rear driver's side knocking noise

[tim_s]

hi guys,
have a weird knocking noise from the rear right(ish) of my e30. sounds like i have a knackered bush, quite a lot like knackered top mount noise. i've already tried a spare shock and top mount in there but no change, also had it up on some ramps at a local garage who had a bit of a look and couldn't see anything astray. i've pulled all the trim, rear seats etc. out, hit various bits of the car to hear for noises, bounced on suspension etc but can't replicate the noise. only happens going over bumps. had a look at the expansion tank thing for the fuel in the wheel arch and that seems secure too. car handles fine. rear subframe and trailing arm bushes done a few years ago, so not out of the question, but seemed fine at the local garage and can't feel any movement anywhere. anyone any ideas of other things i could be looking at? made sure the zorst was clear of everything too, checked arb mounts etc... getting a bit frustrated now, think i may book it in somewhere but could do without the expense with all the engine rebuild bills i have at the mo!
cheers
tim

[TheDutch]

Tim,

Sounds like it's not the same as your problem, but I had a similar issue which turned out to be the exhaust knocking over bumps. The back box on my iS was held only by one strap instead of two, fixing this cured the problem.

Is your spare wheel / jack etc. secure in the back? I bet it's something stupid like that!

Neil

[tim_s]

i wish mate! had the exhaust adjusted and checked when up on ramps, it was fine anyway and made no difference when they finished with it anyway. have also removed literally all trim from the back of the car, spare wheel and jack included
i know what you mean though, i'm 50/50 between it being something stupid like that or actually being a bush gone...

[stuartgallafant]

i had that on my iS and it was the exhaust hitting the spare wheel well!

however, try looking at your rear subframe bushes, trailing/link arm bushes, and even the rear turrets where the top of the springs meet the chassis

[E30BeemerLad]

aftermarket speakers in the parcel shelf? are the magnets too near the metal and can the speakers jump when going over speed humps.

I have exactly the same noise, but have been too lazy to ever investigate. Strut top mount would have been one of my first points to check though.

[fuzzy]

i had a knocking that i couldnt track down from the back.eventually found it to be the prop shaft centre bearing, the knocking was prop hitting the tunnel in the floor.man at ecp told me that they are prone to breaking.

[tim_s]

lol, some good suggestions fellas, still not sure any of them are it though

exhaust is definitely clear, replaced the prop centre bearing this yr, only 4" speakers in the rear deck, no horrible cut-out parcel shelf for me. thought that was a well good possibility, am gonna check the rear spkrs just in case! but they've been in there years and no trouble before. i'm not sure about subframe and trailing arm bushes, gonna get another guy i know to have a proper attack of them for any movement, reckon the garage i asked to check them didn't check enough, a visible inspection is not enough.
was too busy playing with my throttle bodies and my mate's s2 to have a look at it today, will have to have another proper go at it sometime.

[MONSPORT42]

Know it sounds stupid but check your boot's closing properly and the lock adjustmentt's OK!!