What's the Current Thinking On the 3.0 V6 TDI Timing Chains (CPNB)

[50pascals]

Hi all,

I currently have my engine apart replacing all of the cooling related components in the lifter valley. It has 193k on the clock.

I was researching something related to this repair and came upon many threads on "timing chain rattle." But the results and opinions seem inconclusive?

My car is a 2014 A6, I bought it used in 2016 with 32,000 miles with the CPNB engine. It made a rattle at startup then, and still does to this day. Doesn't seem to have gotten any worse. I assumed it was the cam phasers.

Being familiar with timing chains from prior cars, I started looking into the maintenance interval on these shortly after I bought it, but never found anything specific to chains or tensioners. In 2019, with 120k on the clock, I asked the service adviser at the dealer about it and they said they "do not have issues with those engines." Thus no need to replace it preventively.

Fast forward 4 years and I guess this is a "thing" now?

So my questions are:

1. How do you differentiate what the "bad" noise actually is?
2. Can you read a cam phase adaptation or anything like you can with the 2.0 gas engines?
3. Is there any data available in Vag Com that will provide a threshold for replacement
4. Has anyone done this themselves? Did it make a difference?
5. Who has the most miles without replacing the tensioner / chains? I've got 193,000 miles on mine

Thanks

P.S. - I own a shop, and the service advisor knows me, and generally always gives me good information.

 

[TurboDieselPoint]

My 2014 A6 CPNB has 120K miles. It has been problem free. I love this car.

It also has a mild rattle that will happen for a second or so after some starts. I find the rattle is worse if I leave the ignition on before starting. Hypothesis is that this is an artifact of the electronically controlled variable displacement oil pump (I think this engine has one), which might do something different if the ignition is left on. Perhaps a valve opens and it drains oil back into the sump?

I digress. Your question is one I have often wondered about myself. I hear the rattle—something which doesn’t fill me with happiness—but IMHO all the signs point to this being harmless. Seems like just about everyone with the 3.0 TDI has the sound, but I haven’t heard of a failure yet. I am further comforted by the higher mileage units (like yours) which have survived without chain issues.

Has anyone here experienced a real problem? Broken guide, skipped tooth, etc?

Different topic—what is your oil consumption? Mine uses oil pretty consistently at about 100 mL every 1000-1500 miles. A bit under 1 bottle every 10k miles. The consumption seems worse in the first 1000 miles after an oil change when the oil is fresh—perhaps volatile components are “gassing off.” That said, I wonder if the PCV needs replacing. I always find a bit of oil residue where the PCV exhausts into the compressor. Another thought I’ve had is that the 0w30 507 from the dealer is thinner than the previous 5w30 507 and causing consumption. What is your experience?

Thanks.

 

[mech644]

Chains stretching is a real thing on tdi touareg. The rattle you’re hearing at startup is in fact the chain and it stops once oil pressure activates the tensioner. This thread on clubtouareg is a decent overview, and it describes what setting in vagcom to check to see how the engine management is adapting to the chain stretching. https://www.clubtouareg.com/threads/3l-tdi-cata-cnrb-vcds-chain-stretch.298317/

My ’14 is at 178k, has been rattling at start for long time. About 15k miles ago I dropped from a 10k OCI interval to 5k. A lot of guys smarter than me feel that the oil blend that is correct for the emissions equipment could be causing chain wear. FWIW Porsche recommends a 5k OCI for the same engine when it’s in a Cayenne, go figure.
Im in the middle of replacing oil cooler, coolant valve, water pump, walnut blasting the intake ports, many cycles of intake manifold soaking in degreaser rod out with a dryer brush and repeat. Also replacing all idler pulleys, tensioner pulley, and alt pulley.
I haven’t checked chain stretch value yet, but will do so once it’s back on the road.

 

[TurboDieselPoint]

I agree with you about chain stretch/wear being a real phenomenon. That said, re-reading my reply, I see I actually made no mention of it while talking about the oil pump. The thought was complete in my head, but it never made it to my reply. I meant to say that, depending on its setting at start up and shut down, the variable displacement might cause oil to drain from the chain tensioner, or perhaps cause it to fill more slowly after start. This can make the rattle happen worse under some conditions. Of course, chain wear also plays into it.

That VCDS trick is handy. Thanks for sharing. I checked my CPNB and it is at -3.10 deg with 120,900 miles. Rattle happens maybe 1 out of 10 starts and doesn’t last more than around a second. Leaving the ignition on but engine off for a while will cause a start up rattle.

 

[dskeener]

My Q5 is intermittently making the 'chain slap noise' on startup. Glad to hear its viewed as 'harmless'. VCDS shows -3 degrees with 58,000 miles. I use a 7500 mile OCI which is about 1 year with current usage.

 

[PeterA1]

I'd like to input that I had my tensioner replaced when they did a rear main seal repair on my car, all under tdi warranty. 5000 miles later, still no rattle on startup. I'll come back here if it ever starts again, but I almost never let my car sit more than 12 hours without going on a drive and getting the oil all the way up to temp. Also I did all my deletes right as I hit that 120k mile mark so I believe that should help the oil quality

 

[Vindiesel6]

Anyone try using liquimoly ceratec during an oil change to assist with lubrication and aid in minimizing chain wear?

 

[arjax]

I notice a noise when it starts up, I am guessing it is chain rattle after reading this. So glad to know. I have to add a quart of oil at about 4500-5000 miles...once the car gives me the low oil warning again then I change the oil which is roughly around 6500 miles. When we first got the car, my first oil change was at 10,000 miles and I shipped off a sample to Black Stone. Iron and Nickle wear was a higher than universal averages. It was suggested to bring the interval down to 6000 miles. The second report showed better than universal averages for wear.