S8 owners: howling noise at ~900 rpm with warm engine and cold air?
03-15-2007, 02:47 AM
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S8 owners: howling noise at ~900 rpm with warm engine and cold air?
I'm having a bit of an issue with a sporadic noise, located somewhere in the engine bay, and the problem is replicating it on demand for the A8 tech to diagnose.
The issue occurs mainly when the ambient air is cold (50F or under) and the engine is hot, for example after a flowing 70 mph run for 20 to 30 miles or more. The noise is a kind of harmonic or resonating howl/whine which is noticable at around 900 rpm, whihc means in practice it's audible when travelling slowly along residential streets near my home. The greater the differenc between ambient air and engine temperature, the greater the noise. It got so lound one night during winter when I got home late that it woke my wife up as I pulled into the drive.
I did get the noise this morning after a run to work, and as the dealer is just down the road, I rang in and asked if a tech could come straight out. By the time I'd parked, gone in, waited ot be seen, waited for paperwork and then waited for a tech, it had cooled down and stopped doing it. I did take the tech out for a quick warmup run and he heard a very faint version of it, but that just made me feel l8ike he might think I was complaining about something really insignificant.
He did suggest it might be a resonance in the inlet manifold, and wasn't sure if it was just a design 'feature' or a fault on my particular car. They don't have another S8 in to test aginst.
Anyone else noticed this issue?
The issue occurs mainly when the ambient air is cold (50F or under) and the engine is hot, for example after a flowing 70 mph run for 20 to 30 miles or more. The noise is a kind of harmonic or resonating howl/whine which is noticable at around 900 rpm, whihc means in practice it's audible when travelling slowly along residential streets near my home. The greater the differenc between ambient air and engine temperature, the greater the noise. It got so lound one night during winter when I got home late that it woke my wife up as I pulled into the drive.
I did get the noise this morning after a run to work, and as the dealer is just down the road, I rang in and asked if a tech could come straight out. By the time I'd parked, gone in, waited ot be seen, waited for paperwork and then waited for a tech, it had cooled down and stopped doing it. I did take the tech out for a quick warmup run and he heard a very faint version of it, but that just made me feel l8ike he might think I was complaining about something really insignificant.
He did suggest it might be a resonance in the inlet manifold, and wasn't sure if it was just a design 'feature' or a fault on my particular car. They don't have another S8 in to test aginst.
Anyone else noticed this issue?
03-15-2007, 05:15 AM
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Re: S8 owners: howling noise at ~900 rpm with warm engine and cold air?
Haven't heard anything like that to date but I'll listen for it. Windows are usually closed (it's cold here in Wisconsin) and dual pane glass would muffle a lot of noises I would think. I still get a "shudder" and rough idle for about 30 seconds on a cold start....do you ? McBucky
03-15-2007, 07:43 AM
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Nothing like that as yet. I do a 45 minute 80mph run daily and nothing. The ..
car is as quiet as can be.
For McB, yes, I think all the S8's have a rough idle for the first few minutes. Another post explains that there is a recirc fan that draws exhaust gasses back to the inlet until the cats warm up
For McB, yes, I think all the S8's have a rough idle for the first few minutes. Another post explains that there is a recirc fan that draws exhaust gasses back to the inlet until the cats warm up
03-16-2007, 01:39 AM
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The howling is audible from inside the car, over the stereo on a bad day.
Yes, I do get a bit of rough starting; sometimes takes more than a few seconds of turning over to start, and sometimes runs a little bit 'clattery' for ~30 secs before smoothing down.
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03-16-2007, 01:43 AM
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Update: After firing of a tech query to Audi, there is a pending engine controller update coming out
They're going to get authorisation to run the update today, so I'll drop the car off and get it updated.
We're due a cold snap again on Sunday/Monday next week, so it will be a good time to test it out!
We're due a cold snap again on Sunday/Monday next week, so it will be a good time to test it out!
03-16-2007, 03:05 PM
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Sigh. Update not done.
They had problems getting the update to install, so they've queried it with Audi and I got my car back.
I did find something interesting though; the noise can be made on demand at 900 rpm with the steering at full left lock. Power steering pump?
I did find something interesting though; the noise can be made on demand at 900 rpm with the steering at full left lock. Power steering pump?
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