Clunks and whines

[flyingguy]

Hi all, first post here. Just bought a 2011 van, 79k and one owner. It's in great condition overall but has a couple of annoyances. When driving there is a sort of knocking sound from the rear, it's not consistent and can happen when cornering or on a straight road. It doesn't happen specifically when going over bumps etc. Took it back to the seller who has been fantastic and he took it to his mechanic and they spent hours underneath and couldn't find anything obvious to cause it.

Also, very intermittently I can hear a high pitch whining noise from the rear too, sounds a bit like something is grinding etc, but as I said it happens sporadically. I'm thinking of taking it in to another garage for a second opinion but just wondered if there is anything that may need replacing given the age? It doesn't look to have had a hard life, interior is immaculate, looks as though it was used for very light work. Full service history too. 

Any suggestions appreciated. Many thanks!

[Sol]

Could be the rear shock mount or spring perch knocking, or even the spare wheel cage knocking, have you checked it's tight, the bolt is just inside the rear doors. My van doesn't do it but I had a BMW that did and it turned out to be the spare wheel cage under the back.

Anyway the shocks on the rear mount to a plate, and that in turn bolts to the body. The pin bolts could be worn as there's a metal ferrule in the shock eye at each end, and the top and bottom bolts are different sizes. They could have put 2 same sized bolts in which would clatter maybe.

A mechanic with a lift and pinch bars should be able to find the source. It may not be possible to tell with the suspension under pressure, I'd expect to lift the van so the rear wheels droop, and check it that way.

The whine could be a rear wheel bearing that's worn, it can whine on and off depending on the direction of lateral loading as you drive.