2000 A6 4.2 - Project Mayhem

[m_haiser]

but is the diameter the same? that could throw things off quite a bit

[v8a6]

but is the diameter the same? that could throw things off quite a bit

Yes, that is what I have to find out. I have contacted Max from 034 about the issue. I think if anyone will know, it will be him.

[m_haiser]

i wouldnt think machining the heads would throw anything off this far, unless you had done it repeatedly..... but if just the one cam is off then adj. gear would solve the issue

[v8a6]

I know one of the heads had a slight gouge in it. Maybe the shop had to machine them more than normal to get it out. Or, it could be, that they did it to raise the compression a bit.

[m_haiser]

what a hassle for what was supposed to pretty much be some bolt on and tune goodness

[v8a6]

what a hassle for what was supposed to pretty much be some bolt on and tune goodness

LOL. I know. I am laughing and banging my head against the wall at the same time.

[m_haiser]

well. im in it until you win it. keep the updates comin!

[v8a6]

well. im in it until you win it. keep the updates comin!

Hahaha... Good to know!

[v8a6]

One more thing, that could be contributing. The S8 heads had an extra small pulley on them. It was removed because the 4.2 heads, and belt routing, were different. S8 also has an underdrive pulley for the accessories, so using an S8 belt was not an option. I still think that the resurfacing is what is throwing things out. Just have to see if we can make an adjustable 1.8t cam gear work. These ones look purdy :)

[m_haiser]

any word back from max yet?

[v8a6]

Nope. But ddillenger wrote me this (he still can't post in the thread for some reason):

Anywho, you don't need adjustable cam gears. That's only required if they are splined, or keyed. The cam sprockets can go on anyway you want as they are just taper fit and held on with bolts. Simple stuff. Just pop the gears loose, and rotate the pulleys a few degrees. Tighten it all up, start it and check the readings. Re-adjust as needed.

I thought the 4.2 ones were keyed, but it sounds like they are just tapered, and can be infinitely adjusted. I am guessing Max will write back and say the same thing. SO, I am back to having someone take the front of the car off again and set the timing correctly. Why can't things just work right the first time?????????????????????????????? I'm going to have to find someone in Toronto who understands what is wrong, and can fix it. You wouldn't think that would be so hard, but I dont want to pay to have the front end taken off for the THIRD time and end up with the same problem.

Thanks ddillenger!!!

[m_haiser]

I dont see how they are infinitely adjustable, that would leave too much room for error which we know Audi would never do

[v8a6]

ddillenger writes:

If they were keyed you'd never get the tension uniform between all 3 sprockets. That's why the cam lock bar is needed, to hold the cams but allow the sprockets to spin, properly tensioning the belt.

[v8a6]

OK. I am finally starting to understand this whole thing with the timing. It sounds like the cam locking tool should guarantee that the two cams are lined up. However, a shop I talked to wrote this:

If the head has been machined or does not have exact same height as original head then no matter what you do the timing will be still off.

He didnt give further explanation, and I am still waiting to hear back from him with more details. Is he saying this because when the heads are resurfaced, bringing them closer together, then the cam locking tool will not fit properly anymore, because the pins on the bar dont line up correctly with the holes?
If so, would something like the locking tool below work (from Metalnerd), if it were modified (redrilled) for the slightly narrower space that the resurfaced heads create?

[v8a6]

Interesting video on the 4.2 timing belt change by Bob D
http://www.youtube.com/watch?v=MniODl1kLYA

[alterdcreations]

Do you know how much the heads were milled?

[v8a6]

Do you know how much the heads were milled?

Unfortunately, I do not. I don't think the shop that did the work would know either, by now. It has been almost a year since I picked them up.

[v8a6]

This is when I got them




This is after the p&p job

Outside chambers




Middle two

[v8a6]

OK. Nix the 'resurfaced heads causing the problem' idea. According to ddillenger, resurfacing the heads wouldnt be enough to cause an issue.

Right now, the number one suspected root cause is THE CAM SPROCKETS WERE NOT PULLED AND ALLOWED TO FREE SPIN WHEN THE JOB WAS DONE. The shop insisted that this was done, but it is the only thing that makes sense that could continue to cause this issue if the cam locking tool was used. Ill have to try another shop and see if this is the case.

