Hey all!
Recently I've been going over my '10 TDI (130k miles) after noticing the serpentine belt was looking kind of frayed on edges and the groove side was flattened out and cracking, etc., and realized I've not done any belt maintenance on this one yet. I could also see/feel that the idlers were all 'worn-in', which just means it was very obvious where the belt was running as it had begun a groove in the nylon idlers, etc.

As we bought it used in 2019, I didn't know when or if anything besides the belt itself had been done prior, so slipped off the serpentine belt to check the condition of idler bearing/wear surfaces fully and also for any play or roughness in the water pump bearings or pulley shaft. From what I've read, the S-belt is good for about 50k miles and then all should be replaced as a system with belt, idlers, tensioner replaced, which keeps A/C, alternator, and other accessories reliant on belt tension working efficiently, and as-designed.

While your mileage may vary, I found that all my idler pulleys were needing replacement due to rough/noisy bearings/worn surfaces and the water pump shaft I could wiggle a bit, and in turning it there was an obvious 'catch' point in the bearings on it. That meant the belt tensioner was going to need replacing too, as we've put 45k miles on this car since purchasing used, and so I began looking for complete 'serpentine belt service kits', which have all idlers, tensioner, belt, and usually the hardware too, but sometimes not. The water pump is sometimes included in 'built kits' you can find on FCP Euro and ECS Tuning for example, but is generally excluded otherwise.

You can definitely build out a kit too using the OEM (INA idler pulleys/INA tensioner/Continental belt) sourced parts or an find an INA service kit for your engine. I sourced the INA service kit for my belt-driven HPFP, which has the cogged belt, metal idler pulley, and circular belt tensioner required for that application. On my S-belt system, I found I could source the OEM, INA parts individually between Rock-Auto and FCP Euro, along with other parts I was ordering, so that saved me around $80 over buying the Continental serpentine belt service kit, which comes with INA Idlers and tensioner, and a Continental S-belt...go figure. Audi is happy to supply you those exact same items in a factory branded OE box, and stamped with Audi rings/part #s, but it'll cost you.

Key takeaways:
When pulled the old parts off my '10 TDI engine, every one of them (except the two actual drive belts) were OE parts stamped with production dates of early 2010 or late '09, which I found shocking, especially on the HPFP that Audi dealership had changed under TDI warranty @87k miles; apparently they just slipped a new cog-drive belt on it and called it good...yikes!! Same with water pump, and inside the water pump on my TDI was a metal, open style impeller, which is generally highly reliable design...it wasn't leaking, but the bearing were going out on it, so that was not far off.

If you are servicing an older Q7, there is a changeover date as concerns the belt tensioner's primary bolt, a T2Y type stretch bolt, which you need to replace, so be careful to get the correct bolt, which was inexpensive at only $2, for mine. New idler pulley bolts, on the other hand were eye-wateringly priced and not even stretch bolts, which makes zero sense to me, but I didn't need them. Again, a complete belt service 'kit' will often include the hardware, which contributes to higher pricing if it does, but it is convenient.

The smaller anchor bolt on the pneumatic tensioner and the idler pulley bolts did not require replacement on this Gen 1 TDI, as they were all of modest torque values spec, but always be sure you verify for your engine year/type, etc.

While the S-belt was removed, I also verified the splined pulleys for alternator, A/C compressor, and power steering pump, and found them fouled with bits of the old S-belt and a few tiny pieces of rocks embedded in that, so used an angled pick to trace through each groove in those pulleys and clean them out so the new S-belt would fully seat on them and not be prematurely worn or get thrown off.

Bottom line is don't take your belts, idlers, tensioners systems for granted, as this TDI was 100% serviced exclusively by Audi dealers up till we bought it, and yet even whey they replaced major components, such as the HPFP, they didn't replace the idler and tensioner for said drive belt. Likewise on the S-belt, the guidance is to replace all idlers and tensioner, but that wasn't done either; they just slapped on a new S-belt at some point.

Doing these services (HPFP drive belt/idler/tensioner) and the water pump along with S-belt system full replacement got rid of all my odd noises, and as a side perk my A/C system is working super great now thanks to clearing the obstructions on all pulleys and the new drive belt & belt tensioner, which is timely coming up on Summer months. I'm sure the alternator/battery/power steering pump all benefited from this, but the A/C is what we feel inside the car, and so that's what counts, right?

