Help needed with mystery noise

[alpina]

I need some help / ideas regarding a random mystery noise that I have. I have attached a sound file of what the
Noise sounds like. (Note this is not the actual noise, just a recording of type of sound.)

It happens purely at random, and I cannot reproduce the sound when stationary in the garage.
It seems to come from behind the driver (LHD).  I don’t believe it is speed related, however it usually happen above
90KM/H.
It is not a constant sound, it could happen once or twice, and then not happen at all for the rest of the journey.
Most of the trips I take will be around 100 – 150km, over this distance it may happen a few times. On some journeys
I does not happen at all, and I think I have solved the issue, only for it to happen on the next trip.
In the scheme of things it is not a great problem, it is just starting to annoy me now.

So come on chaps listen to the sound and point me in the right direction.
The things I have checked so far: Nothing is lose and moving around in the boot (trunk). Nothing is lose behind the seats.
Brake calipers tight, Brake disk cover plate is tight. Drive shaft centre bearing support tight. Trunk diff mount was replace
2 years ago along with flex plate. Exhaust fittings all tight.

All ideas welcome. Thanks DM.

[Iconic]

The sound file does not play for me.
But, I will go ahead and ask if you have looked into the two compartments with wood covers that are behind the seats?
Good luck !!

[alpina]

Hi Iconic.
yes i have looked there and nothing is a miss. i have now uploaded a zip file the other audio files. when i tried to upload an mp3
i was not allowed to upload this type of file.
thanks DM

[Paul & Dolly]

DM ?
You could upload the sound files to your Google drive, and then just provide a link on here, to those files, so we could play them.

What I did hear sounded like someone tapping a spoon , was that correct ?

Paul

[teahead]

Strange sound for sure.

You looked underneath for anything loose?

[alpina]

yes Paul, that is the sound. it sounds exactly like that. if you cant't hear the sound file, tap your two softtop
handles together and it sounds like that.

[Paul & Dolly]

 is the soft top up or down when you hear the noise ?

Paul

[alpina]

The soft top is always down when i drive

[waltklatt]

DM,
Well I could help, if you could add more information to the kind of sound.
I'm deaf and cannot hear a sound, but if you describe it, I can help.
Metallic clicking, tapping, rubbing, squealing?
Not sure, many things could lead to noise.
Temperature(hot or cold), bumps, highway or city streets?
More information...
Walter

[alpina]

Walter,
it is difficult, its a metalic sound sort of a tinging. it tends to be at higher speeds 90kph or above
but then i have heard it below that speed.  it is not a contant noise, it may happen once and then nothing
or could happen a few times. it was as if someone was sat behind me randomly playing the triangle. https://www.youtube.com/watch?v=jb-UVKB52RY
softop is down. wheather is around 75 - 80F sunny.  Driving over bumps, does produce the noise, it is
generally on straight smooth roads.

DM

[Garry]

It could be the lock down fitting on the soft top or in the case of an early 230/250’s the fixed handles just touching the underside of the soft top Hatch acting like a tuning fork and if you  have your roof down constantly and it has compressed down into the soft top box gives then space to rattle around.

[Jordan]

Sounds like a piece of aluminum or steel hitting glass.  Like what you would hear when someone taps their wine glass to propose a toast at a wedding.

[Paul & Dolly]

Seat belt buckle hitting metal part of seat possibly?

Paul

[Pawel66]

Nothing immediately comes to my mind, sorry, but as I am, sort of a "rattle freak" I do chase all of the noises in the car to get rid of them. I understand how irritating it can be. So some observations:
1. it is sometime difficult to determine the direction where the noise is coming from in the car. The source may be in a different place vs. where you think you can hear it.
2. Exhaust - will behave different hot and cold. It expands quite considerably when hot and it changes the tensions in its suspension. May need to determine if the sound is there cold or hot. If when hot only, go to the tail pipes and kick them a bit or put a glove on and shake them a bit...
3. Does it depend on side windows being up or down?
4. Have you checked if any washer gets lose in suspension when someone is sitting in the car? E.g. the two plates on top of the shock absorbers that have rubber between them? Are they fitted "edge up" so that they do not touch each other?
5. Have you checked the hand brake lines and main brake lines, again, when someone is sitting in the car?
6. Any lose parts of the chair? Any broken spring hanging under the cushion (had it once in W463)?
7. Are all the door chromes tight?
8. Are the door locks tight? No lose washers there?
9. No lose washers/springs/levers in the soft top hinge and soft top cover lock?

And so on and so forth. People here were finding lose washers on drive shaft making random noise... So unless someone can really direct you, it may be quite a lot of systematic checks...

My rattle/noise finds: lose washer in the rear soft top frame, lose screw holding the soft top cover moulding, exhaust - several times, lose nut on the rear hanger, lose harness bracket under dash, window cranks, etc.

[cfm65@me.com]

I have found a loose rivet inside the soft top frame.
Since you always drive with the top down, I suggest you drive with the top up a few times, which would hopefully confirm the noise is inside the car or not.
Regards
Chris

[waltklatt]

DM,
That's a bit clearer now.
Ok, couple of things in addition to what others have said.
How about the tension rods for the top cover and trunk?
Trunk frame pad between the sheet metal and frame?
Heat shields for the muffler?
Parking brake or brake cable(tab broken off), or something.
Will add few more when they pop up in my mind.
Let us know..
Or you can use earplugs. 
Walter

[alpina]

Thanks for all the suggestions.  Off to the garage now, to continue the search. I wouldn't mind if it happened all the time,
that would be easier to track down. Other than this i have no rattles, squeaks, clunks or other strange noises.
These things are sent to try us.

DM

[teahead]

Ya, jack the car up (all four wheels) and put it in drive and see if it repro's while in the air.

Of course be SURE it doesn't move!

May need a helper to help identify the noise.

If no noise, then most likely suspension or body undulations causing the pinging.

[mdsalemi]

I had a similar sound; it was caused by the bottom of the window lifter/glass assembly hitting the bottom of the door.
Took me a while to figure out it only happened when driving with the driver's window all the way down, and that the problem ceased with I rolled the window up even a bit.

I could adjust the stop point, I think something else went wrong.

Simple fix, I took a piece of self stick craft foam (the kind that comes in sheets) and placed some as a cushion right where the part was hitting. Problem solved.

[alpina]

Okay quick update, after carrying out further checks this afternoon I discovered a loose washer in the
Soft top frame. It is on the left hand side, and behind me, so this maybe the source.

I am not celebrating just yet as I have not yet had chance to drive it. Hopefully will go for a drive later in week to see.
I am encouraged though, as it is in a location where the sound seemed to be coming. Fingers crossed.

[Tyler S]

Before you tighten up the bolt, flick the washer with a stick or something non metallic and see if you can duplicate the noise.

[alpina]

Hi Tyler, i did do that, and did give a similar metallic ting. Bolt now tightened to lets see what happens next.

DM

[alpina]

Nope. it is still there   it seems to happen around 100 - 110kph. roof down. one clink / ting and then nothing.
As suggested, i stopped and put the roof up to see what happens. Drove back down the motorway at 100 - 140kph
and nothing. So from that i can assume that it only occurs when the roof is down.
This is really frustrating. so back to the drawing board. Help!