Graham,
I have the paper manuals and have read them... but I am not going to get them out for this question... so let me put it these ways... one.... the FSM says to use the crank nut... that is not the ps nut...and not the cam nut...
Two... TCane and I worked for an hour getting a ps nut off one time... and had power equipment and oxy acet... it is TAPERED ... therefor you can over tighten it... but it is your car and you can do what you want with it... my obligation is to raise red flags for those that have not gotten caught by some PO's actions or have the FSM to read themselves....

I checked both the Maintenance manual and the FSM and neither said anything about not using the PS pulley nut. If you have MB reference that confirms that we should not be using the PS pulley nut I would like to read it and would certainly take note if what you say is confirmed.

It SAYS use the CRANK NUT...
it does not have to also say ... ' do not use the steering wheel nut, the rear axle nut, the radio nut '.....
But I am telling you that due to its being a tapered fitting... it is not legit to turn the entire engine over with it.... I actually think it does say ' do not use the ps nut'... but do not have time to look it up ...

Link to FSM section on valve adjustment:

http://www.startekinfo.com/StarTek/outside/12265/disc_2/program/Engine/617/05-210.pdf

Notes to use crankshaft bolt. Says specifically not to use camshaft nut. No mention of power steering nut.

Feel free to use the PS NUT.... it is your car.... I assume....
smarter people will read the instructions to USE THE CRANK NUT...and USE THE CRANK NUT...

I was thinking of throwing a few lit matches down the dip stick tube instead of pulling the drain plug at oil changes. The FSM does not say you shouldn't do it that way. By the way do you (or anyone) know the torque spec on the radio nut?

The FSM does say to use the crank nut, and specifically not the cam nut. Maybe it is the cam nut shaft that is tapered and not the PS pump? I see no reason why the PS pump shaft would need a taper. That said, I don't use what the FSM recommends. I do not use the PS nut simply because it will over torque it in the process. I use a remote starter switch which is the easiest and quickest way. I adjust what ever set of valves that are pointing up and mark each on a sheet of paper to keep track. When done, I check each valve again just to be certain.

If I follow the FSM, I would have to add at least an hour of time. For those who use the crank nut, do you do it from below (it is not possible for me anyway to do it from above)? That means having a helper or add more time if you don't have a helper by having to get up and down many times to point the valves up. Good exercise but no thanks.

The CAM NUT is stong enough to rotate the engine with....
The REASON not to use it is that the whole system is designed with respect to keeping the timing chain tight between certain points in the rotation... the slack being addressed on the passenger side of the engine by a combo spring,ratchet and oil pressure.
This is why the FSM specifies that when ' rolling in' a new chain pressure is to be kept on the combined chains...
If you use the CAM NUT then you are PUSHING A CHAIN... thus not keeping the designed tension on the side of the engine meant to keep the chain in contact with the sprocket of the timing pump and things like chain rails.
We have had many reports from people who thought they ' just replaced' the chain... and found the timing pump a tooth off afterwards...
But some people do not believe the FSM.... after all it was only written by the people who built the car...
TCane and I spent an hour taking a PS nut off a car he bought ....with oxy acet and many heatings and lots of force..... that is when we found out it was tapered...

OK so you have verified the PS nut is tapered. Usually a taper is used for an application where precise timing is needed such as in a VW camshaft or injection pump shaft. Why was a taper used for the Mercedes PS pump?

I don't know what the big deal is about using the PS pump pulley. I have never had to remove a PS pulley, and don't ever plan to do so. It is not worth the effort to rebuild a PS pump when there is so many good ones available. Like most everything else on these cars, it is designed and built very well, and should last the life of the car (in most cases they do). I have had almost 30 of these cars, and only once have had a leaky PS pump that needed fixing/replacement. I have several laying around, so finding a replacement is not hard. I would not bother removing the pulley for any reason, I would just replace the entire pump. As far as using the crank pulley over the PS pulley, most always I am able to use my 27mm deep socket on a 1/2" ratchet just fine. If I do it just right, it stays on the bolt and does not fall off while I am adjusting valves. In fact, it has happened several times that I left it on the crank bolt and started the engine minutes later after putting everything back together. I have gotten the valve adjustment down to about a half hour total now. The times I can't use the crank bolt, I used the PS pulley and it worked just fine. I see no problem with doing it whatever way works best (easiest). I am not going to NOT use the PS pulley bolt for fear that I won't get the pulley off, because I probably will not ever have the need to remove the pulley in the first place........Rich

I do use the "CRANK NUT".

I was just relaying what the FSM actually says since there was a lot of speculation going on and you "do not have time to look it up" (though you do have time to respond and berate).

You said you believed it stated explicitly not to use the PS nut. I was simply correcting that. It does not say that.

That was not a suggestion to use it.

I will choose not to take offense at your low-blow at my intelligence. :)

Actually I think that where precise timing is needed a key is more often used..
A tapered (friction ) fit is often used to protect something in the power line...as with using the friction of a Morse Taper in a lathe... where you WANT it to give way under certain drastic situations and limit the damage by letting the power go on down the line..

For timing a VW diesel engine, the cam nut is left loose while engine is rotated to TDC before the cam nut is tightened. In the VW, the taper on the cam is for precise timing, not for protection of the cam, which bends valves and breaks the cam if the engine goes out of time for whatever reason. The taper IMO is for precise alignment of the pulley for less pulley run out and wobble, same reason the morse taper is used in morse taper drill bits.

I'm with ROLLGUY on this one. I've got a spare pump (actually an entire spare engine) so dealing with a failed pump is a simple swap...nothing to do with swapping a pulley.

Well, you don't believe the Mercedes people who wrote the FSM...
and you have not been reading the same books on machine design that I have.. or you did not believe them either...
I can't help you under those conditions.