dvs_dave

A popular topic of discussion on here, (like ATF) but again one that is subject to a lot of misinformation and rhetoric. So I thought I'd put together something to try and shed a clearer light on the topic.

Audi USA recommend a timing belt service (incl. all rollers, tensioners, waterpump and thermostat) every 75k miles or 5 years, whichever comes first. The 5 year stipulation for some reason is not called out by Audi USA, but is in other markets, for example the UK

Many people baulk at this service interval and say it's too early and should be closer to the 100k mile mark as it used to be for older Audi engines. However that's often said without considering that older engines were lower performance, lower revving, and ran at lower temperatures. Although owners who have made that call themselves report that having made it to 100k miles without incident, the belt still "looks fine". The thing is with EPDM belts (as used by Audi), they generally show very little signs of obvious wear or deterioration when compared to older style neoprene belts. For example they generally don't crack and perish, even after many miles and years. However they still wear out, although not obviously.

Here is a piece from Gates, one of the OEM timing belt manufacturers on EPDM Belt Wear Diagnosis.

In short it's not really possible to tell that the belt is worn from a visual inspection alone in a normally performing system. Gates themselves recommend replacement of their products between 60-90k, or depending on manufacturers recommendation. I doubt it's a coincidence that the Audi interval of 75k is right in the middle of that range.

In reality, it's unlikely that the belt itself will fail unexpectedly if the timing service is delayed. Usually one of the rolling components will fail, such as an idler pulley, tensioner, or water pump which then overloads the belt and causes it to fail as a consequence. Once again, it's not really possible to accurately diagnose the condition of the rolling components with the timing belt in place, unless it's obvious, such as a leaking water pump, noisy roller, weak tensioner etc.

Hopefully this information is useful, and I hope it makes you think twice about delaying the timing belt service as, unless you're planning on moving the car on, it's something that has to be done sooner or later, and the consequences of not doing it can be severe.

And for good measure, here's some horror stories and some gory pictures to get your teeth into.

• https://www.audiworld.com/forums/a8-...e-wtf-2616464/
• https://www.audiworld.com/forums/a8-...-work-2882133/

MP4.2+6.0

The interval was 105K miles on the C5 and D2 4.2, until Audi retroactively changed it to the present 75,000. That motor is very similar to the D3 4.2. In between those recommendations, Honda USA wrote some very large checks and extended warranties due to a lot of belt breakage on their larger motor--many, many millions of dollars. My dad got a retroactive check on their Accord (mid 90's vintage) in the small world. Audi had carefully repositioned its various warranty and service coverage to avoid the 75K mile overlap before it announced the downward change. Conspiracy theory maybe, but timing/juxtaposition has always seemed odd. They didn't have to write the checks Honda did. Old Audi 5000 stuff aside, Audi seems to have gotten prickly and sensitive to warranty and litigation issues; the sunroof drains being one example, MAF's a minor one (pre D3 for that). In plain English, move of the service interval here may have been influenced not just by technical subjects, but perceived litigation risk.

The C5 RS6 4.2 interval was actually only 30,000 miles. If you search old posts, Audi did NOT cover anything but the belt there--a little hard to square with the replace all the components as recommended by Audi notion. OK maybe "only 30K" so "no need to do the other stuff." But, the issue came up again for CPO RS6s when the 60K interval came up and they had bought extended AudiCare. Same answer. And more on point, IIRC correctly it actually came up for a few with D3 4.2's. Those fell into a weird exception where Audi once had AudiCare out to 75K miles and it only applied to CPO's if you bought the coverage--AudiCare says it covers everything on the maintenance chart basically. The coverage price was idiotic from Audi's perspective, but they actually wrote it--I paid $690 for my W12 (same price as a four banger!) for thee years of added service, including the second major interval. Mine had no belt though so I didn't need to push that subject. As I recall in this specific fact pattern with a 4.2, the result was Audi did not cover except for the belt. Now very hard to square that with what Audi supposedly says on replacing the other parts. The service book does not mention anything but the belt, and never has AFAIK. In there is where tons of confusion has always been on exactly how much to replace as part of the job. Saying it more strongly, I think it is factually incorrect to say Audi recommended more than the belt itself (as in, actually covered per its maintenance table) when you go to the actual 4.2 history. What "they" may say today now that they are off the hook for any cost could have changed, but I would separate out the dealer/service writer recommendation from the Audi company technical one. I'm not arguing at all to do belt only (and do many more components myself), but just trying to separate out Audi's actual recommendation and related confusion.

