Strut mount replacement on a BMW 5 Series like the BMW 535i is essential to the balance of steering and suspension. Failing strut mounts can cause poor drivability, noise, and in extreme cases can cause damage to the strut shaft. It is best to replace them as soon as they show signs of failure.
Replacement is pretty straightforward. A spring compressor tool will be required. There are several variations of spring compression tools. Whether you have springs or coilovers, choose one which fits your application.
A 3/8" and 1/4" socket set should suffice, preferably one with 10mm, 13mm,17mm sockets, a 19 or 22mm deep socket (depending on year of your E34), a short extension, and 13mm open end wrench if necessary.
Rear Strut Mounts
If you're planning to replace the rear strut mounts, you must remove the rear bench seat by lifting the lower cushion and removing the 4 plastic 10mm nuts securing the lower part of the backing (2 lower corners, 2 skibag/rear armrest location). Then release the rear left safety belt receptacle from its clip within the backing. If you are one of the lucky owners with rear headrests, you'll have to remove them. With the plastic nuts, headrests and receptacle out of the way, lift the backing to free it from the bottom then up to remove it. This should expose both rear mounts.
At this point you can go ahead break free the wheel bolts and raise the car in the rear. Remove the wheel(s) and remove the 22mm bolt securing the strut to the trailing arm and the 3 - 13mm nuts from the strut mount. You should now be able to remove the rear strut(s) from the car.
If the strut has been on the car for some time it will be a fight to free the lower shock eye sleeve from the trailing arm. There are a few tricks to getting it loose when seized into the trailing arm. One common trick is to wedge a pry bar between the shock and the trailing arm. Using a combination of force and saturating the area with WD-40 it will usually and literally pop right out.
Once loose and off the car, grab the spring compressor tool and compress the spring far enough to where you can remove the strut mount safely. Take your 19mm socket and remove the nut and large washer on the strut mount. Install the new mounts, and re-install the struts.
Front Strut Mounts
Before doing the front strut mounts, make sure your replacements match the worn ones. These vary per model year with a different strut shaft diameter. Removal of the front strut mounts or front strut guide supports is similar to the rear, however not as involved as the rear struts and removal of the strut is not necessary.
If you choose to remove the strut there are three 19mm bolts at the bottom of the strut which connect them to the steering plates. I suggest using a deep socket or a small extension, for one of the bolts sits behind the dust shield and can be a pain if the dust shield is bent or damaged. From there you can remove the caliper if you wish for the strut can be a little hefty with the calipers and rotors attached. I suggest tying the calipers up and away from the strut to allow room to work.
Front mount replacement is very similar to the rear mounts for you will need to use the spring compressor to lower the spring. To make things easier, disconnect the swaybar links from the stabilizer bar or the strut. This will allow you to tilt the strut out to remove the strut mount. With the new mount installed you can begin to button everything back up. Unlike the rear, front strut mount replacement does require a wheel aligned once complete. So make sure once your finished to set an appointment to have the alignment done.
New Strut Mounts
BMW utilized Lemforder and Sachs strut mounts in this vehicle, making the choice for replacement parts a no-brainer.
Late E34 Front: BMW Strut Mount Set (E34) - Lemforder (OEM) - 31331139437LX2
Early E34 Front: BMW Strut Mount (E34) - Corteco 31331134096
Rear: BMW Shock Mount Rear (E34) - Sachs 802-381
