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The BMW E24 Six Series Coupe



Background

The E24 was indeed a worthy successor to the previous E9 3.0CS/i coupe. It was built between 1976 to early 1989 with fairly few body changes, perfection is difficult to improve on after all. The shark like nose of the E24 is still a thing of beauty even now, no BMW has ever been so distinctive. The E24 has huge presence.

It is often assumed that the E24 is the sportier version of the E23 seven series, this isn't so. The proven E28 5 series provided the chassis and many mechanicals for it slightly bigger brother.

There has never been a true successor to the E24, the eight series is a different type of car and is much more expensive. Rumours of a "new six" based on the E39 five series persist and this may emerge in late 2000 powered by a V8 engine.

Models

The first model was the rare 630CS which used the same engine as the 3.0CS, it can be spotted due to its very small rear bumper. The 630CSi followed in the US and then the 633CSi. The 628CSi was a budget model for europe which was introduced in late 1979. It was complemented by the excellent 635CSi. The awesome M6 24 valve model produced a whopping 286bhp and remains one of the most desireable BMWs ever.

US versions of this car suffered terribly from anti-pollution regulations which greatly reduced engine power. They also had awful looking huge impact bumpers and were heavier. As a result euro cars are much better performers than their US equivalents. This difference reached its climax in the US L6 version. This car had an extremely luxurious extra, ie was 450kg heaver, and yet only had a 182 bhp engine!

M6 Highline attracting attention at Knockhill.

The elegant 635 CSi.

My own '85 635CSi, I'll never sell it.

The shark like profile of the M6. Only 5,803 were made.


Engines

All E24s were based on the M30 "big six" engine. All were 12 valve units except the 24 valve M6. The 630 was the only non-injection engined model.

All 635 models were not born equal. In June 1982 the engine used was upgraded to the version from the seven series. This uses less fuel due to better computer control systems but has little power difference and is far more desirable.

Model Body styles Engine Produced
between
Weight
(kg)
Power / Weight
(bhp / 1000kg)
Final drive ratio
(inc. options)
Brakes
628CSi Coupe M30 79-87 1410 130 3.46 Disc/Disc ABS*
630CS Coupe M30 75-79 1460? 127? 3.45 Disc/Disc
630CSi Coupe M30 75-79 1460? 131? 3.45 Disc/Disc
633CSi Coupe M30 75-81 1495 134 3.25 Disc/Disc ABS*
635CSi Coupe M30 77-89 1430 152 3.07 / 3.45 (US) Disc/Disc ABS*
M6 Coupe S38 83-89 1500 191 3.73 Disc/Disc ABS
L6 Coupe M30 ? - 89 1560? 117? 3.25 Disc/Disc ABS

ABS was an option on early cars, not standard equipment. LSD was an option on most later models. Automatic cars are 20kg heavier.

See the engine details page for power figures. US power figures for this car were quite a bit lower than euro figures and the cars were around 85kg heavier as well.

Some euro manual cars had the dog leg close ratio gearbox with first gear on it's own and second, third paired next to fourth and fifth. Most post 1984 cars were automatics in europe unfortunately. Some early cars only had a 4 speed manual box or a three speed auto, later autos were 4 speed. Many drivers believe the auto takes the edge of the performance, late model manual cars are worth more.

The L6 was a luxury version only available in the US and in automatic form. In the UK it was called the 635CSi Highline and some manual cars were made. This car had a leather head lining, leather door skins, leather dashboard, etc.

Known Problems & Buying Tips

Body & Fittings

Sixes are very well made cars but even the youngest is now eleven years old. They rust, but it's not fatal. The biggest problem is the front wings. They have no inner splash gaurd except at the back (20 quid each and I'll bet yours need replacing) and this causes both the inner and outer wings to rust. They cost about 450 quid each but the trick is to order a wing from a pre-82 Six which is 100 quid cheaper and only lacks turn indicator holes! The inner wing can just be welded up.

The rear shock towers are a common weak spot in old BMWs but the Six isn't as bad as the 2002, worth a check though.

