Slotted grills.
I assume you mean the thing which is about an inch wide by three inches long directly behind the seat bealts.
I also think they might form part of the roof drain.
I did once chuck my coat over in to the hood stowage area (hood was up) and found it made a subtle difference, hence the reason I insulated under there.
Yes, they’re the ones you describe. It’s as if the wind’s blowing out of them from somewhere other than the two drain holes under the car. Sounds like wind blowing down a chimney.
I assume you’ve checked that the flaps are in tact ?
When you have the cover out to do the foam, it might be worth taking a look at the flaps.
These are located directly behind the seat belt reel inside a recess. two or three bolts is all it takes to get to them.
They are just a push fit in the body.
my mk 3 ,was so noisy I was going to sell it ! in desperation I had full soundproofing kit fitted ,the car now is 70% quieter and joy to drive ,an expensive option but one worth doing .
I didn’t know there were any flaps other than the ones inside the drain exits under the car. I’m reluctant to remove the plastic covers from behind the seats, is it possible to
access them without doing this ?
Stuffing socks into and over every visible drain orifice didn’t work so, thinking wind could be entering through the concealed drainage slits at the front of the hood behind the windows, I stuck 6 inch lengths of 1/4 inch self adhesive foam to the inside of the rail above the rubber lip seal…that didn’t quieten it down either .
PS, - It’s a 2006 Mk3 2.0i
I’m really hoping you get to the bottom of this. I have the exact same sound coming from the rear of my 2006 1.8i, again sounds like milk bottle whistle just over my left shoulder, and it is driving me insane.
The flaps I was talking about are the ones that protrude from under the car.
They exit the car directly behind the seat belt inertia reels, so no you can’t get to them without removing the rear cover.
One thing I’ve noticed on mine, which may or may not be related.
The very first inch of the hood, directly behind the seats on the door shut, has an occasional crease in it, which can allow it to fold back on it’s self when putting the hood up.
Drop the hood, look directly behind the seatbelt, just beside the grill we mentioned.
The hood terminates in a V shaped pattern, it’s that V shape which can fold back on me when I put the hood up.
It’s feasible that wind noise could enter here ???
I’ve tried a multitude of things to stiffen that corner, included watered down PVA, to no avail.
Those were the first things I checked after cleaning the drains with a trombone brush. The drivers side was fully closed, the passenger side not quite so until I poured soapy water down and gave it another rodding with the brush. No good, the noise was still there.
Thus far, in addition to the above I’ve
1/ Soundproofed the boot floor, bulkhead. and the rattly plate shielding some electrical connectors on the left hand side behind the plastic trim. Result = a more refined less “tinny” sound from the back end. No change to the offending noise.
2/ Stuck insulation tape between the passenger window and the front edge of the hood which protrudes 1/2 an inch. Result - Nil.
3/ Dropped the passenger window 1/2 and inch. Result = Nil
4/ Stuck foam strips inside the front edge of the perimeter rail directly over the 4 inch drainage slits in the canvas hood. Result = Nil
5/ Laid a folded rubber backed picnic blanket along the bottom of the plastic hood well behind the seats. Result - SLIGHT improvement
Just been for a short drive with the above mentioned blanket and also stuffed small cushions into the wells on the passenger side. There’s a definite improvement and the sound shifted to the driver’s side so I stuffed a cushion in there as well. I can still hear the noise but at less than half the volume.
Upon return, I sat in the car with the engine running and could still hear the noise, VERY faintly. Now I’m thinking fuel pump ?
UPDATE - Tore out the plastic panelling behind the seats and noticed the following - There are two 1 inch thick pieces of underlay with some 1 inch holes in them loosely dangling under the hood well. The only means of attachment appears to be some plastic protrusions moulded into the well, each with a notch at the end, presumably to accommodate a clip holding perhaps a disc or similar device in place. I couldn’t find anything which might have fallen off , perhaps they were missed on assembly. Other than that, there’s precious little sound deadening back there, only a bitumen pad on the driver’s side and two thin squares of underlay glued the the lower part of panel behind the seats.
The fuel pump is covered with a black metal cover held in place by 3 screws. I removed the cover, stuck one end of a 2 ft length of garden hose in my ear with the other end touching the the fuel pump and started the engine. The noise was remarkably similar to the one heard whilst on the move. I can only conclude that the noise of the pump is amplified by the surrounding panels, exiting through various gaps around the upper sides of the seats giving the illusion of wind noise from the hood. The car’s still in bits ready to receive a substantial layer of sound deadening tomorrow.
I WILL conquer this damned noise if it’s the last thing I ever do !!!
Now you mention the 1 inch thick underlay, I do recall applying spray adhesive and sticking mine back in place.
Then on the floor directly underneath the hood tray I laid a layer of 10mm underlay, pushed it as far back as I could, again glued down with spray adhesive, this the came back around (towards the front) where I stuck it the tray hood.
I also glued a bit to the cubby holes.
Like i say, it’s not perfect but is a heck of a lot better.
After spending most of yesterday soundproofing beneath the hood well and behind the seat panel I’m rather disappointed that the windy noise is still there. I can’t say it was a complete waste of time as it’s reduced road and other noises 25% more than soundproofing the boot last week.
The best result was achieved by stuffing a small cushion into each drain well and tucking T shirts into and around the hood hoops and cavities behind the doors. I don’t know which of the two had the biggest effect but I’m sure I’m in the right area and will concentrate more on these over the weekend.
UPDATE 19/5/16.
I’ve finally discovered the source of the annoying noise…it’s the near side rear brake disc !!! The disc looked in poor shape when I bought the car 6 weeks ago so I bought a new set of Mintex discs & pads to fit when in the mood. The other 3 discs are serviceable but I prefer to replace them as a complete set, paint the callipers, de-rust the suspension & inner wheel arches all at the same time.
The outer side was scored and rusty with a clean (ish) 1 inch wide rubbed strip around the centre. After removal I was horrified to find the inside with only a 1/4 inch being rubbed with the remainder in a terrible state. I’m amazed how the car passed the MoT brake balance test.
Anyhow, took the car for a spin with the hood up and low and behold…the so called “wind noise” is completely absent. Obviously the pads had been rubbing the disc and transmitting noise into the cabin.
So, if you have the same noise, check both sides of the discs and make sure the pads aren’t sticking before spending time and money on sound deadening.
Now a very happy bunny 
It just goes to show that things are not always what they seem.
This is so true. The fact that the noise didn’t come on until 20 + mph and sounded exactly like the wind threw me off the scent.