Recently my 86 560SEL started making a rather weird noise.It's coming from the back of the car.It sounds almost exactly like a slipping fan belt,except as I said the noise comes from the back.The car still runs absolutely fine,but as you can guess it is a little worrying.The noise gets worse when I press the accelerator.Anyone have any idea what it is?I was guessing maybe fuel pump problems,or as I have recently converted it to conventional shocks (it had self levelling suspension) maybe some problem with that.However,I had that job done two months ago and haven't had a problem until now.Anyone have any ideas?I would be most grateful for any advice received.Thanks in advance.