BMW 720d

[ratour]

I can hear a knocking noise at low speeds coming from the back. Only when I go over bumps or potholes. Otherwise the car drives fine. Any ideas what it could be? More to the point how much is it likely to cost. Year is 2012 F01 model.

 

[Dazza88]

That’s a really open ended question mate, could be so many different things. Have you had a look underneath to see if anything’s worked it’s way loose?

 

[rs500nutter]

Yeah not much to go on im afraid and theres a lot of things that can make a noise on rear of car
Shockers
Anti roll bar
Anti roll bar link arms
Rear trailing arm bushes
Rear exhaust rubber hanger snapped and exhaust banging on underside of car.
If you aint got the means to jack the car up safely to have a look im afraid its a guessing game at the min otherwise take it to a local independant garage and explain the noise and the area its coming from to be on the safe side ok

 

[ratour]

Thanks for the replies. I have had a look underneath. Exhaust seems fine doesn't look like anything is loose. It doesn't make the noise on the motorway at higher speeds. Only does it on low speed under 30mph. It's quite quiet you can't hear it above the radio. The noise sounds like a metal on metal bump. It's actually louder outside then in the car.

 

[rs500nutter]

Last time someone had a noise like that i sorted was the boot latch had come loose and was banging over slight bumps in the road etc.
Could also be rear shocker top mounts aswell.
Ive even had a car in with a rattling noise in boot area and it was the wheel wrench that had come loose that was supposed to be fastened in with a bolt that held the floor jack in place aswell.
Also lift out the rear boot liner and check something aint loose rolling around etc.

 

[Dazza88]

Been a slight knocking on mine, went in for service today and rear right coil spring completely snapped on it.