Cabrio knocking noise in rear right over bumps

[Zimmy318i]

When I drive over slight bump, there is an odd knocking noise from right rear...sounds like something hitting up against inside rear panel. Can't find anything loose in roof mechanics etc. No sound when I bounce rear suspension. Driving me crazy.

[Cloggy Saint]

Subframe bush? suspension top mount?

[Tzantushka]

Question: roof up or down or both?

As Cloggy has suggested, I would open the horseshoe cover for the roof compartment, pop off the square rubber bung and have a look at the strut top mounts.

[Zimmy318i]

Hi - thanks. I took a look at top mount and can't see anything amiss. Should I try tightening the nut to see? It's like slapping sound, something moving freely.

[Brianmoooore]

Hi - thanks. I took a look at top mount and can't see anything amiss. Should I try tightening the nut to see? It's like slapping sound, something moving freely.

Jack up the car, take the wheel off, then use a second jack to raise the hub a little (so that the damper isn't under tension), or place a block under the hub and lower the car a little to achieve the same effect, then grab hold of the damper near the top an see if there is any movement in any direction.

[Speedtouch]

Nothing to do with that ballast block they fit in convertibles, I suppose?

[Zimmy318i]

Hi - so definitely the top strut mount is wiggling/ loose. Is this a major fix ?
Many thanks!

[rix313]

Nope very easy

[Brianmoooore]

Nope very easy

Touring owners might not say that!

Undo the two 13mm nuts that hold the mount in place and the bolt at the bottom of the damper. Remove the damper and top mount together, and fit the new mount to the damper before refitting together.
Buy an E46 top mount, which is identical in appearance to an E30 one, but is considerably more durable.
Don't let the hub drop down when the damper is off - bad for the driveshafts.
There should be a paper gasket between the top mount and the body, but a bit of sealant will do instead.
The steel washer above the mount should curve upwards.
There MUST be a large steel washer under the mount. With OE dampers, this washer is part of the dust cover, but has to be added with some aftermarket ones.