N62 valvetronic servo question

[gaffinfool]

I'd like to think I'm pretty mechanically inclined. I'm 43 and I have been wrenching on cars my whole life. It took me 8 1/2 hrs total the first time I did it, with BASIC hand tools in my driveway. This time it took me 2 1/2 hrs Saturday to tear it back down, but now I have a compressor and air ratchet (sure takes the monotony out of long winded metric bolts), and about the same last night to put it back together, but I didn't have to continue onto the timing chain cover. There are a lot of wires and such you have to move, then pull the solenoids out, and swing the alternator down before you can unbolt it. Thinking back, that would eat the crap out of another 3 hours, so yeah, about 8.5 hrs if you stay at it. There's just a lot of crap in the way that you have to relocate just to get there. Now, from what I've read, you *can* do the timing cover without removing the valve cover, but I would think you would be risking the valve cover gasket leaking if you did it that way, but that's just my opinion. You will also want to change any o-ring/seal you bother along the way.

TL;DR - 8.5 hrs in the driveway with basic hand tools

[blndweasel]

OK I have to jump in on this one. This is my first post in the forum, and I know this thread is old but I'm currently doing my first N62 overhaul and have been forced to learn up on the valvetronic servomotor operation.

The servo motor is just a DC pole motor. Under current, it turns, and if the polarity is reversed, it turns in the opposite direction. It will turn as long as current is applied, and this is controlled by the engine computer (I couldn't tell you which module, I'm not that far in but my guess is the DME).

The thing that affects eccentric shaft movement are the mechanical stops, and these are part of the eccentric shaft mechanism, not the valvetronic servomotor.

I, too, had my servomotor "pop" out the first time I removed it (both sides, actually). I had done extensive reading and knew this could happen, but what isn't adequately described in the Pelican Parts article, or any place else I've found is just how much tension the motor can be under, depending on the position of the eccentric shaft when the engine was last shut off.

Despite cracking the upper casing / seal on the servomotors to gain access to the 4mm hex, and despite preparing to unthread the servomotor worm gearn using said 4mm hex, I was not able to hold the servomotor in my other hand due to the sheer tension on the eccentric shaft. There was just no way I could do this with two hands, I would have needed an assistant to hold the motor and/or unscrew the servo worm gear.

Now after studying the eccentric shaft mechanism, I believe the Pelican Parts article could better describe the process of removing tension from the eccentric shaft / servomotor by turning the servo 4mm hex clockwise PRIOR to unscrewing the 4 mounting screws. This will remove spring tension sufficiently to be able to remove the motor free-handed by either spinning it or turning the 4mm counter-clockwise until it releases. I found that spinning the motor is more reliable, sometimes turning the 4mm hex will start moving the eccentric shaft instead of backing out the motor.

A rather frustrating point of all this, is the proper way to prepare the servomotor for removal is to run the corresponding ISTA-D Service operation. But to run that operation, the first step is "start the engine and allow the vehicle to idle." Well, in my case my valve covers were leaking oil extensively on the headers, and engine operation was not desirable. So, I'm left with a manual override (if we want to call it that) to remove tension on the eccentric shaft using the process described above.

Back to my response to your question - was the cause of your problem the eccentric shaft position sensor, or the servomotor? I do not think there's anything you can do in removing the servomotor to affect eccentric shaft limits, all you can do is potentially damage the eccentric shaft gear teeth and/or stop limit as the shaft snaps back to its hard stop when the servo motor pops out.

Prior to starting the engine up, if set to ACC position, the servomotor will drive and then reverse to re-learn the eccentric shaft stops and commit them to the DME for operational limits. If the shaft sensor detects implausible values, that's when you'll get a code.

Once running, I believe INPA can display eccentric shaft position data to determine how much "play" exists in the system (e.g. worn gears on shaft).

I have a great link to share which was very informative in my research, but I'll try to post it separately since this is my first post and I suspect the board will assume I'm a SPAMMER because that seems to be a major fear based on everything I read during the registration process.

[blndweasel]

Here's the article. Super helpful - especially the diagram, although it's of a second-generation valvetronic system, not a first generation system as found on the N62.

https://www.searchautoparts.com/auto...stems?page=0,0