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Buying and Maintaining an E24 Six Series

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.

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.demon.co.uk/e24.html