# W12 Timing Chain and Serpentine Belt



## baby_cota (Jun 12, 2012)

Does the timing chain on a W12 ever need to be replaced? Also, at what mileage do you replace the Serpentine Belt?

Bill


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## PanEuropean (Nov 3, 2001)

To the best of my knowledge, there is no service interval for the timing chain - it should last the life of the car.

For the serpentine belt, perhaps see the discussion in the Phaeton Forum 'Table of Contents' (FAQ by Category) about Maintenance and Service Schedules - it is the first link listed on post #5 in the FAQ.

Michael


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## PowerDubs (Jul 22, 2001)

The timing system on the W12 is very similar to the VR6 engines.

It is not the chain itself that could give an issue, rather it is the plastic guides the chain slides on.

Eventually, they wear out (a groove gets cut in them) and the tensioner that presses the guides against the chain can only adjust so much that slack occurs in the chain.

The early 12v VR6 needed the guides replaced around 100k. The newer 24v VR6 (of which the W12 shares it's cylinder heads) don't have that issue.

My 2003 GTi 24v VR6 has over 200k on it's original chains and guides (and everything else outside of the water pump and muffler, not counting normal tuneup stuff). The car runs as good as when it was new. Better actually since I had the ECU reprogrammed. 

The extremely few people who ever need to deal with the chains on the 24v VR6 seems to me to be from not changing the oil as often as they should.. which makes sense- dirty oil is abrasive.

SO, keep up on your oil changes and don't worry. You'll hear the chains being noisy long before they ever break and ruin the engine.



:thumbup::beer:


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## baby_cota (Jun 12, 2012)

Thank you Michael. I read that post but I don't see anything about replacing the Serpentine belt on the maintenance schedule.

Bill


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## PanEuropean (Nov 3, 2001)

Hi Bill:

If it is not listed on the maintenance schedule, then it is an 'on condition' item, which means that it doesn't have a fixed replacement schedule. In such cases, the VW technician who does the regularly scheduled service should inspect the belt and see if it is showing any signs of wear (typically cracks).

My VW dealer replaced the belt on my W12 engine a few months ago - the car was in for a whole bunch of other service, and I asked the tech to look the whole car over with a microscope. He found evidence of wear on the serpentine belt - tiny cracks across the belt - and out of an abundance of caution, I asked him to change the belt.

I don't think that the belt itself is hugely expensive - I can't remember what I paid for it, I think it was probably about $100, more or less. It is difficult to get access to the belt to change it - so, anytime service is being carried out that involves sliding the front bumper and the radiators forward to the "service position", I think it would be a good idea to take a close look at the belt at that time, and change it if there is any evidence of degradation.

I have less than 90,000 km (about 55,000 miles) on my car, but the car is nearly 10 years old, and I think that "calendar time" is a factor in degradation of rubber parts like this belt, in addition to hours of engine use.

Michael


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## PanEuropean (Nov 3, 2001)

For the record, here is a picture of the engine from my car, with the serpentine belt on the front.

The engine was removed some years ago to change an o-ring in the torque converter.

Michael

*Serpentine belt - W12 engine*


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## Paximus (Aug 26, 2011)

Michael:

The images of your removed engine always make me gasp! It's such a far cry from the tiny 4-cylinder engines in the cars I learned to drive on.

Also amazing is that belt-drive technology is still such a reliable staple, even a few hundred years after its hey-day. However, from the image of the 4-cylinder engine below we have miniaturised it a bit...! 


Chris











image via American Textile History Museum, Lowell, Mass.


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## invisiblewave (Sep 22, 2008)

Those shots always remind me of some sort of exotic wild beast that David Attenborough has managed to photograph after 3 weeks of camping in a hide.


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## PanEuropean (Nov 3, 2001)

invisiblewave said:


> Those shots always remind me of some sort of exotic wild beast that David Attenborough has managed to photograph after 3 weeks of camping in a hide.


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