[ddillenger]

I don't know of any machine shop that would remove enough material from a head to prevent properly timing the engine. If they required that much milling, you would have been told to find new heads. I'm not saying there isn't an effect, but it's negligible. Assuming all the timing components are the same between the s8 and a6 engines, the only other possibility is that the sprockets weren't popped loose prior to tensioning the belt. Those numbers are right in line with what you'd expect to see when the belt change interval is up.

Your cam timing will be about 1 degree off (retarded) per .040 removed from the head. In order to be 9 degrees off we're talking removing a LOT of material. Too much to be plausible.

[v8a6]

I don't know of any machine shop that would remove enough material from a head to prevent properly timing the engine. If they required that much milling, you would have been told to find new heads. I'm not saying there isn't an effect, but it's negligible. Assuming all the timing components are the same between the s8 and a6 engines, the only other possibility is that the sprockets weren't popped loose prior to tensioning the belt. Those numbers are right in line with what you'd expect to see when the belt change interval is up.

Your cam timing will be about 1 degree off (retarded) per .040 removed from the head. In order to be 9 degrees off we're talking removing a LOT of material. Too much to be plausible.

Thanks for the info. I think that rules out the head resurfacing issue.

[alterdcreations]

I don't know of any machine shop that would remove enough material from a head to prevent properly timing the engine. If they required that much milling, you would have been told to find new heads. I'm not saying there isn't an effect, but it's negligible. Assuming all the timing components are the same between the s8 and a6 engines, the only other possibility is that the sprockets weren't popped loose prior to tensioning the belt. Those numbers are right in line with what you'd expect to see when the belt change interval is up.

Your cam timing will be about 1 degree off (retarded) per .040 removed from the head. In order to be 9 degrees off we're talking removing a LOT of material. Too much to be plausible.

I noticed that as well, i milled heads up to .065" and didn't have a problem with timing.

I'm thinking that it might be off one crank gear tooth. Did they use the Audi locking tool or set the motor to tdc using cylinder #5?

Is their another shop around

[v8a6]

I noticed that as well, i milled heads up to .065" and didn't have a problem with timing.

I'm thinking that it might be off one crank gear tooth. Did they use the Audi locking tool or set the motor to tdc using cylinder #5?

Is their another shop around

I think they tried to set it both ways. The thing is, if you dont pull the cam gear sprockets, and let them free-spin when you are tensioning the belt, then the two banks are not guaranteed to be timed correctly. You may be able to get one side timed right, but then the other will be out. Lock the cams in the correct position using the bar, and then tighten the sprockets in place once the belt is on and tensioned. This is the 2.7t, but you get the point.

[v8a6]

Oh yeah, lots of shops in the Toronto area. I just have to find one that will do the job properly, at a reasonable price.

[m_haiser]

if you get another shop to rectify the issue and it was timed incorrectly i would demand a refund from previous shop on the grounds that theyre obviously disfunctional

[v8a6]

Yeah, I guess I will cross that bridge when I come to it. I don't want to start blaming anyone for the problem, until we figure out exactly what it is. If it does turn out to be something as simple as the cam gears were not loosened, then I will be pretty angry. I have spent many, many hours, and quite a bit of money trying to figure out the problem, and would have never found it if Alterdcreations didnt suggest checking the timing. And again, if I didnt have a genuine Vagcom cable, I would have never found it.

Next Steps
Get the timing done FOR THE THIRD TIME. This time, by a different shop. Make sure that they understand that the cam gears have to be loose when tensioning the belt.
See what VCDS block 093 says. I really can't see how it wouldnt be dead on, if the lock bar is used and the gears are loosened during the procedure. The pieces on the cams that attach to the lock bar are keyed to the cams. So, if the lock bar if put on properly, the cams really have no choice but to be perfectly timed.
If VCDS still shows them being out, then it will have to be something else. Unlikely, but these are the other options:
bad cam position sensor(s)
VCDS reading incorrectly
LWFW tone ring leading to incorrect reading
Slipping cam sprocket(s)
Cams or keyed piece on end of cam is messed up badly, and no longer align exactly at zero

I think all of these options are very unlikely. But, they would be the next things I would look into if the next guy comes up with the same results.

