2009 MCS. Had it in for HP fuel pump replacement and the dealer found a crack in the valve cover. They recommend:
1. New valve cover
2. Check timing - because valve cover cracked
3. Carbon cleaning - 3 part complete

Called to find out how the timing is impacted by a cracked valve cover. Was told that the Vanos will compensate for air that is leaking into the crack (agreed) but that if it has to compensate long enough and hard enough the Vanos timing will mechanically change and needs to be checked and adjusted. This is where he lost me. The price for that is $125 so it sounds like an hour labor.

How can valve timing mechanically drift or change because of leak compensation? Just doesn't seem plausible to me, any ideas out there?

 

I don't know if this answers the question you are asking, but I had a timing issue that went on for a long time. Finally replaced all of the timing chain components and the VANOS solenoids.

That did not fix the timing issue.

Finally stripped the entire VANOS system down and found the inlet VANOS gear had compensated so long and to such a degree that the internal spring broke. It had to be replaced, and then the car had to be driven over 200 miles to "relearn" the timing.

Finally fixed my issues.

That may be what they are referring to - although the gear itself is almost $500 so maybe they are just adjusting it?

 

The car uses an adaptive ECU, so the tables are constantly learning and changing. The VANOS Solenoid is simply that; a solenoid.

If the tech is worth his salt he would put the computer on it and do a VANOS solenoid test, which actuates the solenoid to varying degrees of adjustment while running. If it passes then what reason do they have for telling you to spend money?

Any time you fix anything engine related on these cars it is smart to reset the adaptations.

If the solenoid were to "drift" you would get a timing over retarded or advanced code accompanied with possible misfires and poor performance. Are either of these present?

 

If I understand the system correctly the ECU in compensating for an air leak pushes the Vanos solenoids farther and more frequently. I can understand a reset on the ECU to go back to a default mode. Was the service advisor mistaken that the valve timing has 'mechanically' drifted and needs to be checked and adjusted? Seems to me that there can be no 'mechanical drift and the only adjustment needed is within the ECU. Then per nkfry's point why didn't he just operate the solenoids while it was hooked up? Or why not just reset the ECU anyway? The car has exhibited no signs of any trouble other than the hard starting due to the HP fuel pump. It runs well. What would you guys do next?