AVK 3.0 motor timing and failure modes..

[ninefingerz]

I recently acquired a 2002 Audi with the 3.0 motor in it. The car is absolutely immaculate inside and out. The owner said that the cam came apart on the drivers side, may have taken out the drivers side head or both.
For what I paid for it, I couldn't refuse the deal. What I know about it at this point is the exhaust VVT assembly on the drivers side did in fact grenade. The outer mounting ring (sits inside the gear that has 6 bolt holes in it) was sitting on the shock tower when I bought it. The good news about it is the car will still start. This tells me right off the bat that at least the passenger side bank is healthy. I have no idea how the gear stayed in place after the bolts sheared, but it did. So the passenger side timing is correct, drivers side intake is correct, and the drivers side exhaust is unknown. Considering that the drivers side timing cover was removed, the damage discovered, and the cover put back in place correctly, I assume that it was taken to a dealer or shop for assessment, and the estimate was ridiculous, as it usually is with these cars, and especially these motors. What I'm hoping for at this point is when the gear cut loose. On this 6cyl motor, the exhaust cam has lobes 120 degrees apart, which by pics and lobe geometry, there are 3 places the cam could have come to rest without causing valve damage. First I'm going to pull the valve cover. If there was severe valve contact, I will have lifters that aren't contacting the cam. If I have no gaps in the lifters, I will pull the exhaust manifold and 'gas check' the exhaust valves, meaning make sure the cam followers will spin freely by pushing by finger, and pouring a bit of fuel on top of each of the exhaust valves and look for leak down. And by leak-down, I mean if you pour in a cap-ful of fuel, and it dissappears as soon as I pour it, I'm in trouble, or at least have to get into the motor further. Timing wise, I have read a bunch of screaming about how this motor is timed, but I think it's actually pretty clever. Put the cam alignment tools on, set the crank at TDC, put the timing belt on (with all 4 camshaft bolts loose), tension the belt, set the VVT clockwise (in case it hadn't returned for some reason not under oil pressure) and torque the bolts to 75ft/lbs. I've built a bunch of motors over my lifetime, and I've had plenty of situations where you 'fudge' timing marks to make it work, or clock to get is as close as possible. Head gasket thickness, head dimension, block dimension all come in to play with 'correct' alignment. This method, albeit different, takes all of that out of play.

Any input or comments are appreciated, I've done a lot, but do not share as much as I should, so here's my attempt.

BTW, I'm just an owner. Not a shop, a flipper, etc. I've built every type of motor imaginable, from jet turbines to string trimmers.

[ninefingerz]

Well good news! I picked up a used pulley to replace the one that came apart, retimed the motor with the rest of the parts that were there and hand cranked the motor. I had a 30psi bump in each of the questionable cylinders, so no internal motor damage. When the bolts backed out of the pulley as it was coming apart, they ground into the block behind the pulley (VVT valve block.) The valve for the exhaust cam was pinned into the block due to impact forming that occurred. The crazy thing is I hopped on ebay, put in 'audi VVT' and the only thing that popped up was the exact valve block that I needed, and cheap too! The car only has 95,000 on it, and had the 80,000 mile service done on it, so I put a new timing belt on, cleaned everything up, reassembled, and it runs great!

[walky_talky20]

Wow. That's amazing. It is not often that you have a valve timing problem on an Audi and make it out without some bent valves. You lucked out with that, and with finding the VVT parts. I don't assume those come up very often in good used condition for a fair price. Nice work!

I'm wondering if you used the lock tools to time it? The 3.0's can be pretty fussy about the timing. Even with the tools there is even some variability. If you want to see how close you got everything, you can check in VCDS measuring blocks around 090-094 or so. That should give you the cam phase angle information. Ideally you want all 4 cams to be zero, but there is some acceptable margin.

[SJorge3442]

Wow. Good fix! I keep randomly coming across articles with people having issues with these damn cam bolts. You're talking about the ones on the front of the cams that hold the cam gear on, right? If so, I have heard of quite a few people who had these bolts back out on them and cause some serious damage. Having played with these bolts twice, I might go ahead, pull the valve covers, timing covers, and replace these bolts with new ones. I do believe they are TTY bolts, but no one ever talks about replacing them.