Flapping/buzzing noise from behind dash on LHD Syncro

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cobblers
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Flapping/buzzing noise from behind dash on LHD Syncro

Post by cobblers »

This is driving me absolutely potty!
I have a loud, speed related buzzing noise coming from behind the speedo. Starts at 30mph ish and gets worse.
So obviously, it's the speedo cable? Well I replaced it, and it made things no better. So I rebuilt the speedo. No better.
So I disconnected the speedo cable from the diff entirely, and guess what, No better!

I noticed the other day that it's wind related, and sounds like a tag or bit of plastic flapping in a breeze, but loud enough to be the noisiest sound in an un-sound deadened van with mud tyres on at 55mph. 

I've had the clocks out and looked everywhere, I can see nothing, and I've been elbow deep in the dash feeling around to no avail.
The wiring loom grommets are all good. The heater vent positions have no effect. I've blocked the vent channel/crash bar thing with sponges to rule that out too.
I've had the grill and headlights out, looked behind the radiator too. I can't find anything and I'm absolutely at my wits end!

It's triggered by the wind coming at the front of the van at 35mph or so. I've heard it once when stationary on a mega windy day.

Anyone got any ideas?

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Re: Flapping/buzzing noise from behind dash on LHD Syncro

Post by RogerT »

Airbox? Failing foam rubber within,to be specific… Dash out job tho.
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cobblers
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Re: Flapping/buzzing noise from behind dash on LHD Syncro

Post by cobblers »

I don't think it's heater/airbox related as the noise isnt affected at all by the position of the heater controls or when I turn the fan on/off etc.
Sounds like it's coming from almost behind the quarterlight demister vent

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Re: Flapping/buzzing noise from behind dash on LHD Syncro

Post by Mocki »

So to test , seal the whole grill up , newspaper ( do suchh things still exist ) or cardboard making taped accross the whole grill, go for a drive does it stop or reduce ??
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cobblers
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Re: Flapping/buzzing noise from behind dash on LHD Syncro

Post by cobblers »

Well, I've fixed it.
I couldn't exactly tell you how, but rooting around behind the dash, taking the grill off, headlights out, the drivers door card off, poking at all the wiring looms and stuff must have disturbed whatever it was.

There's nothing worse than accidentally fixing something, because you can never properly relax in the knowledge that it will stay fixed.

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Re: Flapping/buzzing noise from behind dash on LHD Syncro

Post by silverbullet »

A broken grille clip can make it flap and rattle at speed ;)
Peeling bits of duct tape (the factory did tape down the odd thing) can also make a right racket.

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Re: Flapping/buzzing noise from behind dash on LHD Syncro

Post by cobblers »

silverbullet wrote: 09 Feb 2022, 14:15 A broken grille clip can make it flap and rattle at speed ;)
Peeling bits of duct tape (the factory did tape down the odd thing) can also make a right racket.

I noticed a few bits of VW duct tape covering the holes in the air duct where the wires would go into the doors. It seemed quite "stiff" to be making that sort of noise but I peeled it off just in case.

My suspicions are that the noise was the plastic door liner behind the door card, it was absolutely shredded and just all left flailing around the place. There wasn't enough to patch up so I just tore it out (not to self, replace this before the door card starts curling up!)
 

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