RangeK1D

Hello folks, I’m back with another A8 My first A8 was a 2005 A8L, had 206,000kms when I sold it, engine drove excellent. My new A8L is a 2008 4.2FSI. Single owner, 165,000kms on it right now. Ice Silver with Expresso brown.

I bought the car with no apparent issues. I drove the car home and the next day I noticed an odd rattle on startup. The rattle seems to be coming from the back of the engine, I nearly soiled myself upon reading a bit into why rattling noises can originate from the back of the 4.2 FSI engine. The rattle is “intermittent”, so it will occur every other startup, sometimes I can have 3 “test startups” in a row and it’ll have little to no rattling sound. When the A8 is sitting on level ground the chances of a rattling startup increase from what I have seen so far.

I have attached a link to the video I recorded today of my engine, please take a listen and chime in.

Any and all suggestions will be celebrated! Fresh oil change has been done with a LiquiMolly engine flush as of yesterday with little to no improvement in the rattling sound.

Video: Start up rattle + idle at 2100RPM

KevinGary

Sounds like the dreaded timing chain guide and tensioner issue.

RangeK1D

Yes I was thinking that as well, the plastic guides and tensioners were a nightmare on the chain driven 4.2V8 ranging from the S4, A6, Allroad 4.2. But I keep reading everywhere that they had those issues figured out by the 07+ 4.2FSI engines, and some how these engines were to be more robust? Apparently not?

Jack88

Even if it is more robust, no engine is immune to those kinds of issues. It is rare on the A8, I have heard very few failures.

2010A8Lsport

I have the same apparent issue on my 2010 A8L with the 4.2FSI. I have noticed that sometimes it isn't there at all and kind of comes and goes... I was looking at it today and with the engine up to operating temperature the noise will disappear completely if I remove the oil filler cap from the valve cover. It stumbles for a second and them regains its idle.

RangeK1D

Agreed, I had zero engine related failures on my older A8. That engine roared beautifully.

RangeK1D

Wait so does that weird rattling sound exist on your engine even after startup? Because for me as soon as I start the engine that’s when it happens, but after a second it is gone.

I read something interesting in regards to a 4.2V8 on a Phaeton, apparently there is a service bulletin released by VW that states something like the following:

https://static.oemdtc.com/TSB/15-08-16.pdf

2010A8Lsport

Yes mine does it at anytime, in fact, mine is always silent at startup without fail., engine stone cold-warm-or right up to operating temp. The engine has to run for about 5 seconds before I hear any kind of ticking, which is the opposite from everything I've read everywhere on the internet. I should mention that I have done several oil changes and flushes, I've replaced both the anti drainback valve and oil jet with the valley pan gasket, performed manual carbon cleaning on the intake valves, pulled both high pressure fuel pumps to inspect the roller follower as well as pull the valve covers to inspect all of the cam lobes/followers/lash adjusters. None of them show any signs of wear and from everything that I've taken apart the engine is squeaky clean inside, no formation of sludge at all! I removed all of the plugs as well and they were also very clean. I pulled the oil separator, cleaned it and replaced the diaphragm inside it. After the O/S rebuild the ticking was much diminished but still comes and goes... my next step will be to remove the passengers side rear timing cover to take a look at the upper chain tensioners.

It has me baffled to be honest, the symptoms don't make any sense in that they come and go with no real rhyme or reason. Leaving the car running with the oil cap seems to completely elevate the noise.

Any help or insight would be greatly appreciated. I love the car but the noise it's making drives me nuts and could quite possibly push me to get rid of it, I feel as though I can't trust it to drive anywhere.

RangeK1D

I posted my issue on reddit; have a gander at the responses.

https://www.reddit.com/r/Audi/commen...medium=ios_app

From my understanding so far, the check valves are the root of the issue. When they go bad they don’t build the needed oil pressure and perhaps the tensioners suffer due to this. Chances are the noise we are experiencing now is due to the failing upper chain tensioners, which can apparently be replaced without removing the engine. I think I might source upper chain tensioners from JHM Motorsports and ask my mechanic to do it without removing the engine.

There is also a “15 second rule” that apparently applies to these 4.2 V8 engines. Have a look at this video discussing it:

Sci-fi_Wasabi

I had similar rattle on acceleration after 2-4k rpm in park.
Sounded like a diesel engine.This was a 2009 4.2L FSI (slightly different from the 2008 in that the intake manifold is 2 parts (upper and lower)
It did go away. I can't identify what 1 thing I did but here is what I did between the time it was there and went away.
1. Changed a dirty engine air filter (try this first).
2. Did a walnut blasting carbon clean.
3. Inspected and cleaned, but did not replace the anti drain valve (it looked perfect and was not sticking when i tried it out of the car.)
4. replaced the failed solenoid that controlled the intake manifold flaps, and various manifold gaskets.

Inspect the air filter first on this high mileage car, probably was not replaced for a while.