If the door drains clogg the bottom of the door will rust out. Rust can also startbehind the trim strips on the door where the metal is perforated but this can be stopped if caught.

If the sill drains clogg the sill will rust, they start at the back. A partial sill costs 320+VAT.

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.

BMW Mobile Tradition are now remanufacturing the kidney grills, badges and early rear spoilers.

Front bumpers and airdams are 1500 new and are becoming hard to find used. Pre-84 (roughly) cars have external fog lamps, after that they were built into the air dam. Chrome wing mirrors are also becoming hard to get I believe. The 82-87 style rubber spoiler is no longer available.

If the windows howl at speed don't be too alarmed. They are adjustable for stop height and angle but in the extreme new (expensive) window seals may be required. BMW Gummi Pfledge rubber restorer can help and is highly recommended.

If the rear electric windows are slow it's due to lack of use. Put them up and down a few times a day and they'll recover. With the sunroof on tilt they allow for excellent ventilation by the way.

Water leaks in the boot can be caused by failing tail light gaskets, the inner ones cost 40 quid each. Old BMWs tend to suffer from a bit of condensation in the boot.

The headlamp wash / wipe motors alsoways gunk up. Remove them (grilles have two screws hidden on the indside behind the indicator housing) and clean everything that moves. Control relay is hidden behind the indicator inside the inner wing.

A body pack with rear apron and sills isn't uncommon, personally I don't like it.

Engine

The Six has a very big heart, the wonderful M30 engine. It came in several forms on the earliest cars but most examples have the 2.8, 3.5 or S38 24 valve 3.5 wonderful perfect gorgeous highly desireable M-Tech version.

The 2.8 uses Jetronic-K injection and gives 182bhp. It's alright but you really want the full 3.5 for a higher number of grins per mile.

The 218bhp, 229lb/ft 3.5 used Jetronic-K injection until mid-82 when it got the excellent Bosch Motronic 1.x system. This does away with points, vacuum advance and all other such mechanical aids and uses a micro-processor to decide when to fire the coil and injectors. It's very reliable and was a real boon to fuel economy. I recently saw an '87 car with 160K miles on the original cap and rotor arm! A worn rotor arm (9 quid) can cause a loss of high end power and even a non-start situation.

One of the biggest causes of intermittent stalling on old BMWs is dying relays or dirty wiring. For peace of mind replace the ageing main, fuel pump and unloader relays for 10 quid a time. Also a good idea to unplug and clean all wiring connections and body grounds. Only proper Bosch spark plugs should be used.

BMW approve unleaded only in post 6/87 cars, in practice most poeple run unleaded on older cars too and I've never heard of pinking or valve seat problems. Expect almost 30mpg on the motorway if you have a lightish foot. This drops to 22-24 in fast country roads and 17 in heavy traffic. Tank holds 16 gallons and I've managed over 400 miles on a tank, pretty good for a 3.5 litre with 160K miles and much better than and Rover or Jaguar of the time.

The high pressure (3.0 bar) fuel lines don't last forever. Ten years of heat and vibration will have caused cracking inside. They should be replaced with the correct BMW hose (20 quid a metre) to avoid a fire hazard, at the very least trim 10mm off the end. Don't forget the biggest culprit for fuel smells, the 6" line from the fuel rail to the cold start injector. Best changed by someone with small fingers and a little Vaseline on the ends of the new hose.

Poor idling can have two causes. A sticking idle control valve can be cured with white spirit and a toothbrush. Vacuum leaks are harder to find but even the small hoses, such as the one to the top of the fuel pressure regualtor, can cause problems.

M20s and M30s have a reputation for eating camshafts. This isn't the case unless oil changes have been neglectd or the "banjo" bolts on the oil spray bar have worked lose. The head must be removed to change a bad camshaft so make sure any ticking noise isn't major expense. All M20s and M30s seem to have a small oil leak from the front of the block, live with it.

