It appears in doing so, that I got a 5 taps/second noise from the under dash area in the cubby hole storage at idle. Further investigation eventually lead to the right hand underbody cladding coming off to discover the Fuel Tank Black Vent Pipe was tapping away inside the enclosed metal channel on the front half of the floor pan. Initial padding couldn't prevent it returning and it was quite loud when the air temperature was at 0'C and below.
5 years ago in 2006/2007 there used to be a VAG TPI for this chassis floor pan due to this vibration. The solution was to fit 2 rubber rings. Eventually they altered the fuel pipe lengths to alleviate the problem occurring. Seem to have worked on mine with the change of lengths until I had to move the Low Pressure Fuel pipe in the engine bay.
So I've ended up fitting the TPI (not listed for Scirocco) to remove the vibration generated noise. The reason it taps at 5 taps/second is because once the cold start is past the early 2 minutes of warm-up, the Tank Vent Valve starts to work at idle at 5 openings/closures per second and pulses the Black Vent Pipe. If the engine revs, the valve stays open.
I used 4 Rubber Rings fitted along the Black Vent Pipe as I noticed the pipe could still vibrate with only two in place as VAG recommend.
The positioning in the enclosed channel on the front part of the Floor Pan is very deliberate and the dimensions shown should be adhered to. The 4th Rubber Ring stops a touch point further to the rear.
1) Parts required:
2) Initially remove the two small panels at the front end of the Floor Pan Cladding as these overlap the main Cladding. One had two Torx Bolts. The other is popped into the Chassis Floor Pan hole, see here for removal guidance
Undo the 8 main Cladding captive holding bolts. The Cladding should easily drop away. Try to hold it in the middle while it comes off so it drops off balanced on your hand.
3) Remove the soft foam pad surround at the rear entrance to the enclosed Channel Section.
4) Now for 3 of the Rubber Rings, fit onto the pipe shown and wrap with tape.
5) To aid positioning the Rubber Rings into position as shown in the 3) photo, the tool is quite simple.
6) The 4th Rubber Ring is fitted further back on the pipe outside the rear end of the enclosed Channel.
7) Finally refit everything in reverse, noting the small torque settings. With the Underbody Cladding, it is easiest to hold it balance on one hand and off up, tightening the 2nd row of Underbody Cladding plastic nuts from the front and then fit and tighten the remaining nuts. Followed by the two small panels.
Self inflicted I suppose but there is a get out clause
. Postscript 19Dec2012 :
A lower level sound besides the "tap..Tap.." which I always thought was the engine idling has also now gone. Can't hear the engine now, just the rear muffler box spluttering. So a worthwhile modification considering the cost and ease to do it even if the "tap... tap..." from the Vent Control Valve vibration is not present.
C.
( Fuel line tapping, dash rattle, vibration noise drivers footwell )
