Rattling noise under car

[eqwalker]

Well, I have got 1k miles now on my smart and the car has been performing great. On my way to work day before yesterday, I noticed a pretty noticable rattling noise, or should I say a metal pinging sound (almost like a metal washer spinning or vibrating on a loose bolt, although I have no proof of that) from beneath the car. Depending on road conditions, it may rattle continuously, or just occasionally. Last night I got under the car and looked as best I could but could not see or feel anything that was obvious. It appears to be related to the rear wheels. You can hit bumps in the road and it will make the noise when the rear wheels hit the bump, not the front. I noticed this morning that even a big gust of wind will even cause it. When you slow down below 30mph, it will stop. Definitely seems to be vibration caused. The car is still functioning normally and shifting normally. Gear selector works fine. The noise though is definitely noticable inside and distracting. Sounds like something small to me. Anyone had that issue with theirs, or any suggestions?

[lhoboy]

Put the car in neutral and rev the engine to the same speed it would be at 40 miles per hour. That will provide one clue.

Does the presence of the noise depend on the roughness of the road surface? that would provide a second clue. Let us know.

(of course, taking it to the dealer is another option)

[eqwalker]

Putting the car in neutral and rev'ing the engine does not cause the clinging to appear.
Yes, the roughness of the road does have a factor on causing the clinging sound. I have spoke to my service manager and he is checking it out.

[jwight]

100% guess, but something is loose or interfering with the under body somewhere. Loose clamp, cable, bolt, who knows? Please let us know what you find.

Thanks!

[KingNine]

Check to see if the passenger seat belt buckle is rattling against the door pillar. I had that happen and I thought I had something going on in the right rear suspension.

[SmartAzz]

Check if holding the ebrake a bit stops it - I recall someone else finding that a lose emergency brake cable was the source of the rattle on their Smart (and actually i have had this on two other cars as the source of a rattle).

[eqwalker]

That was me that posted that on another post. I had forgot about this actually post that was specifically on it. Yes, it was the emergency brake linkage that was chinging under the car. After I operated the E.B. lever it quit. I have occasionally heard it a couple of more times, but immediately got it to stop by operating the E.B.

[mfoster]

I have that same noise. Enough that I want to go to the dealer and test drive another car to see if they all have this. The rattle sounds like a loose license plate frame rattling against the plate itself at certain rpms. The plate frame is tight so I'll check the EB cable.

[Quagmire]

I'm having the same problem. It seems more noticable under acceleration. Sounds almost like a heat shield rattling. Any one have this issue.

[SeaDoc]

open the engine tray in the back - i found two small license plate screws moving about - noise went away thereafter...