[Widebody4.2]

Could the cams have gotten mixed up?
Don't the s8 use a different rocker?
Where the proper rockers used?

My current questions

[v8a6]

IIRC, all four cams are different, and i dont think the car would run if they were not in the correct head caasting.

The entire S8 heads were used, including rockers, valve springs, cams, and lifters, which are all different than the 4.2 ones.

[m_haiser]

im practically banging my head in frustration for you!

[Scotty@Advanced]

Count the number of links on the cam chains. Also verify the cam chain sprockets are oriented correctly. It's nearly impossible to mill a head so much that the timing is affected.

The exhuast cams are driven by the timing belt and the intake cams are driven by the chain.. Which also has the cam sensor on it, so if the exhaust cam timing is correct, then the issue is with the intake cam, the intake cam adjuster or the chain.

[v8a6]

Count the number of links on the cam chains. Also verify the cam chain sprockets are oriented correctly. It's nearly impossible to mill a head so much that the timing is affected.

The exhuast cams are driven by the timing belt and the intake cams are driven by the chain.. Which also has the cam sensor on it, so if the exhaust cam timing is correct, then the issue is with the intake cam, the intake cam adjuster or the chain.

091 and 092 are pretty much dead on, so I dont think there is a problem with the exhaust to intake cam timing. It is one bank on 093, which I believe means one exhaust cam is out of time with the crankshaft. Im following up with a couple local shops to see what they can do. I am guessing the cam gear on the one head is out half a tooth or so, because of the different routing on the S8 belt (extra roller, underdrive pulley). From what I understand, the proper way is to pop the sprockets and let them free spin when doing the job. However, I think a lot of shops are probably skipping this step. Below is a video of a Audi V6 timing belt change, and I didnt see them pop the gears.

Maybe if they were perfectly aligned in the first place, everything would be OK. But that is obviously not the case with mine.

[v8a6]

Tool used to pop the sprockets


or with a 2-arm puller

[ddillenger]

I never use a tool. Just loosen the bolts 2 turns and smack them (the bolts that is) with a hammer. Pop right off and eliminate the chance of damaging the cam sprocket.

That, and the cam lock bar isn't required if you pull the vc's. (flame away)

[v8a6]

I never use a tool. Just loosen the bolts 2 turns and smack them (the bolts that is) with a hammer. Pop right off and eliminate the chance of damaging the cam sprocket.

That, and the cam lock bar isn't required if you pull the vc's. (flame away)

Good tip.

I don't really care if they use the cam lock tool or set it manually, as long as the sprockets are popped. I think that is where the problem lies.

[alterdcreations]

I would listen to Scotty. Double check everything because as we can tell the current shop wasn't up to the task. maybe take it back and tell them how to do it.
Might be just the right time to get hands on!

[v8a6]

That is exactly what they checked the second time around. They pulled the VCs and counted the links on the chain. They even pulled one of the cams, because they thought the chain was wrong when it only had 15 links. Then, they found that is how it is supposed to be. When I got the car back, 091 and 092 are near perfect at idle. They used to sit at -1, and dip to -2. Now, they sit at 0, and dip to -1 every once and awhile. So, I really think the chain on the inside of the head is lined up properly, unless I am really misunderstanding how all this works, and what 091 and 092 represent.

[v8a6]

Might be just the right time to get hands on!

You made a lot of sense up until that statement LOL! My technical abilities under the hood are severely lacking.

[Scotty@Advanced]

From what I understand, the proper way is to pop the sprockets and let them free spin when doing the job. However, I think a lot of shops are probably skipping this step.

You can't get a good time without loosening the cam gears and following the factory belt tensioning sequence.

[A62TURBO]

I think using the cam bar is very important for keeping the cams lined up with the sprockets off. The bar and crank pin were very useful imo, this is how I kept things lined up.

[alterdcreations]

I hope you get the timing figured out....At least It would be nice to eliminate the know problem and go from there.
might be as simple as the shop not pre-tensioning the belt between the cam gears , and allowing the hydraulic tensioner to take up slack....
hope the new shop will let you watch