Help me diagnose a clacking sound from rear

[iamsam]

* Update w/ pics, see post #23 *

Background:
1991 318is, H&R Race, Billy Sport, Kosei K1 15x7, IE billet alum RSMs, 210k miles, rear seat removed, rear carpet removed, all trunk carpet and spare tire removed, ski hole plate removed, so I hear everything.

Symptoms:
A loud clacking sound has very recently developed from the right rear when I drive over harsh but small bumps. Sounds like it is coming from in the trunk, not a dull thudding from the subframe or something. Seems to happen when the suspension is jarred, rather than long and smooth suspension travel. I hear the clacking from inside the car w/ the windows up. I can't replicate the clacking at all by jumping up and down in the trunk.

Attempted fixes:
Adjusted the trunk so it shut snug with no play, took off rear right wheel to inspect, bent the brake dust shield back into place. It isn't the RSMs, they are in great shape. I assume the bushings are original, and shot.

Suspected diagnoses:
Could be bad subframe bushings. Do bad bushings make this sound? There may be something loose in the battery tray, but it doesn't really sound like that kind of noise.

Can anyone help?

Thanks guys.

[iamsam]

this sounds like a similar problem: http://www.r3vlimited.com/board/show...frame+bushings

[barry]

Check Differential bearings etc. also half shafts.

[iamsam]

Check Differential bearings etc. also half shafts.

as in tear apart the differential?

[barry]

Jack the car up and move the wheels or start car and run the gears, listen and feel for slack etc. also check calipers for loosness etc. Do you have a loose jack in the trunk banging against metal or loose gas tank or muffler strap.

[iamsam]

there is absolutely nothing in the trunk at all except a battery. You guys don't think it could be bushings?

[barry]

The bushings are easy to check, use a crow bar to check for movement. Half shafts will clack if the big ball bearings are worn, checK and see if the CV boots are ripped.

[iamsam]

Will try the crowbar approach. The CV boots are dry rotted slightly, but not ripped. How can I test for bad CV joints? Keep in mind, this is a clack that I hear clearly from inside the trunk, almost as if something is smacking metal literally in the trunk, and the sound comes into the cabin through the ski hole.

[barry]

Sounds like half shafts to me. Jack car, start motor and you'll no right away. make sure both wheels are off the ground. Rememeber the differential connects right in the middle of trunk. Do you here the noise when turning under speed sharply? Could also be drive shaft joints, most of these things can be hand tested.

[iamsam]

the clanking is bad when I am going over bumps on a hard right turn. how do I test the half shafts? Just run the car in gear w/ the rear wheels jacked up? how will I know right away? I jacked up one wheel and ran the car in first gear (open diff) and there was no noise.

[barry]

Listen find a parking lot and do 360's both left and right If there is no clanking you may have a broken shock. If it only happens going over bumps somthing is loose or broken. Also check differential and Tranny mounts.

[Ryann]

are all your exhaust hangers intact?

[619E30]

Loose muffler?

[E30_fiend]

I think I may have the answer to your problem. Go ahead and check the brake caliper bracket bolts. They are known for backing out at least I have seen it happen a few times. Caliper bracket bolts arent something you usually think to inspect and also they are easily overlooked when inspecting CV boots and the like. Check that then check back.






Taylor

[iamsam]

Listen find a parking lot and do 360's both left and right If there is no clanking you may have a broken shock. If it only happens going over bumps somthing is loose or broken. Also check differential and Tranny mounts.

I'll have to try this. I know the diff bushing is on its way out, and i'll have to check all the bolts to see if any have backed out.

are all your exhaust hangers intact?

Loose muffler?

I don't think so, I installed a new muffler about a year ago, but I will check

I think I may have the answer to your problem. Go ahead and check the brake caliper bracket bolts. They are known for backing out at least I have seen it happen a few times. Caliper bracket bolts arent something you usually think to inspect and also they are easily overlooked when inspecting CV boots and the like. Check that then check back.

My right rear brakes are wearing the rotor funny, has been doing it since I bought the car, the brakes seem only to be contacting half the rotor....