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Anyone know what this is?

Discussion in 'A4/A4 cabriolet/S4 forum(B6 chassis)' started by Mikebabs1, Jul 24, 2007.

  1. Mikebabs1
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    Mikebabs1 Member

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    Hi all,

    I noticed a strange noise in the car a while ago now which has gradually got louder over time, to a point now where I struggle to hear the radio. It's very difficult to describe, but it's a sort of reverberating sound which seems to engulf the whole car, as opposed to coming from any 1 particular area.

    It's only really noticeable when cruising at a constant speed, and at around 3000rpm in any gear, and at its loudest at over 75mph in 5th. If i drop below 75 it's hardly noticeable, but over 80 and you need to turn the radio up to hear the music! At under 40mph it sounds perfectly normal.

    It's not bothered me until now as I've had it regularly serviced and there didn't appear to be any other symptoms, so figured it was just the age of the car making it a little more clunky.

    However now that it's got noticeably louder all of a sudden, I figured I needed to get it looked at. But before booking it into the garage I took a look under the bonnet and noticed that a braided tube in the top middle area of the engine bay has become detached. I don't know if this is the cause of the noise problem, or just coincidence. See photos below showing the detached tube ...

    Engine bay showing area where fault is: http://www.flickr.com/photos/mikebabs1/889359914

    Close up of detached tube: http://www.flickr.com/photos/mikebabs1/889385726

    Does anyone know what this tube is and/or the cause of the noise problem I've tried to describe?

    Incidentally the car (as per signature) is a 2001 2.0 petrol with 77k on the clock and is yet to have the cam belt done, which I'm also planning on having done in the next week or 2. I initially thought the noise could be the cam belt, but now I'm not sure.

    Thanks all in advance.

    Mike
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  2. 46TheDoctor
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    46TheDoctor Valentino Rossi A.K.A The Doctor

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    :) Why dont you re-connect the pipe and see what happens? It clearly shouldnt be disconnected., looks like the vacuum pipe onto your master cylinder which will make a bit of a noise if detached. Bet your brakes go better when you refit it too.
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  3. Mikebabs1
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    Mikebabs1 Member

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    Thanks for the info. I've tried to refit it obviously, but the pipe has actually split just above where it connects, so there's half an inch or so of the braided pipe still attached to the connector, making the remaining pipe too short to re-attach. Going to try to get it looked at today.

    Cheers.

    Mike
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  4. Mikebabs1
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    Mikebabs1 Member

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    Took it into my local Audi specialist at lunch and you were right about it being the vacuum pipe. He fitted a new pipe for me there and then (with no charge), and it seems to be better but I won't know for sure until I drive home and get up to a decent speed.

    Thanks for your input.

    Mike
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  5. Mikebabs1
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    Mikebabs1 Member

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    Unfortunately it seems that this wasn't the cause of the noise problem, as it is still happening.

    Anyone have any ideas what could be causing it? I've also noticed a hissing sound coming from the bonnet when I get out the car after driving it. Lasts a few seconds then stops, like there's some air/gas escaping from somewhere.

    It's booked back into the garage on Monday to have the cam belt and everything done, so hoping that might sort it out, or if not hopefully they'll find out the cause.

    Cheers

    Mike
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  6. doogleman
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    doogleman Member

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    I have this hissing noise from my a4 when i get out of it also, i think it is common enough and might be to do with the climate control. No doubt I'll be corrected if im wrong, but Im sure its nothing to worry about. Im not anyway!!! :thumbsup:
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