I've noticed for quite a while that when my engine is running at idle, if i stand out front near the hood, the is a rattle along with the idle, almost as if something is loose in the engine.

I was told by the dealer that this is normal, and they compared it to another A8 on the lot.

Has anyone noticed this subtle rattle on theirs?

BTW, the car runs perfectly normal also...

 

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I have something similar.

-Rattles on a cold start for about 5 sec if the car hasn't been driven for a few days, winter or summer.

-Doesn't rattle after running for about 5 sec.

-Doesn't rattle immediately after initial cold start if the car is driven daily.

-Doesn't rattle while being driven.

 

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even then, only if the car's been sitting for a few days.

 

I'll have to take notice if i hear the sound after driving a bit.

I've notice it only when starting the car and before driving it.

Steve

 

Be very wary of the water pumps-they arn't the greatest bearing. If you hear a rattle noise from the timing cover on the front-it could be water pump. Usually worse cold and usually more audible at idle due to other noises are lower. Buy one of those stethescopes and check it yourself.

 

Steve:

My '99 had an exhaust shield rattle when cold, just above the RH cat. Easy to fix by snugging the pal nut fastners.

With noise coming from the very front of your car, I would give a quick check of the cam belt tensioning. Be a $$$ shame if the belt came loose. Heard of this happening on some 6 cyl Audi's; don't know if the A8 is prone. The upper belt covers just take a moment to pop off, then watch and listen from cold start with hood open.

Also check the accessory serpentine belt tensioning.

Hope this helps.

 

I have the exact same issue...although it does it each morning when I start the car. It has been cold (28-45 degrees) when the car starts, when it is warm, there is no sound...the rattle is there though, the sound is awful...have we figured this out yet?

 

Certainly, could be hydraulic lifters leaking down. Would certainly be more noticeable after the car has sat for a few days (or longer)

This is a tapping noise at the valve covers.

Can't do much about it, unless it is just one or two lifters consistently (replace 'em)

Not to be expected in a modern car. Used to be a symptom of a worn engine (low oil pressure; worn lifters)

My old Audi 200 had a lifter tap after sitting in airport parking for a few days - come to think of it.

 

Ok so my 2011 had the same issue I might have an answer for this theres a black cover in the front forget if it's metal or plastic make sure to tighten it up as much as possible and cover the little pipe thing it covers off to the right side with tape or something I uses like a 1 inch wide velcro piece normally used to hold electrical wire together to make it look clean an organized. That will stop that horrible rattle noise and it's weird because the noise is definitely rattling and resonates the engine 🙄.
But yes seems to be a common thing and when yoy do that the car can be heard purring even my diesel 2.0 sounds great without that obnoxious noise lol.

***located in front of car, behind passager headlight just under the plastic engine cover, kind of between radiator fans and passenger light and the motor. (But look to bottom of plastic cover cant miss it)
Only other cover in that area black with a hose or pipe it's covering coming out to the right underneath the cover, kind of a round shape beside pushing out to the right obvious.

*don't believe me find it and just put your hand on it and it will stop and motor (should sound better because its not a motor noise but a plastic or metal shield)

Hopefully that helps someone i know its an old post but if anyone know my 2.0 tdi just started to make a metal smacking noise when started at idle unless it's at 1000 rpm or higher I also think I have an injector going out please help.

 

Old post and a 2011 or a 2.0 TDi is not germane to this forum, but rattles in the front of a D2 engine can be the accessory belt tensioner or the fan support bearing. Either of which will leave you stranded, and the fan dismounting can damage the radiator, hood, etc.
The tensioner roller on the 40v can be replaced with a roller for a Hyundai 2.7 DAYCO Part # 89010 or GATES Part # 38027