I have had a light knock form the rear of the beast ever since I bought it. It is pretty light, and doesn't seem to happen in time with the suspension. I have checked underneath (anti roll bar brackets OK etc.), inside the boot and the rear deck and I can't find the source.
Did you check ALL the nooks and crannies in the boot? Maybe there's something that's loose or floating around, like a Maglite torch in the space under the M-Mobility kit... I would have guessed possibly your sway bar came loose, but you said you checked that. Then there's the driveline components...
__________________
Mark
2002 E39 Lemans Blue M5
Black interior, Rear fog lights, hardwired V1
Rear sway bar bracket could be broken. Climb under they and take a look. Grab the sway bar and pull it from the ends near the wheel. Should not move much.
__________________ 2001 Dinan S1 M5, Lemans Blue, Blue/Black, sunshades, pdc, alcantara headliner, M Audio) -Dinan S1 (Stage III Suspension, Exhaust, Cold Air Intake, Floor Mats) -Powerchip Gold 91 Software -Stoptech 355mm Front BBK Kit with M5 Logo on caliper -Autosolutions Ratio 2 Short Shift Kit -TC Designs Rear Sway Bar Brackets -BBS CH Wheels, 8.5x19 front, 10.0x19 rear -Michelin PS2's 245/35/19 front, 275/30/19 rear -UF Motorsports IATS Kit -Stage II 62 HID Lowbeams -4300k HID Foglights -Eurospec Center Console w/ Storage -StealthOne -Lidatek LE-30 Laser Jammer -Mark IV DVD System -Euro Angel Headlights w/ Clear Corners -Silvervision turn signal bulbs on all 4 corners -M5 Trunk Mat -M-technic kit with custom painted splitter in M colors -Brake duct kit -35% Madica Film Tint -MB Quart speakers w/ Neo Tweeters/ Monster 1 Farad Capacitor -3M Clear Bra custom install
Is it a low metallic knock or a higher plastic knock? If it's the latter and if you have a powered rear sunshade, it could be that. Try driving around with the sunshade up, see if you still hear it.
__________________
2001 LeMans Blue E39 M5, still completely stock! (except VW MAFs)
2002 318i cabrio, almost as blue as the M (my wife's car)
I had a similar thing with my 2001, which had an occasional knock from what sounded like the rear left.
This only resolved itself when I started getting a vibration from the exhaust when it was stone cold in the morning. This would buzz and resonate at about 2000 rpm then go away literally after about 1 minute of warming up.
Eventually it didn't go away, but sounded like a loose baffle.
Anyhoo, I traced it to the centre exhaust support. The rubber mountings had sagged just enough for the exhaust to touch the metal support under the exhaust.
I changed the mountings for new ones (doable from under the car without removing the exhaust, but a bit fiddly as the top nuts are tricky to get to).
The new mountings had obviously been redesigned as there is far more rubber in them.
Result - all noises, including the occasional knock, gone!
(my wife's car)
Linear Mode
