and seals, so keep some money handy if you
buy one with rattles. The timing chain has also proved an issue after
150,000 miles, whose replacement could cost you ~ £2,500. Other
areas such as the suspension and exhaust take quite some punishment
over the years, so check these out. Rust is also a mitigating factor,
particularly dominant in the front wings, the bottom exteriors and the
exhaust system.
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Quick Buyer's Check-List
- Front body work should be checked for stone-chips, rust &
evidence of poorly repaired accident damage.
- Check that the service indicator & warning indicators are
operational.
Check the fan coupling isn't seized, the Motronic air-flow sensor
is working and that the head gasket is OK.
- Check that there is no black oil smoke, oil leaks on engine,
clattering camshaft, noisy cam chain or worn valve gear.
- Check for worn propshaft bearing, perished hoses, collapsed
offside engine mount (and subsequent forward tilted engine block
& misaligned air intake).
- Worn or noisy manual gearbox bearings, stiff gearshift action,
damaged propshaft/Gearbox couplings & loose or leaking deferential.
- Check for worn steering box, collapsed front & rear subframe
mounting brushes.
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Known Maintenances Issues for the E24 Six Series By
Category
Body & Structure
- RUST
The biggest problem is the front wings. They have no inner splash
guard except at the back and this causes both the inner and outer
wings to rust. They cost about £450 each (alternatively, order
a wing from a Pre-1982 Six for £100 cheaper, lacking only turn
indicator holes). The inner wing can just be welded up.
- REAR SHOCK TOWERS
Common area of weakness on the E24 6 series, worth an inspection.
- DOOR RUST
If the door drains become congested, this may cause rust to develop
on the bottom of the doors, eventually rusting out completely. Rust
can also start behind the trim strips on the door where the metal
is perforated. Treat with an anti-rust solution to prevent further
damage. Consider putty or silicon to repair any cavities.
- SUNROOF DRAINS
Check the four sunroof drains aren't rusty as they are very difficult
to fix if they leak. If they become clogged you'll get water in the
footwells. A bad windscreen seal can also cause this, as well as flooding
the DME in the process.
- MISC BODY PARTS
For replacement of badges, kidney grilles and early rear spoilers
for the six series, contact "BMW Mobile Tradition" who re-manufacture
selected items.
- HEADLAMP WIPE MOTOR
The headlamp wash & wipe motors commonly become congested. Remove
them (grilles have two screws hidden on the inside behind the indicator
housing) and clean the mechanical parts. The control relay is located
behind the indicator inside the inner wing.
- BOOT/TRUNK WATER RESISTANCE
Water leaks into the boot can be caused by failing tail light gaskets,
the inner ones cost £40 each. Older BMWs tend to suffer from
a bit of condensation in the boot.
- WINDOW SEALS & NOISE REDUCTION
If the windows make noise (e.g.. a howling) at high speed, it probably
indicates a problem with the door seals. They are adjustable for slope
height and angle but should you have to replace new seals can incur
a sizable expense.
- REPLACEMENT BUMPERS & AIRDAMS
Front bumpers and airdams are typically £1500 new and are difficult
to find used. Pre-84 cars have external fog lamps, after that they
were built into the air dam. Chrome wing mirrors are increasingly
rare. The 82-87 circa rubber spoiler is no longer available new.
- REAR ELECTRIC WINDOWS
Should an electric window only operate slowly (particularly rear windows),
the most probable cause is lack of use. Sustained use of the electric
windows should eventually rectify this problem.
Engine Issues
- FUEL INJECTION NOTES
Most engines equipped in the six series are of the M30 type, with
the most common variants are 2.8 and 3.5 litres in capacity. In addition,
the M-power S38 engine is standard in all 'M' versions. The 2.8 uses
Jetronic-K injection to give 134kW of power while the 3.5 edition
used Jetronic-K injection preceding 1982, when Bosch Motronic 1.x
systems became standard. The Bosch system makes obsolete points, vacuum
advance and other mechanical aids, using a microprocessor to fire
and coil injectors. This system heightened reliability and improved
fuel economy. Obviously, if you can, choose a Bosch model or ensure
that the Jetronic-K system is looked over regularly.
