So it was time to do the second replacement of my timing belt on my 2005 A8 4.2 V8. Routine maintenance, nothing apparently wrong. I got the belt, new pump, pulleys, etc - the whole kit and proceeded to strip the car, putting it into service position, taking photos of everything that i took off along with notes, bagging and tagging along the way. everything was going great.

The previous timing belt was put on by Audi at around 80k miles. one thing that i did notice when i took the old belt off is that the eccentric pulley was on in the tightest position possible, and the piston applying force on the pulley tensioner was fully retracted - the belt was tight. I have the correct tool to lock the cams together in timing. I proceeded to put on the new belt - but putting it on following specifications so that there is 5mm of piston on the pulley tensioner and the correct torque. all seemed well.

I then went to slowly hand crank through two revs of the crank - i got nearly half a crank through and came to a stop. I was able to reverse back to TDC and go back nearly half a revolution. so in total - i can get about 95% of the way through a revolution.

The first thought is - it must be out of timing. I know i need to revs of the crank to know for certain by that method and i cant get that far. so i remove cam case covers to watch cams and valves, i make and mark a dipstick for TDC and BDC. when it stops there is a piston on each bank a few MM off TDC, on the drivers side it is in compression stroke - valves are closed. on the passenger side - it is just completing exhaust stroke. The cylinder adjacent on the same cam just cleared exhaust stroke.

To further trouble shoot i advance, the retard the crank timing a tooth off TDC to see if it would stop the crank in a different position - but the crank stops in same position (i am not using brute strength - when it stops so do i - using a ratchet - so if interference it would not damage)

I have also been using a borescope through the spark plug hole - the valves on the cylinder in compression stroke appear seated. the other cylinder does not appear to have piston and exhaust valves interfering.

For ****s and giggles i took the lower and upper oil pan off to see if there was anything interfering with the connecting rods and crank - dont see anything.

I am lost for words now. Am i overlooking something here on the timing? Could a faulty starter or torque converter or anything else cause this symptom too? What else should i diagnose? I am probably missing part of my diagnosis - i have been troubleshooting different things on this!

Thanks!
Wes

 

DUDE!!! I literally fought this battle 3 weeks ago. I was having to change out the chain tensioner on the passenger side. Decided to do both sides. I got everything changed out and went to turn the engine over by hand and it actually rotated fine, no issues. I had gone slightly past TDC and the cam lock bar didn't want to slip on like it should. So I started to turn is another 2 rotations (slowing down on the 2nd) and got about 3/4 of the way through and bam... It stopped on me.

While there was much cursing and head scratching, I pulled everything back apart. No cams in the engine do NONE of the valves were open. Same thing. Damned thing would not turn over, even going backwards, without hitting something. To make a long story short, it turned out to be some carbon on the valves, intake, or even on the piston tops that had fallen down into a couple of cylinders somehow. I poured all of the cylinders full of mineral spirits and some SeaFoam cleaner and let it sit over night. Filling the cylinders full to the tops of the spark plug tubes confirmed that there were no bent valves because none of the fluid leaked down over night. You will have to reset the tension on the timing belt if you turn it backward. It really doesn't like going backward with the belt and cams in it.

I pumped the fluid back out with a little hand pump and go to turning the engine over. I got to the tight spot and started rocking it back and forth. Some fluid shot out of the spark plug holes (be sure to place some rags off the holes as not to shoot the fluid all over the engine bay) and it started to turn over. Hit another spot about halfway around and repeated the rocking, letting the fluid help break down the carbon chunk. Finally got it all freed up and reassembled. It really doesn't take but just a tiny amount of material to prevent you from turning the engine over by hand. Even with a 24" 1/2 drive breaker bar..

If you do this, be sure to put some oil down in the cylinders and turn it over by hand a few more times to re-lube the cylinder walls. Also be sure to spin the engine over a few times, still with the spark plugs out, with the starter to expel as much oil/fluid as you can to prevent a hydraulic lock when restarting. You may have to spin it over several times with the throttle to the floor to get it to start. It'll smoke like hell for a couple of minutes to before all the excess oil and fluids will burn out of the cylinders.

You can read a little more about it here: https://www.audiforums.com/forum/aud...-issue-222007/

 

I will give that a try over the weekend. Super frustrating that it won't get past a point in the revolution! I will let you know how it turns out. Thanks.

 

Just read your cam tensioner post - know that feeling. I know the tensioners popping up and down without oil pressure - been watching them on the A8 now for a while. I had the V6 in an A6 before and the cam tensioner went on it too - had to fish the plastic out of the engine.

 

At first, I thought a chunk of the plastic tensioner pad had fallen down and somehow made it way to where it had gotten wedged between the crank and something in the bottom end. Took the pan off, which really needed to be done anyway, and cleaned all the pieces out of the pan and oil pump screen. Also inspected for metal shavings and really didn't see anything out of the ordinary for an engine with 215K miles on it.

The popping up and down of the tensioners is bit unnerving at first. I was like, WTF?!! LOL Oh well, it all worked out and the thing is running like a top now. The only other thing that I found unusual was the non-keyed timing belt gears on the cams, just a tapered fit that is held together (quite well it seems) by the long bolts. I guess that does allow for a more precise initial timing setup on such a long timing belt.

 

I owe you a pint! left the Seafoam in over night and the car turns over by hand.... got it turning over about 6 times... could not believe it. one cylinder was caked with Carbon!

Thanks a million for sharing your experience!
Wes

 

Yep.. I was SO relieved that's what it was too... My Dad talked me out of ripping the heads off and trying it. Glad you got her back on the road to running again. Again, be sure to put some oil (just a couple of ounces) in the cylinders and turn it over a few times by hand to get a good film of oil back on the cylinder walls. Spin it over with the starter before putting the plugs and coils back on just to make sure there is no excess oil in the cylinders that can make it hydraulic lock on you when actually go to start it. No lube for the rings will wipe them and it'll start smoking all the time. These PCV engines are just horrible for carbon build-up internally in the intake and tops of the pistons due to having to burn that crappy oil-vapor. Running Sea Foam in the oil and gas will help but my intake had a pool of oil in the bottom of it when I took it off and turned it over to clean it...

 

So how long did yours blow smoke for after the Seafoam and then oil in the cylinders, Wow was there a lot of smoke at first.

have it going for a few hours now,and when i rev it.... i think i get every mosquito for half a mile. this is a picture of the first startup. it is not this bad now - but still a little smoke coming out and i just wondering how long it took you because i need to get it inspected.

Thanks!

 

Mine cleared up after running about 10 minutes. Yeah, it did look like that at first. LOL Just drive it a few days, it'll be fine.