Overheating can cause the alloy head to warp. This may be caused by a bad viscous coupling leading to overheating in traffic. The 15 year old radiator (110 GBP) is often the real culprit though. The water pump is only 15 GBP, mechanical parts are not expensive as BMW made this engine from 1968-1993! Non-UK cars with air conditioning use a two speed fan in front of the radiator, this can be a further cause of overheating in traffic.

If the engine seems tilted forwards or out of line with the air flow meter housing suspect failing frount engine mounts, not expensive.

Alternator rubber mounts fail around 130K, costs pennies and takes an hour to fix. Circlip pliers are handy.

Despite all this the M30 is a very reliable engine. I know of one in Canada with 660K miles and only one top end rebuild at 350K. It's chain driven and unless it becomes noisy the chain will last the life of the engine.

The 286bhp S38 24 valve DOHC engine is derived from the 1979-81 M1 supercar. It has six throttle bodies and I'd happily swap my fiance for one. It's very reliable indeed and is a huge tribute to Paul Rosche it's designer. Many people advise a new timing chain at 100K miles but MW have no such policy. This is an expensive job and unless the car has a lot of track time many owners leave it unless it gets noisy.

Transmission and Drivetrain

Manual Sixes could have a four speed (early cars), five speed overdrive or five speed dog-leg close ratio box which was standard on the M car. All are very reliable. At very high mileages the shift can become sloppy, this is cured by new bushings for the linkages. Don't worry about a little noise at idle when the oil is fully warmed.

Clutches last well but hydraulics can be tricky to bleed. The clutch should feel pretty stiff but if it's VERY stiff then one of the fork arms may have snapped.

The infamous ZF 4 HP 22 E/H automatic tansmission is another sotry. Early models had a three speed box, this became four speed and eventually had electronic control and a Sport/Economy/Manual switch next to the gear lever.

Check the fluid with the oil (Dexron II or III) warm and the engine running or you'll get a reading which can be way out. The fluid should be clear and not burnt. It must be changed every 30K or else. Failure to change the fluid means a new tranny around 150K miles so insist on proof. If it's not been changed for a long time then leave it. Changing it now will let all sorts of crud circulate back into the tranny and wreck it, this is why my own car is now a manual. There is also a filter screen under the tranny which should be changed every 60K, a good chance to check and clean the magnets in the drain pan too.

Never ever rev an auto Six at high rpm in park or neutral. This will cause over pressure on the A clutch pack and burn it out, time for a new trany. A pressure relief hole was added in the late 80's to reduce the problem.

Vibration under acceleration means it's time for a new centre bearing which isn't expensive. Other drive shaft wibrations can be caused by worn flex discs at either end. Post 82 cars had a more robust design.

Many cars had limited slip diffs fitted, these have an S or Z in the part number tag. Several ratios were used over the years and early cars had a different design. It's worth checking the diff mounting on early cars but to be honest the diffs are very reliable.

Brakes

Pre-82 cars had four pot front calipers and vented discs all round. Post-82 cars have the same single piston front caliper as E28 five series (69 quid each) and solid rear discs. M cars have fout pot brakes just like the M5's. PAGID pads dust a bit but are good value (10 GBP) and very effective. Discs for 20 quid, told you mechanicals were cheap.

Watch for vibration when braking very hard from 70mph. This can mean worn tie rods, centre tie rod, control arm bushings or warped discs.

The brakes use a Citroen style hydraulic accumulator affectionately known as "the Bomb" due to it's appearance. I once had a power steering pump drive belt snap at 100mph. The residual pressure in the bomb kept the brakes working for ten times of country roads. If the bomb fails it can result in a very hard brake pedal and dangerously poor emergency stop performance.

Check the ABS light glows yellow and then goes out when the engine starts. Many owners will remove it to hide dodgy ABS (ask me how I know). ABS faults are often caused by rusting stators on the wheels. The front ones are built into the wheel bearings (45 GBP) the rear are separate (22GBP).

Seized rear brakes can be due to collapsed rear brake hoses.

Steering

Expect some play in the steering, it's just a consequence or not using a rack and pinion system. It can be adjusted out a little. Power steering isn't overdone so don't be surprised if the steering seems a little heavy.

