MP4.2+6.0

Some tips for W12 owners to look at.

I did a plug change recently since I had to take the intake off anyway to get enough access for a rear cam positioning sensor (see separate post). I will skip the plug specifics here, but note some OTHER things I found.

1. The front oil vapor plastic hoses had issues--the ones at the extreme outer corners of the intake manifold, just underneath. The driver's side one showed signs of some oil stains around the hose, and when I pulled it it broke in two basically. The passenger side one had some suspicious tape on the outer jacket which has to have been applied by the dealer previously (who did prior two plug changes). Sure enough, when I got the new parts, I cut that one open and found it had been spliced back together as a repair, just as I had done temporarily on the driver's side one. Parts 07C 103 641 L and K. About $77 each at discounted dealer. Needed to be done given one was clearly broken and the other serviceable but patched. Both were stiff/brittle too; the new ones were not very flexible either, but certainly more than the old ones; basic high heat soak/bake over 8 years/100K miles with constant oil vapor.

2. The rear plastic wire routing piece where the O2 sensor cables for the passenger rear sensor and both of the drivers side sensors was broken in various ways, and by the time I was done, more so at the bolt down point. Audi calls it a "conduit." You could jury rig it with tie straps, but I sprang for the discounted dealer $13. 4E0 971 803.

3. There is a weird electrical connector at the extreme front of the passenger side W12 ignition coil wiring harness. It seems to be a wire terminator, with apparently a jumper between the two terminals fitted on the end (no wire emerges from the connector and nothing has been torn loose). Also, somewhat behind it, one of the ignition coil connectors can get stuck under some of the oil vapor stuff bolted to the underside of the intake manifold...ask me how I know. In both cases, the OE set up is a push pin type insert into a drilled hole and then a tie down strap run through that. Tracked those down too. 8E0 971 818B. $1.12 each discounted. Looked handy for other Audi applications where you need to secure something and have a hole to locate the tie strap with. On the W12, you could use standard tie strap for the extreme front one in a pinch, but the rear one involving the coil connector really needs that push in tie strap in place to avoid getting the wiring harness jammed between the oil vapor component protruding from the bottom side of the intake and the valve cover just below it--only about a 3/16" separation max, and the wire naturally wants to run exactly there unless the tie is in place.

4. W12 air box alignment issues; likely similar on a D3 S8 with its likewise twin box set up. The drivers side box on mine never seemed to align quite right. I complained to the dealer several times during warranty or service and they would try to realign it. The trouble was the cold air intake would not meet up at the air box exactly right, and you could see an open crack at a push fit duct component where it probably pulled in some hot under hood air--the part that has some bellows type ridges to it. After looking at it yet again, I decided maybe this rectangular shaped flexible ABS type ducting piece was somehow warped --it runs between the front of the air box and the grill air collector area. When I got the new one and lined them up side by side, i could see maybe 3/16" distortion in various dimensions. Sure enough, with new one in, the box finally lined up correctly to the air ducting for the first time in as long as I can remember. Part 4E0 129 628M for US drivers side, $28 at discounted dealer price. Passenger side would be 4E0 129 627M.

5. Little rubber grommets that hold that center intake manifold W12 decorative trim cover down. There are three smaller ones, and one bigger one. You can read the part #'s on each if you look very closely. Replaced another small one, which was torn. 07C 133 588G. $3.42.

All these parts, and some help tracking a few obscure things down, came from AudiUSAParts.com Like other W12 one off stuff, a few came from Germany, but as usual that was only maybe an extra week. I had done the original plug job earlier and ordered the parts. When these parts arrived, I just bolted them in, pulling the upper part of both air boxes to get at some of the relevant parts again.

Not on this pass, but previously I replaced both MAF sensor connector ends. 1J0 973 999A. Currently $5.49 each. Once you get the hang of how the connectors are assembled for the little wire pins and you basically cut and shatter the old plastic to get them out cleanly, it's fairly straight forward to change a connector end with no wire splicing or crimp on stuff. In both cases, I guess over time the dealer broke the locking tabs during various service and warranty items. Those of you w/ W12's know these are very close to the headlight units, and getting the upper air box half in and out is pretty exacting/finicky/trial and error. These connectors often seem to either get in the way or be in the wrong place when putting the boxes back in. Obviously a potentially loose connector on an MAF is not a good thing.

03_AR_CO

I have the same issue you describe with the driver side air box meeting the cold air intake duct, I had been planning on replacing it, and after this read I will absolutely do so, and easier for me now that I have the part number, thanks again.

Bangerla

You also might want to check your coolant lines as well. So far on my W12 two of the coolant T's have broken, and the quick connect coupler to the thermostat was rotting away as well. All the plastic parts in the cooling system seem to get very weak and brittle with age.

MP4.2+6.0

Agreed on water line stuff. I didn't detail it here, but I have previously replaced the overflow bottle hard plastic line that runs from the reservoir bottle toward the radiator area and toward the back of the motor. Another W12 poster and I exchanged e mails about that last summer. You can splice it with rubber hose and some clamps--another kludge "repair" I found dealer service apparently did at some point, but as you say it gets brittle w/ age. Same molded plastic line is on my 2013 Q5 BTW, so this is not some W12 oddity w/ newer Audi models.

When I open the cooling system, I replace the O rings at the main connectors. There is a smaller hose near the main lower one on the drivers side in the lower corner of the radiator where the seal is not available as a separate part. When I did a coolant change recently, I found what seemed to be a minor leak there, at least when I pushed on the hose to get at other parts. Thus, that was a more pricy hose; another had to come from Germany part.

MP4.2+6.0

Notice on the side by side of new vs. old how the old one is just slightly shorter and that bellows stuff is a bit more compressed. Hard to picture all of it, but every way I turned it to compare, it seemed just slightly off. Wasn't sure until I put it in it would now mate up right, but sure enough. See second picture.

Part # on my old one coming out BTW was stamped 4E0 129 628G, which I used to order it. AudiUSAParts.com said it was superseded to the "M' suffix.

Bangerla

My waterpump had a slight drip for a few weeks, then catastrophic failure. The bearings went, and the pulley started to hit the engine, made a pretty terrible noise. The waterpump wasnt as difficult to change as I had anticipated. In hindsight you could probably do it without pulling the front. I only loosened the front end, and pulled it forward about an inch.

MP4.2+6.0

Seems like hardest part w/ clip in place is getting at the tensioner to remove and install serp. belt.

When I was under there last time I tried it with a big socket on a breaker bar and it seemed like I could get the necessary amount of movement to pull the belt and also get a good grip/position on the bar end--after I loosen the pulley bolts on the pump shaft face that is.

It seemed like the better tensioner access was from underneath, rather than from up top like I first thought, at least w/ the intake still in place. From on top I can't really get a breaker bar in there w/ a socket on it, and a box end wrench even in the right large size doesn't seem to reach down enough to make it practical to turn it. Any practical experience on this?

Bangerla

If I remember correctly, I think I used a socket wrench from beneath to release the tensioner. Using a strap wrench, you can loosen the bolt for the pulley and take it off of the pump while it is in the car. The bolts that hold the pump in are star bolts, so they can be a bit difficult as well, you have to be careful not to strip the heads. I partially stripped the head on the bottom bolt, which is the hardest to get to.