The way the maintenance table is framed is why Audi said it would cover belt only when the owners pressed it. A nice little twist too, extended AudiCare is also now back for out to 75K miles (and now not just CPO cars), instead of the 65K it was when they had cars with belts commonly otherwise eligible for coverage. And there was one last belt engine left in Audi's USA offering as I recall by the time this changed again--one of the 2.0T's that was now back out at...105K, exactly where the 4.2 started. Hmmm....

I respect what you are saying about top drawer belt manufacturer recommendations too. But like with the Audi recommendations about what to replace --which I think are really coming from servicing dealers, parts vendors and boards rather than Audi--I think it's important to recognize the recommender motivations and factor it into the analysis. A belt manufacturer and a servicing dealer and parts seller are motivated to sell more of their product, (as is a ZF in the transmission fluid context BTW) or a dealer who reports very religiously on need to do brake work and maybe skips over the actual wear numbers unless pressed. At the margin, you get what you incent.

To me it comes down to risk vs. cost and hassle. I can get my body scanned constantly too, or go in for the dental hygienist every month or get my hair cut every two weeks, or bleed my brake fluid every 6-12 months, or... But we make choices. Because the risks are catastrophic here, each time I have dealt with a belt or had it off for some other reason (both 2.8 and 4.2) I have been prone to replace it and much of the ancillary gear. But realistically it is probably a sub 1% failure type category at any rational service interval miles. The economist in me says the rational economic answer is a fair amount longer interval. But most of us--me included--tend to buy insurance when we don't like the "tail" risk being insured against. And yeah if I had a gung ho drill sergeant or was graded constantly on grooming where it mattered for promotion or pay, I might get my hair cut every two weeks too.

mcs

Audi Australia reduced the timing belt service from 120,000 klms (approx. 75,000 miles) to 90,000klms - 56,000 miles. It is in my service book.

They don't say why either.

This seems a little low.

03_AR_CO

I like to do as much as I can myself. I have always, not exactly always but in recent decades bought Audi's out of the warranty period. I have done timing jobs on the inline 5's and 4's V6's and 8's. I usually go marginally beyond the recommended interval, as I don't really beat my cars, drive them spiritedly but not exactly rough on them either. I most often do the majors shortly after purchase, and replace every roller, tensioner, water pump etc when I am in there. Anything that is easier to get at while I have things apart I replace as an insurance policy, as well as having a flat starting point on my car. I just purchased an old 01 TT with 120k on it and did the timing, valve cover gasket, plugs, coil packs, all of the vacuum system, and breather system, cam position sensor as I had a new one laying about, coolant temp sensor, O2 sensor, MAF, dip stick assembly, gear box oil, diff oil, haldex oil and filter, fuel filter, cleaned the engine and compartment, oil and oil filter, coolant flush, brake fluid flush and more. It runs like new and will for a long time to come. I bought it at the right price knowing I would spend time ans $'s up front to get it where it needed to be, did the same with the W12 and the 4.2. I cant afford to be reliant on an independent never mind the dealership to have my cars in the condition I want and need them in.

So as far as the rant goes (and my last hair cut was months ago :-) at best by the way, I have no drill sargent here, replace all that you can yourself when you begin any major job. It is really much more economical, I have had few disappointments with this method, and would recommend it to others.

Mp4.2 keep up your posts, I enjoy the hell out of them, I have learned a lot from you and you have helped me a great deal by doing so.

dvs_dave

That's interesting. I wonder if Audi vary the service intervals depending on actual environmental factors, or just adjust it to what they think the market expects and will stand.

I'd like to think its for genuine reasons but the cynic in me thinks otherwise.

For example, adaptive service schedules cannot be enabled on US market cars, but it's the norm on Euro models. I'd much rather adaptive as it actually accounts for your specific use, not a one size fits all fixed interval as it is now.

I guess it stems from in the U.S. there is still some weird belief that you have to change the engine oil every 3k miles regardless. That's what old Grandpa Sam did with his 57 Chevy, so it definitely needs to be done in a fancy shmancy uuurrrpppeeennn import, dag nam it! Certainly does no harm, but modern oils can do way more than 10k, especially in a car that does mainly highway miles.

