How does the camshaft adjuster work? Think I broke mine and looking for help ....

[SFJ_RS6]

Well, yesterday I was making steady (though slow) progress on my engine-out maintenance work. Today, I'm looking for help to figure out what I broke.

Here's the story: As I was changing the timing belt, the driver's side cam shaft rotated on me. With the crankshaft locked, I had a puller on the LH cam pulley. When the pulley popped off the taper it must have jarred the camshaft, allowing it to rotate clockwise out of position. The big hole in the camshaft end plate moved from the 9 o'clock TDC position to about 11 o'clock. (My dumb fault - I should have had the cam holder bar in place while removing the pulleys.)

I put the camshaft back into position and finished installing the timing belt, hoping for the best. But I was not lucky. Now when I turn the crankshaft (clockwise) I get loud clicks/clunks from the front of the LH drivers side cylinder head. With the valve cover off, as I turn the crankshaft I see the intake cam chain go very slack as each of the intake cam lobes starts to open its valves. Once the valves are just past fully open, the force of the valve springs pushes on the passing lobe, forcing the camshaft to rotate suddenly. This sudden rotation takes up the slack in the cam chain with a jerk and causes the clunk. I can see the cam tensioner move up during rotation, allowing the slack in the cam chain.

I'm not quite sure how the cam adjustor is supposed to work, but from what I see and hear I think I need a new one.

So, I'm looking for help to try and confirm this before spending $$$. I'd like to understand how the cam rotating during pulley removal could have caused the cam adjuster to fail. Does anyone know how it's designed and works? What creates the pressure for the tensioner? Are there hydraulics involved for which a seal failed? What does the solenoid do, perhaps valve oil pressure to adjust the tensioner during operation? What causes the tensioner to move up and down when the oil is drained and I am just rotating the crank by hand?

If you can provide any help or have other ideas about all this, I'd greatly appreciate it!

Steve

[ttboost]

Probably not possible to be off only a few teeth and the valves are hitting pistons?

[SteveKen]

BTDT. This is normal.

You should be able to start it up and everything will be fine.

[kevin]

They tend to make a little noise when the oil drains from them. First thing to do is turn the engine over by hand, clockwise and bring the crank damper up on TDC, with the cams in the right cycle. Then look for the notches on the cam gears, they should be lined up with the arrows on the first camshaft bearing caps. I don't think it's possible for the chain to jump a tooth when both cams are in place.

[kday]

I should have had the cam holder bar in place while removing the pulleys.

I don't think this is actually possible with the Audi tools. The Bentley specifically shows the bar not in place when the pulley is broken free. I tried to do it with the bar in place but couldn't get good purchase on the pulley.

I didn't notice any noise in my case, but maybe your engine has been without oil pressure for longer?

[SFJ_RS6]

BTDT. This is normal.

You should be able to start it up and everything will be fine.

Thanks for your response. I'm starting to think maybe things aren't are bad as I thought. Just to clarify, it sounds like the cam adjuster is pressurized by engine oil, and when I start the engine and have oil pressure the adjuster will pump-up and operate normally?

[SFJ_RS6]

They tend to make a little noise when the oil drains from them. First thing to do is turn the engine over by hand, clockwise and bring the crank damper up on TDC, with the cams in the right cycle. Then look for the notches on the cam gears, they should be lined up with the arrows on the first camshaft bearing caps. I don't think it's possible for the chain to jump a tooth when both cams are in place.

Thanks Kevin. I have just checked this and the notches on the cam gears do line up with the arrows on the bearing caps. Also, there are 15 chain rollers between the arrows as spec'ed in Bentley. So it looks like the chain has not jumped a tooth, which is very good news. I think I'll go with the theory that the oil has drained from the adjuster and things will recover to normal when I have oil pressure.

Steve

[SFJ_RS6]

I don't think this is actually possible with the Audi tools. The Bentley specifically shows the bar not in place when the pulley is broken free. I tried to do it with the bar in place but couldn't get good purchase on the pulley.

I didn't notice any noise in my case, but maybe your engine has been without oil pressure for longer?

Thanks kday. You're probably right about the tool incompatibility - I'll check it out. I used the Audi T40005 cam lock bar with a 2-jar PosiLock puller, since I don't have the Audi T40001 puller set. I'll see if I can use my cam bar and PosiLock together. I saw that same picture in Bentley, so you're probably right. I remember a picture from one of your recent threads where it looked like you used some locking pliers on the puller to prevent rotation, which is a good idea that I'll try.

My slow approach to this project has meant that its been without oil pressure for several weeks. Interestingly, when I turn the crank this morning, I can also hear a slight click from the other cylinder bank (passenger side), and that cam shaft did not move when the pulley was removed. I hope this adds evidence to the theory that the chain slack and noise result from oil drain down instead of damage to the cam adjuster.

