Bryce Kaufman

I'm puttering along in my 2002 A6 4.2l v8 (Nicknamed "Moneypit", three guesses why) when suddenly a wild check engine light appears. Engine seems to be running fine, so I make my way home and pull the code: P0012: Camshaft Position “A” - Timing Over-Retarded (Bank 1). Ran it twice more to confirm the code. First trip to work did not trigger code, second did. Garaged the vehicle after that.

So I do my research and find that I almost certainly have an issue with the control valve/solenoid for the camshaft tensioner on the passenger side. However, all the pictures and guides I find are for a C6 chassis, leading me to go in thinking the solenoid and valve are a single part and I should be able to pull it out, blow it out like an old games cartridge, and plug it back in.
But this is a C5, and it's two separate parts. It's a solenoid, which appears to be fully functional, and a piston, which has a destroyed O-ring. No visible blockages. Tada, source of problem found. Cleaned up the piston, blew the rest of the o-ring remains out of the bore it fits into.

.....But I cannot for the life of me seem to locate a replacement O-ring, specs on said O-ring, or anything online admitting the thing exists. All parts places I've looked at only list the ENTIRE TENSIONER as an option for purchase. I simply cannot justify spending $200-$700 when all I actually need is the silly O-ring. Even if I have to buy a pack of 100, that's <$20 with shipping. I just need the size and material specs. Pads on the tensioner looked fine when I changed a leaky valve cover gasket ~8,000 miles ago. I have a high degree of confidence it's just this seal. Only possible chain rattle noise I've heard is the normal startup noise these things tend to make that goes away and stays away after ~0.5 second.


I have a Bentley service manual but I think I got the wrong one because it's totally useless for engine related tasks other than pulling the valve covers. Those of you with the fancier more expensive books/erWin guides, or those that have attempted this before: What size/type of O-ring does this thing take? Does anyone know where I can get a "proper" part?

I know I should probably call the dealer or something but since the official audi parts site only lists the entire tensioner I'm real sure they're gonna say that's all they sell. That, and my local dealership is a giant pile of scam artists, charging usually no less than 20% more for parts than what parts.audiusa lists. A friggin KEY costs $300 at this place and that's before programming the immobilizer chip, but I digress.

Pictured is the valve piston and all I could recover of the original seal. If I can get inner/outer dimensions and whether it was square-section or round I should be able to make an easy fix here. I can measure the piston, but can't quite get the calipers into the bore to confirm it's diameter. It appears to be 9x10x1mm but would appreciate a second opinion.

BernieBenz

Ah come on, be resourceful!
You can measure the dia of the bottom of the O ring groove and the dia of the top of the groove's side lands. Guess at the clearance to the cylinder. Go to an O ring design manual and pick a suitable squeeze for the application. Select a common round section ring, Buna N material, Request a sample from an supplier and put it together. Your guessed dimensions appear to be wrong.

Harleyguy

Auto parts stores sometimes sell O-ring kits that have the raw material in various dimensions that you cut to the correct length then superglue the ends together to form the ring. By cutting the ends on a bias while they overlap a bit you get more contact area and they hold pretty well. Disassemble the other side and get the measurements on the correct ring. Solution #2...buy a new tensioner. They are about $850 per side from AutohausAz.com. Will be similar price at other after market sources. Solution #3.....get one from a scrap yard.

Bryce Kaufman

In case anyone was wondering, the reason I couldn't find specs for an O-ring is because there isn't one. Removed all debris from bore, re-assembled, no more code.

....Which is precisely why I asked if anyone with a better guide could try to look it up, because I wasn't sure if it had one in the first place.

Dr.Aronis

Make sure you check the pads on your cam tensioner. You can replace just the pads (available in a seal kit) and save the 700 each.

But if you let the cam tensioners go, you are screwed.

You cannot see the bottom pad without removing the dam thing! And you need to replace the 56 bolts which hold the cam shaft in when you pull this all apart.

My "warning" which my mechanic ignored was the fragments in the oil pan.

quattropowerA8

Fixed 5 second boot noise? I have the same problem but without error codes at the moment, it only makes noise for about 3 seconds when starting.