If the steering goes hard under full lock cornering it's time for a new filter in the bottom of the ATF reservoir.

The steering box mounts to the front subframe. The mounting isn't as strong as it could have been and has been known to crack.

Suspension & Wheels

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, this was the same design all round as the E28. It handles very well and is easy to steer on the throttle giving a rewarding and entertaining drive.

Post '87 cars sometimes had rear self levelling suspension. If this goes haywire it's best to replace it with standard shocks and springs.

Rear subrame rubber bushings perish with age and cause the car to wander. Not that dear to replace.

Early Sixes have 14" alloys. These gave way to the new TRX style. Good in their day but expensive and outdated now. 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.

Interior

Almost all cars have leather but early models often had velour. 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, they are a really nice design.

I'd avoid seats with electric adjustment. They weigh a LOT more and are expensive to fix if they break. The headrest adjustment tends to be the most fragile.

If the heater fan only works on full speed it's transistor is shot, not uncommon. The A/C has a separate fan behind the centre console. A/C adds about 50kg to the cars weight and removes the centre storage bin.

Seat mountings can crack slightly around the bolts and need welding.

The backlight on the onboard computer often dies. On a right hand drive car you can remove the stereo and replace the bulb unit with a pair of long nose pliers. On a left hand drive model you'll need to remove the centre console, I found this out the hard way.

It's not uncommon for the heating to go haywire. Often it's the heater control valve showing it's age. It's easy to replace but try to buy just the innards as the whole unit it 70 quid. If that's not it then check the wiring to the heater sensors in the heater core and above the driver's foot.

If the interior light delay doesn't work try the sensor in the driver's door handle. This door lock should also be heated when you pull the handle up.

If the tachometer doesn't work or the service indicator lights are all screwed up it's time for repairs. Don't pay 160 quid for a new SI board, get a pair of PCB mounted Varta NICAD batteries and solder them into the dash for a tenner. Some people use the SI lights for remote mounted radar detectors.

Model History

The Six started life in 1976. Earliest examples were built by Karmann.

1978 - Seven series front suspension Nylon fnex discs on driveshafts 1982 - The big upgrade! Better suspension, less weight, better electronics, new intake manifold, nicer dash, ABS,etc. mid'87- The next facelift. More modern looking bumpers, some detail changes, top mounting oil filter, ellipsoid headlamps. 1989 - Last car made in February, about 80,000 made.

Owning One

Regular and preventative maintenace is the key. Avoid a poorly maintained car. Feed the leather Neatsfoot and buy some Zymol, especially their glass and vinyl cleaners.

Give the car a strong dose of Redex then change ALL the fluids when you buy the cars, ATF, brakes, gearbox, engine, final drive, coolant, etc. Gets bits from Euro Car Parts or German and Swedish, they are half the price of the dealer.

Do a pre-winter rust inspection every year.

Most Six owners drive them every day so don't expect to find a low mileage example. These things were meant to be driven and enjoyed.

Modifications

The suspension is a good compromise but can be lowered up to 25mm, more results in excess negative camber at the rear. Stiffer anti-roll bars are also available. A strut brace is a good idea if the suspenson has been stiffened. Get the E28 brace from Demon Tweeks for 85 quid.

Ditch the TRXs for 16" alloys and modern tyres. 17" wheels are a bit much, they put a lot of strain on old rubber bushings.

If they fail replace the control arm bushings with milled down 750i bushings, Dinan sell them pre-milled.

E32 750i front brakes and E34 M5 rears are a good bolt on upgrade. 750i master cylinder is a nice upgrade too.

The euro engine is great, not worth modifying. The US unit lost 36bhp and has a lower compression ratio, a Jim Conforti chip helps.

These cars can be converted from auto to manual. You need the box, driveshaft, flywheel, pedal box and a few other bits. I've done this and like the result. The auto is better if you only do town and motorway work and has a lovely kickdown.

Links

Join the Big Coupe Groupe for all your E24 needs!

The another excellent Six series page is here.