2005 MCS convertible with 70K miles. Rattle happens only at speeds under about 35 mph. I hear it way more than I feel it. Sometimes sounds like right rear – other times middle rear. Has gotten progressively worse over past few years. I’ve got a Hotchkiss 19MM rear sway bar which has been on for years. In the last 3K miles I’ve replaced: Rear sway bar end links, rear sway bar bushings and brackets (H-sport kit), rear struts (Koni FSD), and upper strut mount bushings. None of this made any difference. Control arms and trailing arm bushings are original. Muffler straps are rusty but solid. Muffler hangers are fine. Welded rod hanger (half way down the straight exhaust pipe before mufflers) is not broken. I’ve inspected everything underneath. Cannot figure it out. Could be coming from rear window. Could also be coming rear hatch area (it’s a convertible).

 

Rear seat backs and bottom and rear plastic side wall trim are all out of the car at the moment. Rattle is not related to any of those parts.

 

Could it be the exhaust heat shield?

 

I've taken off the square shaped shield that protects the battery. Was hoping to find a large rock loose on top (nothing). Will look more closely at other heat shields.

 

Can you post a video or audio file of the sound?

 

You can hear it well in the first ten seconds and again from 0:22 to 0:40.

 

Did you by chance use the OEM or similar foam strut top bushings? I had 3 sets fail and this was exactly the sort of rattling I heard until finally going to Powerflex yellows for the top bushes, which stopped it completely. Ruined one of the Konis .

Worth a look, especially if you can get the car up on a lift and push up on the wheel...you'll know real quick if they've gone flat.

Good luck!

 

I had a rattle in my Vert that was driving me crazy. I finally figured out the end link was loose on the rear strut.

I do know that the gas tank can rub on the x braces, I put some rubber strips on the top of the x-braces that I glued on with contact cement.

 

Replaced the original foam upper strut mount bushings about 3K miles ago with OEM replacements. Did not make a difference.

 

Here's another video of the sound. This time with top up.

 

Rear wheel bearing, maybe? Sounds like pinging in the second video, and looks like it makes the rattly noise in the first video when the body shakes.

Jack the rear end up and move the wheel around, if you can shake it around, especially up/down, it's a wheel bearing.

 

Here's what the rear right wheel looks like when jacked up and shaken. I think thats too much movement. Didn't have time yet to watch from underneath. Feels like a bushing must be shot and/or maybe a control arm.

 

Yep, that's a control arm bushing! The wheel would be jiggling around on the vertical axis with a shot wheel bearing. Waymotorworks sells the Powerflex LCAB's for a great price. Best money spent ever, totally transforms how the car drives, and you'll never have to replace it again. While you're at it, check your ball joints too!

 

Just clarifying... My issue is with rear suspension.
Are you talking about #9 "wishbone, lower" in this RealOEM diagram?

 

Whoops, you're totally right!

Hm, yes, I'd think it was the trailing arm bushing. Something back there is definitely very tired. I'm not too experienced with rear suspension troubles on these cars yet, I'm sure someone else will chime in with a better response.

If it is the trailing arm, though, take a look at the Powerflex replacement bushings. Might even be cheaper than replacing the whole arm. Polyurethane bushings make for a very nice driving experience, and good a good polyurethane bushing fails much less frequently than its soft rubber OEM counterpart.

 

I would say upper strut mount in the rear or the trailing bushing.

https://www.northamericanmotoring.co...ts-of-toe.html

 

I had a similar issue the day I picked up my car. Turned out that the previous owner didn't screw in the metal brace that holds the battery in place.

 

Battery is tight

Latest theory is the vapor canister up in the wheel well behind the liner.

 

Another suggestion: Be sure that your rear sway bar is centered. If it's shifted one way or the other, it can make intermittent metal-to-metal contact. Don't check with the car jacked up, only with the suspension loaded.

 

1. Wrapped the vapor canister in foam insulation.
2. Tightened end links.
3. Confirmed that the sway bar is centered.
4. Wrapped (convertible) hatch latch hooks in electrical tape.

No change.

Sounds like a small metal part loose inside a plastic container. New theory is something inside the rear bumper. FWIW PDC system gives steady scream in reverse indicating one or more sensors failed. Maybe PDC harness has come disconnected... But hard to believe it would rattle that loud. Could also believe its coming from rear hatch trim. Or right rear tail light area.

 

Since this hasn't been mentioned, I'll toss my thoughts in. Check the rear calipers for rattling pads. On my R53 the driver's rear caliper spring was worn out so the outer pad was rattling against the caliper. I re-bent the spring some which tightened up things and the rattle was gone. It's been rattle-free for about 500mi. Maybe this will help.

 

Good thought. I will take a look at the springs.

On another note I just took a ride with my wife driving and me in the passenger seat and immediately heard noise coming from the door latch area. I could stop the noise by pulling the door inward. Video shows how loose the door is. When driving it doesn't clunk like in the video, but it does make clicking noises that seem to radiate backward in the side wall behind the door. Time to see what Bentley says about adjusting the door latch.

 

Moving the door latch striker inward by less than a quarter inch solved the door rattle. Blue tape shows original striker position. One rattle down - more to go.

 

Even though the rear rattle cannot be reproduced by shaking the muffler... I'm thinking the muffler may be the source. Looks like the inboard muffler hanger on the right side is shot. #14 in this RealOEM diagram. Pic is below shows muffler being pushed hard to the right. Rubber part looks like it may be separated from hanger frame. Also looks scuffed like its been hitting the frame. Really hard to get a good look at it - even with the wheels off.

 

Tested by riding the brake. Tried both regular and hand brake. Rattle noise was unaffected.