- RELAY & WIRING MALFUNCTION: STALLING
Common difficulties exist in older sixes where the relays reach the
end of their lifespan or the wiring systems become dirty. This, in
some cases, can cause the engine to stall on regular occasions. To
ensure reliability, replace original fuel pump, main, and unloader
relays. Consider unplugging and cleaning all wiring systems. Use only
Bosch spark plugs.
- FUEL LINE REPLACEMENT
The high pressure fuel lines will eventually need replacing. More
than a decade of heat and vibration will have had its toll on the
average car, and the fuel lines especially. Replacement should be
attempted only with the correct BMW hose line.
- POOR IDLING
Two major causes, a seized or sticking idling control valve or vacuum
leaks. The first is solved with some white spirit and a small brush.
Check out the hose at the top of the fuel pressure regulator which
can be a common culprit for vacuum leaks.
- CAMSHAFT COMPLICATIONS
Without proper care and maintenance, M30 engines are notorious for
wearing down camshafts. This shouldn't occur, as long as regular oil
changes have been routine or unless bolts on the oil spray bar have
worked loose. To repair, generally an expensive operation, the head
must be removed to replace the camshaft. You can detect problems with
the camshaft which typically gives itself away as a "ticking"
sound coming from the engine.
- OIL LEAKS IN M20/30 ENGINES
Most M20/30 engines have an extremely minor oil leak at the front
of the block. Typically it doesn't affect performance and need not
be rectified. It will become problematic should the leak be copious.
- ALTERNATOR MOUNTS
The rubber alternator mounts generally fail after 130,000 miles.
- OVERHEATING
Overheating may cause the alloy to 'warp'. Commonly the radiator and/or
water pump can be blamed for overheating problems. Today these parts
are relatively cheap. Cars (excluding UK models) with Air Conditioning
use a 2-speed fan in front of the radiator, which can cause the car
to overheat in heavy traffic.
- ENGINE ALIGNMENT
If the engine seems tilted forwards or out of line with the air flow
meter housing, suspect failing front engine mounts. Not generally
expensive to rectify.
Transmission & Drivetrain
- TRANSMISSIONS IN 6 SERIES UNITS
Manual sixes have a range of forms. Early examples can be found
with a four speed gearbox, while later units may sport a 5-speed overdrive
or 5 speed 'dogleg' close ratio gearbox (standard on M6). All gearboxes
were well designed and usually offer little complaint. Automatic sixes
were initially 3 speed units, later evolving into four speed and later
still emerged electronic control and a choice of "Sport",
"Economy" and "Manual" modes to suit the diverse
driver.
- HIGH MILEAGE
High mileage can cause the shift to become troublesome, new bushings
for the linkages generally solves this problem.
- CLUTCH RESISTANCE
Typically the clutch is fairly stiff and resistant to pressure, but
if it suddenly becomes excessively difficult to depress, one of the
fork arms may have failed.
- AUTO TRANSMISSION FLUID LEVELS
Always check the fluid with the engine running (oil warm) to ensure
an accurate reading. The fluid should appear clear and not burnt.
Transmission fluid must be replaced every 30,000 miles to ensure durability.
Failing to change the fluid may cause the unit to fail (at approx.,
150,000 miles). If you find an example of a badly deteriorated transmission
(due to failure to change the fluid), do not attempt to change the
fluid now as that may cause further damage (new debris will again
circulate around the system, shortening the unit's life further still).
Filters on the transmission should be changed every 60,000 miles.
- PARK & NEUTRAL PRESSURE ISSUES
"Reving" the engine at an extremely high rate of R.P.M.
in the positions "PARK" and "NEUTRAL" can cause
failure in early automatic transmission units. Such an action creates
pressure upon the A clutch pack, causing it to fail. If such a scenario
occurs, the whole transmission unit may have to be replaced.
- VIBRATION DURING ACCELERATION
This is generally caused by a worn centre bearing. Replacement is
inexpensive. Other drive shaft vibrations could be caused by worn
flex discs. Post-82 vehicles are less likely to suffer these problems.
