Groningen

Yesterday I posted this:

"When I start my Audi A4 Avant V6 2.4 Quattro (1-99) and drive around for some ten minutes, something, somewhere in the front of the car starts to rattle. But only when I give some gas. In idle mode there's no rattle whatsoever. Just when I'm giving gas. It's not very loud, but loud enough to be heard. The sound appears to be coming from deep within the air system, at least when I put my ear to the centre grill the sound is more pronounced.

The rattle can only be heard when inside the car with all windows closed. Outside the sound is not noticable. Therefore I doubt whether it is the heat shielding of the exaust. I guess I've to rule out the little fan near the Climate control. That thing doesn't make a sound. It's also not related to the climate control. The rattle is also there when the climate control is on.

The type of sound of the rattle lies somewhere between a boiling sound and a ticking sound.

Anyone could give me an idea what this could be? I'm very pessimistic about asking my Audi garage overhere in the Netherlands about the problem. Even this close to Germany they manage to not do their work properly and ask loads of money for not finding solutions to some prblem I had with the car recently. And more important, they did not even know the existence of audiworld.com! Duh! ;-)"

After some tips from forum readers I decided to unplug the radio to hear if the sound was coming from behind the radio (e.g. the little fan overthere. It was not coming from that small vent, nor it was coming from the climate control (I turned that off). But this is what I found out:

The sound is definitive coming from within the airvent system and the rattle is rpm related. The more rpm the faster the rattle goes. The sound of the rattle is like a cassette tape that is beeing fast forwarded (not the sound on the tape but the plastic sound from the spining cassette itself). It seems like it's a ventilator that is rpm related??? Because there are all kind of openings in the vent system everywere in the dashboard, it's difficult to pinpoint where the rattle exactly is coming from. In each case it's hearable from every airvent opening in the dashboard.

Anybody got any idea???

Oliver

BSCA4

the Forge BPV. I start hear the rattle right after. I though my Forge BPV vibrate against the fan motor (since it was big, twice the size of the Bosch BPV).

Groningen

Thanks for your reaction. But uh...could you explain to a simple dutch person who speaks and writes not so good english what a BPV is??

Oliver

Clout

don't worry about it, you don't have one....it's only on turbo cars

Kris Hansen

On my car, I get a nasty rattle right between 2000 and 2500 rpm, really annoying.. It's the rear muffler, though for the longest time, I would have sworn that it was coming from the front of the car.

Can you reproduce the rattle while sitting still? In my case, I could NOT get it to rattle, unless I floored the throttle pedal.. That got the muffler to rattle, which is how I determined that it was indeed from the muffler. With the door open, it was very obvious that the niose was coming from the rear of the car...

Hope this helps!

Clout

beat ya by 59 secs....granted you proved much more info

Kris Hansen

Woah, it took me 59 seconds to type all that?? Man, I gotta speed up!! =)

Groningen

The rattle cannot be produced when I don't touch the gas pedal. It only occurs above 1500 rpm and up and is not noticable outside the car. I had a friend but some rpm on while I was in front, under and at the back of the car. No rattle noticable at all. It seems like there is some rpm related something inside the ventsystem (maybe a fan?). What I found must obscure is that the rattle only appears after the car has run for about five minutes. To me that means that it has something to do with engine heat. I'm almost afraid to ask, but could it be something with the valves??
Last month the car was in the Audi garage for a 120K checkup (new timning belt, filters etc.) I can't remember whether the sound was there before it went to the garage or after.

Finally, it also seems to be more loud than a couple of weeks ago. The rattle is just more pronounced than a couple of weeks ago.

Oliver

Clout

remember the exhaust also heats up substantially as the car is driven.

Groningen

the muffer I guess I should hear something rattle.. What's your opinion?

Oliver