3.0 timing question

[19jdog]

When doing the timing belt the Bentley call for a t40028 tool to set the camshaft.

"insert T40028 socket at camshaft adjuster for exhaust camshaft on left cylinder bank. Turn rotor of camshaft adjuster clockwise to 10nm or 7lbs up to stop"



What does this mean? I already have the camshaft locks on. Can't I just install the belt, set the tension and continue putting her back together?

[SJorge3442]

First off. Check out those clean heads! That tool helps set the preload on the exhaust cams. Many contemplate if this is needed. When I did my TB twice, I believe the tool never did anything. The cams were already locked down, as I would expect them to be. Since you had everything apart, I'm unsure if it would make a difference. Did the JHM tool rental only come with the locks and not the cam socket?

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[19jdog]

First off. Check out those clean heads! That tool helps set the preload on the exhaust cams. Many contemplate if this is needed. When I did my TB twice, I believe the tool never did anything. The cams were already locked down, as I would expect them to be. Since you had everything apart, I'm unsure if it would make a difference. Did the JHM tool rental only come with the locks and not the cam socket?

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Yep, the jhm kit only came with the locks. Dang, guess I'll continue and see what happens.

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[john_gonzo]

Check out the paragraph that starts "This is easy to do, but confusing without having done it...." in Post 14 of Crank-Seal-Replacement_3-0L-AVK-Oil-Leak-Madness.

[csosnowski]

t40028 engages the cam adjuster rotor and sets it in the locked zero position. On startup, oil pressure is applied and the adjuster is then unlocked. It is impossible to properly set the base timing for the 3.0 AVK engine without locking the exhaust adjusters at zero before setting the initial belt preload.

Most people don't feel the thing lock, it is important to at least attempt get it to lock, use needle nose pliers, big tweezers, snap ring pliers, whatever. Make an effort to zero those cam adjusters or the car will never run correctly.

[19jdog]

t40028 engages the cam adjuster rotor and sets it in the locked zero position. On startup, oil pressure is applied and the adjuster is then unlocked. It is impossible to properly set the base timing for the 3.0 AVK engine without locking the exhaust adjusters at zero before setting the initial belt preload.

Most people don't feel the thing lock, it is important to at least attempt get it to lock, use needle nose pliers, big tweezers, snap ring pliers, whatever. Make an effort to zero those cam adjusters or the car will never run correctly.

Yep yep! I used needle nose pliers. It locked

[csosnowski]

Yep yep! I used needle nose pliers. It locked

Excellent! Great work!

[SJorge3442]

So I still don't understand what happens here. If that cam locks are in, what are we rotating? I've used this tool both times I've had my timing belt off, but whatever it does, is still a mystery to me.

[cschuster]

So I still don't understand what happens here. If that cam locks are in, what are we rotating? I've used this tool both times I've had my timing belt off, but whatever it does, is still a mystery to me.

It's resetting the cam adjuster position back to 0

[deyrag]

When i did mine i never touched that part. I did not even pop off the cam seal covers as they were not leaking and I was not going to break the cam drive bolts loose. i put the crank pin in, locked both cams and replaced and tensioned the belt.

Has been running fine ever since so either (A) I should have done this step and got lucky or (B) I could have done it but it was not really needed as everything was in the correct position. I am assuming (B) seeing as i never broke the bolts free to allow the cam drive gear to spin on the shaft.

[SJorge3442]

When i did mine i never touched that part. I did not even pop off the cam seal covers as they were not leaking and I was not going to break the cam drive bolts loose. i put the crank pin in, locked both cams and replaced and tensioned the belt.

Has been running fine ever since so either (A) I should have done this step and got lucky or (B) I could have done it but it was not really needed as everything was in the correct position. I am assuming (B) seeing as i never broke the bolts free to allow the cam drive gear to spin on the shaft.

I'm confused as to how you tensioned the belt if the cam gears weren't loose . When the cam gears are loose and you tension the belt according the bentley, the cam gears spin and the tension of the belt between the gears increasing dramatically. Without the gears unlocked, this wont ever occur. I'm really confused as to how this worked for you.

[deyrag]

Maybe I just got lucky but it all worked out ok. There was no slack in the belt before I released the cam locks.

[walky_talky20]

The 'rotate with the special tool' thing is to lock the variable camshaft advance mechanism back to it's zero point. It is probably supposed to do this on shut down, but when you are retiming the engine, you best be sure things are locked in.

The 'breaking loose of the cam gears' thing is to ensure precise timing, given such a long belt. Without breaking them loose, the accuracy is based only on the number of teeth between things. With 4 variable cams, and a very long timing belt, Audi feels that there is not enough accuracy. As such, they have used a timing method whereby the cam gears are infinitely adjustable. Everything can theoretically be dialed in with a fair amount of precision.

The way that deyrag replaced his belt mimics that of a convential V6 timing belt job (like on say, a Hyundai or Toyota). He used the cam and crank locks to merely hold things still while he swapped the belt out "tooth for tooth". The variance between the 2 belts is never adjusted for. Nothing is dialed in, nothing is changed. It all stays the same. This is generally good enough (and is certainly good enough for Toyota and Hyundai). However, with 4 continuously variable camshafts (and software by Audi), the 3.0 tends to be pretty picky. This 'cheater' t-belt method sometimes works out ok. And sometimes can result in timing that is off just enough to cause a VVT fault code.

The real test is to pull up Measuring blocks 090-093 in VCDS after you're done. This will show you how close you got to 'perfect'. There is a specification in the Bentley manual for what is considered satisfactory.

[t64030]

Maybe this is why my timing is slightly off and I can't rev above 5k. About time for another timing belt kit any ways, I'm going to order one and do it correctly in a week or two.


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