rattle noise on engine start

[ChrisR14]

Hi there,
a friend of mine has a 2014 B8 S4 with stronic and the quattro sports differential. There is an unnormal rattle a few seconds after you start the engine.
Here's a soundfile:


Car has pretty low milage of about 10,000 miles. The local dealer changed timing chain tensioners, did an oil change and did a basic setting of the dual clutch transmission.
The noise is still there. The dealer now says it is normal and nothing to worry about, but in my opinion this does not sound "healthy".

What I can say about the noise:
1. It appears on 3-4 out of 10 engine starts
2. It mostly happens on cold engine starts
3. It also sometimes happens with a warm eingine ( >70°C coolant, >50°C oil temperature)
4. If the last run of the engine was <5min and not driving faster than 15mph, there will be no noise on the next start, even if the car stands for 1 week.


Any thoughts where this comes from?

[levigarrett]

Well my initial response was the tensioners.

http://www.audizine.com/forum/showth...rt-V6-3-0-TFSI

I had them replaced on my car a week ago and it no longer makes any odd noise at start-up.

You say that's already been done although is certainly sounds like my car did before the repair. Everyone at my dealership claimed the tensioner "rattle" is perfectly fine unless it's more than 3 seconds or so. I'm really not sure what direction you should go here. Perhaps someone else has a clue but from the video, it don't hear anything that sounds terrible to me.

[ChrisR14]

The noise is at 0:13 in the video. As you can hear the engine is already running and not rattling at all, then after 0.5sec there is this high-pitched "grrrr". It really doesn't sound like on all the timing chain tensioner videos online, where the rattle is there directly from the start.
I would also say it comes more from the lower end of the car but it is really hard to locate.

[MrFunk]

Normal... Mine's done the same since new.

[carlosvjr92]

If it's a rattle right after turning on - definitely the tensioner. There was a TSB for it. Had it done recently...but this doesn't sound like the tensioner, unless the video just isn't that clear

[Thurston]

Sounds like normal VW/Audi engineering so in other words .. who knows.

[def]

I'm in Canada. Same noise. Asked about the tsb. They said there is no tsb for that here.

In the end they called Audi Canada I guess and are replacing the tensioner under warranty.

[S4'ed]

Secondary Air Injection Pump?

[cobrario]

Mine makes the same noise and I never gave it a thought.

[LittleDozer]

I'm in Canada. Same noise. Asked about the tsb. They said there is no tsb for that here.

In the end they called Audi Canada I guess and are replacing the tensioner under warranty.

Did they have to replicate the noise at the dealer? Mine does it occasionally on cold starts but it's not incredibly frequent so I worry they won't cover it unless they keep it for a week.

[crimson773]

Mine makes that noise too and I believe has done it since I've owned the car.

[def]

Did they have to replicate the noise at the dealer? Mine does it occasionally on cold starts but it's not incredibly frequent so I worry they won't cover it unless they keep it for a week.

Yes. I had to leave it over night. They confirmed in the morning.

[tgsweat]

Yep mine has always done this since day one.

[jsh139]

Just wanted to chime in and say that my car does it too. I always just thought it was normal. *shrug*

[Silverbullet S4]

Normal

[miztahsparklez]

mine does it as well.. i thought it was my exhaust, but I can't replicate it otherwise. I can definitely hear a similar noise if I'm driving when the car is somewhat cold. It's buzzing through my exhaust. After the car warms up, it's silent though.

[nickskeeta]

Mine does it as well, sounds normal

[snowmuch]

Same here, had this noise since day one

[miztahsparklez]

Does the noise go away after a fresh oil change?


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[TheAsset]

This....This is what a good rattle sounds like. Mine is going into the dealership tomorrow. 2013 S4 with 25k miles.

https://youtu.be/4JrR04p1rYk

[cjw]

^ that's worse and longer than mine. Mine admit 3-4 rattles, less then a second.

[jsh139]

Yeah, that's a rattle. Mine does what the OP's does. A little short buzz sound. Almost sounds electrical rather than mechanical.

[miztahsparklez]

Bad injector maybe?


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[cW6mT mKviGLi]

For the first 55k miles my car has never made this tensioner, rattling noise. Around 55k it started doing this when first started in the morning, before sitting overnight. Last weekend the car sat from Friday evening through Sunday evening and it rattled for about a whole 5 seconds versus the regular 2 seconds for when sitting overnight.

What happens to a TSB outside of warranty? Is it considered an out of pocket repair? I turned 58k yesterday and of course I'm modded so they might be reluctant to cover anything.