Help Please Intermittent rattle when idling - video - any ideas?

Gregsy

Gregsy
Hi all.

My 2010 B8 S4 has started making an intermittent (every few seconds) rattling noise from the engine when idling. It sounds like a bearing or loose shaft noise, the video better shows what I mean.

I've recently done quite a bit of work on the car and not many miles since so hoping I've not left something loose.

I walnut shell cleaned the intake valves and intake flaps as I was getting the "P2006/7 intake runners stuck" fault code. Supercharger oil changed and charge coolers pulled and cleaned. Engine oil changed to 5W-40 as I was topping up frequently. Spark plugs changed and gapped. The car's done 116k miles. It's running a lot smoother now and no more engine warning light since cleaning and freeing off the intake flaps.

Can anyone easily identify the likely cause of this noise:


Cheers
 

Audiforlife

Registered User
Sounds exactly like mine did a few weeks ago. Although mine is a 2.0 tdi. It was the alternator pulley had seized causing the auxiliary belt tensioner to dance around

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Gregsy

Gregsy
Cheers, I'll have a look at that.

Did you need to change the tensioner or the alternator?

My battery is very low and needs renewed so maybe the alternator load is causing issues. I've been putting off changing the battery as I've no way to code the new one in.
 

Audiforlife

Registered User
The alternator pulley was the culprit. So I changed that along with the tensioner and the belt while I was at it for piece of mind.

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Gregsy

Gregsy
Doesn't the car need to know a new battery is fitted so it charges at the correct rate and power management is adjusted for the new battery capacity? If the system has adapted to depleting capacity the new battery won't be fully charged. That's my understanding of why coding is needed. If I'm wrong then I could change the battery while I'm at the alternator/noise issue.
 

Simon

Registered User
I had a rattle on mine at idle that turned out to be the flex plate bolts!
 

Gregsy

Gregsy
On the clutch? I hope it's not that. The noise is coming from the front, I'm going to have a poke about in the next couple of days when I get a chance.
 

Simon

Registered User
Thinking about it bottom pulleys are known to fail on these, worth checking out
 
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