Steve

[Elevens]

I think you'll be fine SFJ, I just did the Wife's 2.7 a few months ago and so long as all of you Cam timing marks along with the Crank timing marks all align up correctly at the same time there should be no issues. The cam chain will make some noise upon startup, I know mine scared the shit out of me when I initially started up. But then as the Oil pressure built up the chain noise went away as the tensioner tensioned the chain. Good luck with the Project............................

[SFJ_RS6]

Thanks Elevens! I sure hope it turns out OK. And thanks for sharing that info about your 2.7 experience. I just went through the exercise of turning the crank and watching the intake and exhaust cams relative to #5 cylinder which was locked at TDC. With the cam moving from 9 o'clock to 11 o'clock, neither the intake nor exhaust valves would have been forced open onto the #5 piston. So now it's just a matter of whether the tensioner will pump up when I start the engine...

Keep thinking those positive thoughts!

Steve

[mdegracia]

I definitely had a few sleepless nights when I did my Tbelt during my motor pull. I had a similar thing happen, basically went through and reset everything and reiterated the process two more times! No problems at start up.

The chain adjusters are loud and clunky when rotating by hand, especially when the motor sits for awhile.

[vtraudt]

Different engine (2.8 ATQ), similar concern:
Previous owner found plastic in oil pan. Audi shop said needed new cam chain tensioner.
Car runs crappy.
Tons of misfires bank 1 (passenger) cyl 1-3.
VAGcom block 90-93 show 34 degree bank 1, -3 degree bank 2
Phase (block 93): zero and zero.
crank on TDC mark and cam lock tool installed (timing belt timing ok)
Valve covers removed, no damage visibile to cam chain tensioner/guide (obviously, only top visible).

Any suggestions?

If I remove the cam tensioneres (and remove cams), how can I test them (too expansive for 'trial and error replace parts')?

[G2]

Typically broken or excessively worn chain guides are a tip of the iceberg situation with other issues at hand-- mostly engine wear-- from, in personal experience of seeing more than a few tired engines lose their guide rails. A small mirror may allow viewing the bottom guide.

The disparity between cam angles suggests either massive guide rail material loss (retards timing), clogged intake screen, or a failed selenoid valve (cross check R values; 15K?). Check # of links between reference points (16 or 17 if memory serves me).

Typically the cams should be advanced at lower revs:
Apply power and ground, check for actuation? Also check supply from DME for power/ground, lose or broken wires.

For a sunday and with BIH (beer in hand) that's all I can fathom for now......

[vtraudt]

Typically broken or excessively worn chain guides are a tip of the iceberg situation with other issues at hand-- mostly engine wear-- from, in personal experience of seeing more than a few tired engines lose their guide rails. A small mirror may allow viewing the bottom guide.

The disparity between cam angles suggests either massive guide rail material loss (retards timing), clogged intake screen, or a failed selenoid valve (cross check R values; 15K?). Check # of links between reference points (16 or 17 if memory serves me).

Typically the cams should be advanced at lower revs:
Apply power and ground, check for actuation? Also check supply from DME for power/ground, lose or broken wires.

For a sunday and with BIH (beer in hand) that's all I can fathom for now......

G2, thanks a bundle. I had a chipped of piece of the guide on a (well maintained, healthy, 100k miles) 2000 A4 1.8T once. So hopefully NOT the tip of an iceberg here.

a) I will try a peak 'down there' to see bottom. With 34 degree on bank 1, and tons of misfires on bank 1 (passenger side), I concentrate on bank 1. Right?

b) R value check: across the (haven checked: 2?) pins of the connector? Easy enough, will do both sides.

c) Chain link check. Will just count links between same ref points on both sides.

a) - c) hopefully later this morning and report back with results.

I found complete sets (2 tensioners, gaskets, etc.) for $570 or on blauparts. Are similar 'sets' available for one bank only? Good sources? (preparing for potential need for new tensioner).

[vtraudt]

Apply power and ground, check for actuation?

Polarity important? If so: which is ground?
Power is battery power (12.7V) or ECU power (5V)?

Read that the adjuster/tensioner most often fails due to mechanical (jammed) failure?

Since the angles 34/-3 never seem to change (and 'adjuster: off' showing in VAGcom): electrical malfunction?

[vtraudt]

First results:
driver side (bank 2) resistance across both pins off cam tensioner/adjuster: 14.2 Ohm
ditto passenger side (bank 1): 13.9 Ohm

Note: OHM, not kOhm!
What is 'inside' the adjuster? an electric motor? Otherwise, that would be a fairly low resistance (and drawing high amps).

Obviously, was hoping for big difference. Not so.