Gary Knox

I want to replace the belt on the front of my '07 A8. This is the ribbed 'serpentine' belt, but on these chain drive cam engines, the only item it seems to drive is the alternator - IF I recall what the underside looks like correctly!!

Have any of you done this service on the direct injection engines, and if so, can you give me a bit of guidance? Releasing the tension seems the biggest issue as I examine it.

THANKS for any suggestions.

MP4.2+6.0

No direct experience, but you are using new OE/OES belt, correct? Paging Mr. Bally...

mishar

Tensioner has a square hole where you should insert a breaker bar and turn clockwise to release the belt.

Gary Knox

Mishar,

Thanks for that advice. Should I also change the tensioner pulley when I install the new belt (75K miles on the '07 A8). I'll be using an OE belt from AudiUSA.com, or a Gates belt (used their timing belts on my Porsche 928's, and always performed well). Any comments on those options?

MP4.2+6.0

I would skip the pulley in this (narrow) case. I recently made the same decision w/ my W12. 2006, with about 105K miles at the time. It has a very circuitous serp belt more like the prior port injection 4.2s, but with no timing belt lurking behind akin to the FSI's. Very robust serp. belt too--for the W12 anyway, using my 2000 A6 4.2 as the comparison. W12 serp. belt is grooved and soft felt type covered on both running sides. Pricy too.

I checked pulley (and water pump--why I pulled belt to start with) very carefully. 99.999% worst case if this belt fails, you call the tow truck. Unlike timing belt, you don't bend valves. It's comparatively easy to replace something like a pulley anyway if the need ever arises. In this case, if you were at like 150K, or heard any noise from the area, then I would do the pulley. Thus, likewise I opted for (audiusaparts/dealer) belt on mine, but no pulley or other stuff at this time. Having done it, but for the fact I suspected a bad water pump (turned out it was the hose connection right above it that I couldn't see until belt came off), I can now basically agree that at least the W12 serp. belt does essentially seem to be life of vehicle if other work not needed anyway.

Gates as alternate: agreed that is also a rational/essentially OES type choice if available for your fitment. I would not use any no name/name du jour stuff--hence my original reference. Mister Bally will certainly attest to that w/ his port injected 4.2 tale on the side of some road.

mishar

As MP said, if there is no sound of a damaged bearing I wouldn't replace it.

Gates is good. I just replaced tooted belt on a CNC lathe. It was Gates. If their products are good for industrial use they must be good for us.

Gary Knox

OK, thanks to your great advice - MP and Mishar, I'm ready to go. I know that Gates is the OE supplier to Porsche for the timing belts that the Porsche dealer sells with the Porsche part number (at about 2X the price of the identical Gates belt, of course), that's why I use Gates when doing a timing belt change on the 928. I've got the gates part number, so I may see if the local Gates dealer can get one.

Thanks again for being so helpful

MP4.2+6.0

GATES Part # K050448 {#25050448} Micro-V AT Premium OE V-Ribbed Belt; K05 21/32" x 45-3/8" $14.80 Can't link down into the listing, but just go to the site.

Gary Knox

MP4,

GREAT - thank for the info. I hadn't 'thought' to look on their web site. It's now on order.

Mister Bally

Be sure the belt you buy is a genuine Gates. If it seems too low a price to make economic sense, it could be a fake. Consider buying from a dealer or well known auto parts source (NAPA, Pelican etc.) There are bootleg Gates belts out there.
Whatever you do, don't get conned by a certain "Blue" organization that uses slick marketing blurting out words such as "OEM Quality" or "Genuine OEM source" parts which has been proven to be a complete lie.
Use advanced search for a thread I started titled "Road Trip Emergency" for my serpentine belt saga. Then there are my timing belt threads....