From what I looked at on the internet, most companies that sell the idlers and tensioners under their owner banner are basically just repackaging the original part like Audi does, which is made by INA, as I could see the largish, very distinctive INA brand stamped/molded on the tensioner and bearings of the parts pictured. So I just looked for best price for the actual INA bits. Can anyone explain why a brand new, made in Germany, Continental S-belt I paid $25 for...why Audi lists for around $100 or greater? There must be a lot of cost in repackaging an item and stamping a diff part # on it, LOL.

Is your Q7 ready for SUMMER?!?!?!?!

 

I condition my serpentine belts (plural due to multiple vehicles!) every year during AMW (Automotive Maintenance Weekend, also known as "4th of July" or "Independence Day Weekend" in some circles). In doing so, I'd say that the belts themselves tend to last almost indefinitely. However, I replaced my Q7's original belt at somewhere around 125,000 miles due to the failure of the alternator that seized and caused physical damage to the belt. While I possibly could have continued to use it, as it "looked okay," I took your advice of not taking it for granted. At 155,000 miles on the Q7 now, I agree that the bearings in the idler pulleys have definitely seen better days. They are on my list for this year's AMW.

On my other daily drivers, I still have the original belts on the 2018 Crosstrek and 2013 Forester at 99,000 and 150,000, respectively, and both look just as good as new (aside from the print on the smooth side being worn off!). I pull the belts off, roll them up, and soak them in 303 protectant for about ten minutes.

 

Kudos to @-Wes- That's a really good tip related to the 303 protectant product.

I haven't used that product yet, but it's on my radar...I'd better write it down on the to-do list, LOL! I have heard about it though from couple other mechanic type sources and seems like an excellent product and one I want on my shelf to spray down CV boots, steering rack gaitors/boots, strut/shock protector boots, and pretty much anything made of rubber beneath the car. It's like ArmorAll for bushings...helps keep them from oxidizing and cracking pretty much. Still, everything that's a wear part will fail eventually.

Just for the average reader though, it's super important when you remove a drive belt to mark the direction of install/rotation (like an arrow pointing to engine side before removing it), when their is no visible indicators on it to snap a picture of as a reminder of which way it has to go back on the car. Remounting a used drive belt opposite of how it came off the car is normally going to result in accelerated degradation and/or failure of the belt, and of course anytime a drive belt is removed is an opportunity to assess condition and swap out as those don't cost much...unless you buy them from Audi! (Or you live in Alaska!)

Other common issues on the Q7 that will damage and often cause drive belts to fail are oil leaks and coolant leaks, which degrade the rubber, etc., so just file that info away for later use.

Thanks WES! Great tip on the 303 protectant use as a drive belt conditioner/protectant.

 

Interesting thought about the directionality. I have never paid attention to that, so there is, of course, a 50% chance of putting it on the 'wrong" way. Perhaps the consistency of timing and, in most cases, the associated miles, makes it less likely to be a wear concern? I don't know, but I'll keep it in mind for this AMW. My primary use of the 303 protectant is for my tire sidewalls. It makes a notable difference with sun exposure degrading the rubber. I also keep tire chains in all of my cars, and a couple of them, such as my Audi and plow truck (a '76 F250), I also keep a set of EDPM bungees to help secure the chains due to their use in more challenging environments where the wheels are likely to spin on ice surfaces (such as snow plowing or vehicle recovery). The built-in binders on the chains just aren't up to that level of stress. However, untreated, the EDPM straps usually only last a season on the plow truck before they are falling apart, and, at times, even breaking. Treated, the plow truck straps will last six or seven years, and the straps on my Q7, which are... eight years old now, still look like new (though I rarely have them in use for more than 48 hours consecutively due to the need to drive the vehicle on the highway).

With regard to tires, those on my 1969 C20 pickup are 28 years old now (shockingly....! I had them installed in July of 1997). And, with annual treatment with the 303 protectant, they still look pretty darn good. I only started using the stuff toward the end of the aughts when the availability of tires in a 16.5" rim size essentially evaporated, and the tires essentially look the same today as they did at that time. I even use the C20 to haul loads of 3500-4000#, and the tires just keep soldiering on! The next time I get tires for that truck and my '76 F250, I will need to replace wheels at the same time to a 17" rim to fit the available tires. Sadly, I know that day is coming very soon, but at least I can still get molded steelies that will allow me to use my original dog dish hub caps.

 

wonder have many people here are willing to spend that money on that kind of service. Whats the total tally for the parts alone?

