Rattling noise from top end (4.8is) - help appreciated :-)

[Lion Heart]

Hi guys

Trying to diagnose a couple of issues with my new 4.8is.

There is a rattling noise from the engine. Definitely sounds like it's coming from the top end. More noticeable on the nearside, but seems to be both sides.

You can also hear the noise well from the front wheel arches as well.

I've taken two video's to show the issue (24 and 43 seconds so kept it short and sharp!) Can you guys take a look and let me know what you think:

VIDEO 1 (inside engine bay):
[url=http://"https://www.dropbox.com/s/ebeiblvuf2...N2718.AVI?dl=0"]https://www.dropbox.com/s/ebeiblvuf2...N2718.AVI?dl=0[/url]

VIDEO 2 (outside car and wheel arches):
[url=http://"https://www.dropbox.com/s/5pxhkj9nb7...N2719.AVI?dl=0"]https://www.dropbox.com/s/5pxhkj9nb7...N2719.AVI?dl=0[/url]

What do you think is the likely culprit here?

Thanks guys!

[X5Sport]

Timing chain guides are well known.  If worn then they need doing urgently as a fail can destroy the engine.  They are plastic and just drop into the sump!

[Lion Heart]

Interesting! Is that a big job?

Are these the same chains you can see when you open the oil filler cap (i.e. around the cam)?

What about the vanos on the end of the cams? I've been doing some Google research and they are saying it's common for those to rattle, and they make repair kits for those also.

What do you think?

[X5Sport]

Could be the VANOS as well.  A couple of folks have done either or both.

I think you need special tools too.

Another reference site would be Xoutpost in the US where they have more V8s......

[Greydog]

For some reason I can't access the drop box files however even for a competent mechanic the chain guides and Vanos repair is a huge job and need special tools.
Having had an engine failure and rebuild as a result of chain guide failure I had a good opportunity to examine the internals also the guy who rebuilt it is a Porsche/BMW engine man. He has worked on many BMW V8's and said first sign of chain guide issues is a rattle at cold start until oil pressure builds, the Vanos will start to rattle if the seals are worn when the oil is up to temp and thinner. You can also get sticking Vanos solenoids which may give some noise. If it is seals Vanos noise will lessen as revs rise and oil pressure increases he told me a heavier oil 10w 40 had been used by some garages even BMW to quieten noisy Vanos

Fingers crossed for you

[IanP]

Dont forget that the 4.8 engine is more complex than the 4.6, it has a set of levers on the inlet side between the cam and valve (variable lift??) which can give problems. Look on XOutpost as there are threads on there about this.

[Lion Heart]

Hey greydog and ianp, both good points!

As for te rattle on start up I would say no. I will check this again later, but from memory no rattle on cold start, and all seems ok at first until the revs drop (settle down to normal idle spped as idles at higher revs when you first start it of course). I have experienced exactly what you describe with worn chain followers and cold start due to no initial oil pressure in Audi's and this seems different - certainly upon start up anyway.

What are these levers called or referred to as ianp,mwill look into that also...

[IanP]

Real OEM calls them intermediate levers so I seem to remember the yanks using the same term