Brakes
- NOTES ON BRAKING SYSTEMS
Pre-82 cars had four pot front calipers and vented discs all round.
Post-82 cars sport the same single piston front caliper as E28 five
series and solid rear discs. M cars have four pot brakes just like
the M5's.
- VIBRATION
Vibration when braking hard from speeds of approximately 120km/h can
indicate worn tie rods, centre tie rods, control arm busings and disfigured
discs.
- ABS WARNING LIGHTS
Check if the ABS light glows yellow and then goes out when the engine
starts. Many owners will remove it to conceal failing ABS systems.
ABS faults are often caused by rusting stators on the wheels. The
front ones are built into the wheel bearings the rear are separate.
- SEIZED REAR BRAKES
Can be due to collapsed rear brake hoses.
Steering
- NOTES ON POWER STEERING SYSTEMS
There will always be some resistance on the steering wheel, this is
usual as BMW didn't over emphasize the power steering capacity. It
provides what is necessary and doesn't overlap into the over-responsive
category.
- STEERING LOCK RESISTANCE
If the steering becomes excessively heavy on full lock, a new filter
in the bottom of the ATF reservoir should fix the problem.
- STEERING BOX MOUNT
The steering box is mounted to the front subframe. This mounting has
been known to crack due to a design fault.
Suspension & Wheels
- SUSPENSION NOTES
In 1978 the Six gained the front suspension upgrades of the E23 seven
series for better anti-dive performance. In 1982 the rear trailing
arms were angled to 13 degrees to improve road holding, matching the
E28's overall design. It handles very well and is easy to steer on
the throttle giving a rewarding and entertaining drive.
- REAR SELF-LEVELING IN POST 1987 VEHICLES
Post-87 examples were equipped with Rear Self-Leveling suspension,
on occasion it does malfunction. The most economical replacement choice
is standard shocks and springs.
- WHEEL NOTES
Early Sixes have 14" alloys. These gave way to the new TRX style.
Burns suggests the "Best idea is to run 16" wheels and 225/50ZR16
tyres all round, I like Fulda Extremos. Wheels from any five bolt
BMW fit except the E36 three series (wrong offset). New E39 five series
wheels need a hub ring to fit but the offset is OK." (See BURNS:
REF01)
Interior
- INTERIOR NOTES
Most Sixes were leather breeds, but some early models were decked
out in velour. Burns on the general interior commented, "The
Highline, called L6 in the USA, had leather seat backs, headlinging,
door skins, dashboard, and rear A/C with a cooler cabinet! Try and
get a car with rear headrests, [as] they are a really nice design."
(See BURNS: REF01)
- ELECTRIC ADJUSTMENT
Some have suggested the avoidance of a model with electric seat adjust,
citing common failure and expensiveness to replace. The headrest adjustment
appears to be the most prone to failure.
- HEATER FAN: ONLY OPERABLE AT FULL SPEED
If the heater fan only works on full speed: probably an expired transistor.
The A/C has a separate fan behind the centre console. A/C adds about
50kg to total weight and is optioned at the expense of the centre
storage bin.
- NON-DURABLE SEAT MOUNTINGS
Seat mountings may crack slightly around the bolts and require welding.
- FAULTY COMPUTER BACKLIGHT
The backlight on the on-board computer has been known to fail. Generally,
the expired globe can be replaced. Replacement procedures are different
for left and right hand drive cars. Right Hand Drive: Remove the stereo
and replace the bulb unit with a pair of long nose pliers. Left Hand
Drive: Remove the centre console to access the bulb unit.
- FAULTY HEATING SYSTEM
Not uncommon. Typically, the result of an old heater control valve.
Otherwise, check the wiring to the heater sensors in the heater core
and above the driver's foot.
ORIGINAL CREDIT ACKNOWLEDGMENT
Portions of this report owe an exclusive debt to John G. Burns &
his feature of the "E24 Six Series Coupe"
REFERENCES
REF 01 - The Unix Nerd's Domain, "The BMW E24 Six Series
Coupe", John G. Burns, Available: http://www.unixnerd.co.uk/e24.html
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