 

My drive belt failed and it left me stranded and in need of a tow. Cause was a screw backing out and shredding the belt.

 

That all depends on how/where you buy your parts and whether you DIY this or take it to a local shop.

As stated, I sourced a pre-packaged INA service kit for my Gen 1 TDI's HPFP (sits on front of engine), and INA is the OE supplier.
NOTE: Very Important!! Use only the central bolt head (13mm IIRC) to remove / install this circular tensioner...not the hex fitting on it; that's only for adjusting the tension during the installation.
There were no instructions for the tensioner install...just the parts; I had to look it up in my repair manual to install and torque this tensioner (and the idler pulley) correctly, which is a multi-stage, defined process. It's the HPFP, so kind of important to get it right the first time...don't just 'wing it'.

This is the 2010 Q7 3.0 TDI HPFP Service 'KIT' I bought (includes the tensioner, cog belt, idler pulley, bolt):
INA ZD0585K Timing Belt Tensioner $ 72.79 $ 0.00 1 $ 72.79

With a shipping fee & tax, this full kit was $90 USD @ Rock Auto, which is much less than just buying the tensioner on most sites, so good search/ shopping is key as these individual parts and the full kit can otherwise be semi-expensive depending on where you buy them from.

Here's my order data for the S-belt, all idlers, tensioner, and a new water pump, which I sourced from Rock Auto ( the blue links) and the last two items from FCP Euro. My all-in costs for S-belt service w/o the water pump, was approx $140 USD in parts + local taxes/delivery, so pretty inexpensive if you shop well.
With the new water pump bundled in, $168 in parts...etc.

2010 AUDI Q7 3.0L V6 DIESEL Turbocharged (S-Belt parts + Water Pump)
GRAF PA979 Water Pump $ 27.79 $ 0.00 1 Net= $ 27.79
INA FT40356 Belt Tensioner $ 64.99 $ 0.00 1 Net =$ 64.99 (This is the pneumatic type belt tensioner that looks like a tiny shock absorber)
LITENS 900677A Idler Pulley $ 18.28 $ 0.00 2 Net =$ 36.56
INA 5320160100 - Splined Idler Pulley - $9.99
CONTINENTAL 6PK2475 - Drive Belt - $27.99

The new stretch bolt required for belt tensioner was $2 at FCP Euro and I had to chat with them directly to get the correct part # for my VIN on that bolt as there is a parts split in mid-2010, but they don't tell you what changed...apparently it was the tensioner's T2Y 'stretch' bolt diameter that changed in late 2010, as all the other part #s were the same.

Again, these are for my specific engine, so your mileage may vary on which part #s you require for your model year and engine,

If you don't mind paying extra for the convenience, just find the service kit prebuilt...everything for the S-Belt system service in one box, but be sure to verify new hardware needed related to the stretch bolt on the tensioner. My benchmark price (lowest found) for the Continental S-Belt service kit was $225 USD. Clearly, I paid less than that for the exact same parts and also got the water pump I needed.

Didn't have any clue the water pump was on the way out for a dirt-nap until I checked all the idlers and pulleys on the system for wear/deflection/play, smoothness, etc. It's super easy to do these checks and takes very little time to do it, but you just gotta put it on your schedule and do it to see how things are with your Q7. Maybe you don't need idlers or water pump, but then again maybe it does. Won't know unless you check. I slipped the belt back on afterwards and went online to look for the parts I needed.

 

You are probably just 'living right' and overly generous with soaking your belts in the 303 protectant, IMHO. Better not tell the wife how good that stuff is at anti-aging benefits.

It doesn't matter which side of belt is 'out' when you put them on car the first time unless a belt is marked to only rotate one direction. I always install drive belts so I can read the label or part numbers printed on their outer/ smooth side, and I'll position the label on belt on top pulley/drives (like at water pump) so it's right in front of me during install, and that's my reference point.

Once an S-belt or cog-type belt runs-in it gets operationally stressed, stretches a bit, and if removed for services it needs to go back on same way it came off to keep the stress load applied to belt in same direction (or force vector), etc. Flipping belt around opposite changes the stress load vector and weakens the drive belt at structural level, and if you got wobbly idler pulleys and such going on that just hastens the belt's demise.

 

2011, 180k, I've replaced the serp belt a few times, tensioners/idlers never. I give them a spin from time to time.

A better question for all the Gen 1 and 1.1 guys- when did you last replace your HPFP toothed belt, tensioner and idler?

 

whats a gen 1.1?