BMW E34 Five Series - Mechanicals

Engines

	M20 Six cylinder 12 valve 2.0 and 2.5
	M21 Six cylinder diesels 2.4
	M30 Six cylinder 12 valve 3.0 and 3.5
	M40 M43 Four cylinder 8 valve 1.8
	M50 Six cylinder 24 valve 2.0 and 2.5
	M51 Six cylinder turbo diesel 2.5
	M60 First modern V8 3.0 and 4.0
	S38 Six cylinder 24 valve 3.6 and 3.8

 

M40 was used in the 518i until the M43 replaced it. M40 cars have a distributor, M43s have a coil pack so are easily spotted. The M43 used a timing chain instead of the belt found on the M40.

The 12 valve M20 was used on early 520i and 525i's. Spotted by the large silver curved intake manifold. 24 valve M50s had a black plastic manifold. M50 520i and 525i's were later upgraded to M50TU with single VANOS. TU's can can be spotted by the mug sized protrusion in front of the intake cam cover.

M21 diesel was used in the 524td. The M51 diesel was used in the later 525td and 525tds. The td didn't have an intercooler. M21s were never sold in the UK or USA.

M30 3.0 and 3.5 were used in the early 530i and the 535i. Engine size is stamped prominently on the intake manifold.

M60 V8's were used in the later 530i and the 540i.

S38 3.6 and 3.8's were used on the M5. The 3.6 has a distributor, the 3.8 has one coil per cylinder.

Some early models had the battery in the engine bay but it was later moved under the rear seat.

It's a little know fact that early ASC+T traction control was available! On the 535i M30 this took the form of a "fly by wire" electronic throttle body taken from the 850i V12. Our Alpina B10 3.5 has this option and I remember it once cutting in very nicely on a wet corner.

 

Suspension

All E34s had the same basic suspension with Macpherson struts at the front and semi-trailing arms at the rear. Unlike the E36 at both ends the shocks are mounted inside the springs. Front and rear anti-roll bars were always standard. The system wasn't that different from the older E28 and as such could be prone to losing the back end in bad weather.

Some E34s had self leveling suspension, most notably tourings. These days if it gives any trouble replace it with normal springs and shocks. The hydraulic pump sent pressure to the rear of the car.

Pitman arms, often called dog bones, were used to prevent side to side motion of the rear trailing arms. If your suspension wanders this may be a cheap and easy fix. The rear subframe is held to the body by a pair of large rubber bushings, these don't last forever and can be another cause of wandering.

Semi-trailing arm systems will have their geometry compromised by overly lowering the car, 25mm would be my limit. Unlike the E28 a front strut brace is probably overkill for a modified car as the body is much stiffer.

Nurburgring active suspension could be fitted to the M5. There were two versions, one with a setting control in the cabin and a simpler one with no driver input. The control module was under the back seat.

The suspension on the 525iX four wheel drive model doesn't use all the same components as the rear wheel drive cars and sits slightly higher.

Steering

All E34s used power assisted worm and sector steering rather than rack and pinion. The steering box is mounted on the same side of the car as the steering wheel, the other side has an idler arm. A centre drag link joins the steering box arm and idler arm whilst tie rods connect the ends of the drag link to the wheel hubs. If the system has play in the centre it can sometimes be adjusted out, but normally a new steering box is the only solution.

There are numerous bushings and bearings in this system and wear in any of them can cause problems, especially with wheels larger than 17" or wide tyres. The easiest way to check for play is to brake hard from speed and watch for vibrations in the steering wheel.

The power steering fluid reservoir is plastic on these cars and has a built in filter screen at the base. This filter can be flushed with spirit to clean but unlike the older cars it can't be replaced.

Servotronic steering was optional on some models, standard on later or more powerful cars. It provided speed-sensitive power steering, with lighter controls at low speeds, heavier steering at high speeds for improved stability. It used a control unit and solenoid in the steering box that adjusted assistance based on vehicle speed. Normal power steering was only engine-speed dependent. The Servotronic steering box had a small electronic control unit on the bottom and used a different hydraulic pump.

Brakes

A variety of disc sizes were used on E34s over the course of production but all offered exceptionally good performance for the time. They're bolt on compatible with the older five and six series and are often used as upgrades for those cars. Generally discs were 302mm front and 300 rear but quite a few thicknesses were used and not all front discs were vented.

The 525iX takes unique discs which are quite expensive now. The base 518i had rear drums on early models but went all disc later in production. M5s had 315mm discs all round, these were vented on the rear for the 3.8. M5 wheels were designed to force cooling air over the brakes. On the 3.6 this was done with a separate air deflector but the later 3.8 used the "throwing star" alloys with aerofoil spokes.

ABS was standard on all E34s.

 

Drivetrains

Most manual cars had a five speed box and whilst basically similar there were quite a few choices of ratio to suit different engines. A rare and highly desirable six speed box was used for the 540i Sport, it was taken from the E31 8 series. M5s had a Getrag 280 five speed until the arrival of the 3.8 when a six speed Getrag 420 replaced it.

A huge variety of final drive ratio were used as befits a model with power outputs ranging from 110 to 340bhp. It was quite common to find limited slip differentials on the 535i and other powerful examples and it could be specified as an option on others. E34s were never the best in snow and an LSD with snow tyres makes a massive difference.

But one E34 did excel in snow, the 525iX four wheel drive available in both saloon and touring. There were two versions here and details are on the xDrive page. Basically the early version used mechanical technology and the later early forms of traction control to manage the dynamics.

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TRX Tyres

Like the E28 and E24 six series many E34s were sold with TRX tyres. Ferrari, Jaguar and many others used TRX as it was seen to offer a very comfortable ride whilst providing good performance. 390mm TRX were to be found on 520i and 525i's with 415mm on the 535i. But the technology was soon bypassed leaving TRX owners struggling to find new tyres. By far the best option is to fit used 16" genuine BMW alloys with 225/55/16 tyres all round.