MP4.2+6.0

Again per my prior theme, you get what you incent...

I will use BMW as the poster child case in point. My Mini with their "CBS" system (condition based service) reports to me its turbo engine that puts out one of the highest specific horsepowers per liter for production vehicles of the era needs an oil change every 14-16,000 miles. Of mixed highway and a lot of quasi urban driving, and a fair amount on short cycles, all on the Prinz engine of dubious quality and with some history of turbo oil line issues and a key engine component in the oil circulation system known to literally unscrew. I think not. Not an outlier case by any means--known as the norm on Minis and not uncommon on BMW's apparently either. And BTW, maximizing the hassle, the oil reports on variable cycles, but plugs, other filters, etc. remain fixed (many of which fall outside their "free" period).

Well, why would a manufacturer be "incented" to do this? Lets see:

• In Europe they have gone longer than the U.S. on the old 3K American oil change of yore (I'll skip the Japanese diversion; often shorter cycles than modern Audis). Not controversial so far.
  
• Europe has gone way deep on enviro and carbon footprint stuff. Audi reports on it at length in their annual report. Where I found the only discussion of why they went to G13 coolant--never in a technical document anywhere. It was all carbon accounting. Look at your car oil filter sometime. Anybody really think that plastic outer container set up that helped the carbon and metal accounting I guess really makes sense with all the solvents and rags that get used compared to old spin on; the spin on that was on my C5 4.2 BTW. Interestingly, spin on is back on my Hybrid but I suspect that also allows them to move to suctioning the oil from above (filter is high and in front) and never touch the belly pan--and get a look underneath for better long term checking for leaks and other service issues.
  
• Perhaps the biggest, and pretty clear with BMW/Mini. If you offer "free" maintenance, you are incented as a manufacturer to minimize it, whether it is technically sensible or not. BMWs don't have great cost of ownership numbers long run, but the sense is they game things like this to "goose the numbers." "Condition" based service here seems to mean their financial condition, not my vehicle's. Baloney.

I agree with you in using variable systems actually, and our North America cars have the sensors there for it and have since the millenium. But they can't be enabled AFAIK. Having seen the variables Audi seems to track (via VCDS), theirs looks technically thought through. However, I also want a manufacturer who doesn't play games with when it reports out the service need--true "truth," from a bona fide engineering and owner cost perspective, not a carbon or cost of "free" maintenance bean counter. You get what you incent, for better or worse. And in 20 years BTW both your electronics and hood will probably both be screwed down for good, since "they know better." Scary.

seamore2001

To the point about replacing other rolling components along with the timing belt: After buying my '06 A8 this past January I spoke with the dealer service manager about the maintenance history of my car (after getting past other front line no-nothings in the service department who claimed there were no records of my car - but that's another story). Audi Care covered the replacement of the timing belt, but not the water pump at 73K miles. Now with 125K miles on the car, I'm nervous that while the timing belt will make it to ~145K miles and the next replacement interval, the water pump and other components may not, leading to failure of the entire system. For piece of mind I suspect I'll end up replacing the TB early in order to also get replacement rolling gear - sometime in the next few months.

It's frustrating to discover that a few simple aging components that should have been replaced during the big job of TB replacement were left in in order to save a couple of hundred bucks.

uberwgn

Hanover, December 2009

aTOMic

This subject has been beaten to death here and everywhere interference engines are discussed.

I am pleasantly surprised no one has whined about this fact.

I don't mind beating (almost) dead horses as important as this one. Especially with well-cited sources, as in this thread.

Good thread, mates!
-Tom

Leveret

I think some belts are more prone to failure than others. I am of the 'if it works don't mend it' school of thought. I think a belt will last the life of the engine if the things it drives don't seize. Our 2.8 A6 had 135,000 on the original belt (I bought it at 77,000) when I sold it at 15yrs old. It had an easy life, driving two short cams, each of which chain-drove another cam so no sudden loading. The water pump was driven by the flat, not toothed side, so even if you didn't notice leaks or squealing for a bit it probably wouldn't break suddenly. Also, being V engine it is a long belt which would probably wear less than a shorter belt on a diesel engine. Anyway, I just used to inspect it every 10k or so, bolstered by my experience of an even older VW Passat whose belt was still going strong at 240,000 when I sold it.