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Like many BMWs, the Z3 M Coupe is prone to failure of the rear shock mounts. This failure becomes noticeable as a clunking rattle as the rear wheels go over bumps in the road. Replacing the rear shock mounts is a really easy job, and should take about 10 minutes a side.
Dead shock mount
Dead shock mount
Unfortunately, when they designed the M Coupe, nobody bothered to tell BMW's ace Trim Over-Engineering Team that you might want to replace either the shock or the shock mount as part of routine maintenance of a car. As a result, gaining access to the top mounts is a hellish job which takes about an hour if you know exactly what you're doing, and much longer if you're muddling through it without instructions.
The length of the job depends on how far you're prepared to bend bits of trim. If you don't mind some serious trim bending, I understand that this job can be done without removing the side carpets fully (bend them hard and work blind on the top mounts). This page explains how to do it with only modest bending. If you can't bear even this then you'll also be removing the seat belts, the whole of the B-pillar trim, and the centre divider piece with oddments tray.
It starts easily enough. Remove the rear floor cover. Remove the two screws holding in the front floor cover, and slide it back towards you. Remove the padding underneath it.
You need to get the piece of trim under the rear windows half-way out. Start at the C-pillar by removing the piece that holds the roller boot cover. A single screw holds this in. The piece behind this just pulls out - pull it straight towards the middle of the car. There's only one clip on the back of it:
C-pillar trim pieces
Back of C-pillar trim pieces
You should now see two screws at the rear of the next piece of trim. Take these out. You can now lift the trim a little and begin to see what you're up against. The carpet is held in by plastic clips, the front most of which is under the boot cover/net. There's a also a screw that you can't see yet below the B-pillar. You might get away with removing only the rear clips and bending the carpet (especially on the right hand side), but I wouldn't recommend it. You need to take that centre divider to pieces...
Two bits of trim on the left and right. Pull these straight up. The net is held in by two 10mm nuts on each side, now clearly visible through the window. Remove these and then the boot cover. Note that there's still another piece of trim screwed on top of those wretched under-window pieces that are blocking access to the carpet.
First remove the sub cover (if you've got a sub). There are plastic screws along the top at a really annoying angle. Once these are out, there are clips holding the bottom in. You'll want to take the speaker grille out so that you can pull the trim next to the clips to avoid breaking it. Same procedure for the CD changer, this time use the changer window to get your fingers close to the clips.
You'll now see that you need to get the two side pieces of the centre divider out. If you still weren't convinced that this is a big conspiracy against you, note that the small side pieces require the large centre piece to come out first. Fortunately, it only needs to be loose, not removed completely.
First, remove the carpet piece inside the oddments tray. This is held in by one of those quarter-turn plastic screw thingies. Below the carpet are two screws with large, oval washers. Remove these.
Now you need to get the screws along the front out. These have got soft plastic caps on them. I couldn't find a way of getting these off other than grabbing them with needle-nose pliers. This doesn't do them a lot of good, but they're cheap to replace (part 51181823474). Remove the caps and the screws.
With the centre piece loose, you should now be able to free the side pieces. First remove the screws by the window that are holding the side pieces in, and the screws that attach the side pieces to the centre piece. Now, lift the centre piece up a bit and push it forwards once clear of the side piece. The side piece should now just lift out.
Side divider screw
Side divider screw
With the side divider piece out, you can now get at the screw in the front of the carpet.
You can also lift the below-window trim up enough to get at the front top clip, although it's still a pain. Here are the clips that you're up against:
Front carpet clips
You need to get the pins out. I did this by prying with a butter knife until I could get needle-nosed pliers onto the shaft of the pin.
You also need to remove the tie-down points. Nothing's ever easy. The game here is the little piece of plastic covering the ugly screws. A very small flat screwdriver and needle-nosed pliers are the answer.
The carpet should now come free. With some care, the sound-proofing will follow, and you should be looking at the top mounts.
This is pretty straightforward. I recommend putting the rear wheels on ramps rather than using a jack / axle stands. If you do use a jack, you should support the rear wheel or trailing arm before removing the shock. The shock retains the trailing arm and you could damage the axles if you allow them to drop.
First remove the bolts hold the top mount in. Then remove the 18mm bolt at the bottom. This should be done up tight (77Nm, I believe). Support the shock as the bolt comes out. They're not heavy but they will be compressed when on the car.
When you remove the shock, you will look at the top mount and think, "why didn't they just put the studs on the inside and nuts on the outside?". Who knows, but others have acted on this thought already. Rogue Engineering have replacement shock mounts that do exactly this. Alternatively, it's been suggested that you can get a re-inforcement plate designed for the Z3 and just weld on studs from your old mounts.
Paul Warren 10:03:10 23-Dec-2014