For some time, the rear wheels of BK02837 was a little too low. Although this filled the wheel-arches nicely, the ride was too harsh. This usually is caused by the pressure accumulators of the SLS-system. Each accumulator contains a membrane to regulate the pressure through the shock-absorbers. This membrane is made from rubber that is subject to wear and aging. At some point, the two chambers in the accumulators are connected due to which the shock-absorbers are subject to the full pressure of the SLS system that is fed by the PAS-pump at the front-left side of the engine.
The shock absorbers were replaced in 2006 at a considerable expense, but have been used for no more than 25k km since then so are still new. Besides, their retail price has increased to more than 700 Euro’s each; needless to say that I don’t want to take any risk of ruining them. Besides, I like the composed suspension of the E34 that despite using low-profile 17” tires isn’t overly harsh and thus offers some comfort on long distance trips without compromising on predictability. Next to originality, that was an important reason for me to stick to the OE suspension in July 2006.
The removal of the SLS-accumulators is rather straight forward. These are bolted to the body with three M6 bolts. The access to the rear-bolt is limited, especially on the left side where the exhaust limits space, but nothing that a few extension tools cannot solve. Care should be taken when disconnecting the ingoing and outgoing pressure lines. A simple half-open wrench won’t do as it doesn’t distribute the force evenly around the nut due to which it will just damage. Instead, I used a half-open hexagonal wrench, a much better tool for the job.
Since the pressure hoses between the SLS-accumulators and shock absorbers are replaced as well, I did not disconnect the outgoing connection directly on the accumulators, but on the shock absorbers instead. This requires two 17mm wrenches; one to secure the ingoing connector to the shock-absorber and the other two disconnect the nut from the pressure-hose. The right accumulator just drops out; the left one, requires lifting of the car to gain enough clearance between the exhaust and the drive-shaft.
After removal, the condition of the underlying body can be assessed, which apart from being a bit dirty is excellent. There is no rust and/or damage anywhere which is typical for a car that has never been used as a daily driver and also has never been subject to winter-usage.
Although not really necessary, I replaced the rubber mounts, bolts and nuts as well. The right accumulator is in place; the left one is still a to do item as well as the hoses.
Hopefully, this will solve the harsh ride, but I will know that for certain later this year. I would like to send the steering-box for a rebuild as well and since both systems are supplied with pressure by the same pump, I won’t fill the reservoir for the power-steering until-that is completed.
In between all this work, I found some time to fill the final drive with some new lubricant as well. On Limited slip differential’s such as used on the E34 M5, I prefer Castrol SAF-XJ which is rated with a viscosity of 75W140.
I used to buy this from the dealer, but at hefty price-tag of around 70Euro’s per litre. On ‘fleebay’, the same product is offered for just 12 Euro per liter, which is significantly less, but not always ‘fresh’ as being from recent production. Please note that Castrol recently relabeled SAF-XJ to
‘Limited Slip 75W140’. Despite the name-change, this is the same product.
