Interesting trick squeezing the PS belt for traction. I usually get a half turn or so with a flare nut wrench before it starts slipping on me. This is why I’ve migrated to the awkward but stalwart crank method.

Engine Turning
 

A paper clip or older pair of needle nose pliers you no longer care about will make a dandy/handy starter engaging tool, once you use it a few times you'll get a feeling for how quickly you need to jumper it so the engine doesn't crank too far....

I'm doing the valve stem seals on my 220D and I'm running into an issue. I don't want to drop a valve, of course, and I've got the #1/#2 rocker arms off. #1 cylinder is at TDC but if I unscrew the nut all the way, the valve is going to drop below the spring plate.
How do I compress the valve springs enough to be able to grab a thread on the valve?
Thanks all.
Phil Forrest

The Old Way......
 

Others here will know better but, if setting the particular piston to TDC doesn't work to hold the valves up high enough, remove an injector and carefully coil some cotton rope into the cylinder then *gently* turn the crankshaft until the rising piston holds the rope snugly against the pistons .

This is how it was done on O.H.V. engines from the 1950's onwards .

I got it figured out. The old seals were worn enough that they were dropping the valves. When I got the new seals in, the valves stayed up long enough to get the spring caps and the nuts on no problem.
Phil Forrest

Problem Solved
 

Yay .

Pictures would be nice.....

Not today. I'm the only one working on the car lately and I don't have time to stop, clean my hands, take a photo, then get back to work. If the GF were free to assist, she'd be on the camera but today was a workday for her and a welcome day off for me.

I got the valve stem seals on (some of them were an unholy pain to get to seat.) They are the all metal ones from Meistersatz. Anyway, got those on, torqued the rocker arm towers back down, hopefully to the proper torque (20.6ft/lbs). Then did a valve adjustment, this being my first time doing it with the injectors out, since I wanted better access to the valves and an easier time turning the engine over. Stuck new injector washers in, torqued those down, got it all bolted up, bled the lines turning over the engine a bunch of times. Tightened down the injector lines and it started up. Loudly, but once I bled the air from the lines, it calmed down and made a nice clacketyclacketyclackety sound of a cold diesel. I let the car fully warm up to 175 then shut it off for the night. I'll drive it on Saturday.

Phil Forrest

You would need to remove the Pre-chamber to do that. And if you had the pre-chamber removed with a strong light you could see the top of the piston at tdc.

When I did mine I of course left the Cmanshaft n place and removed the Rocker arms and likely some Glow Plugs so the engine would turn easy.

When Number One is at top dead center on the compression stroke the camshaft lobes for the number one cylinder are in kind of a "V" configuration pointing upwards.
When you rotate the Engine to get to the next one same upwards "V" configuration is what you want to see on the next Cylinder you intend to do next and it will be at or extremely close to TDC.

I don't recall having any issues compressing the valve springs and upper plate to get the valve stem nuts on. I also don't recall what I did to do that. However, the Camshaft is there and you can get something between the shaft and the top spring retainer so you lever it down and compress the spring.

Step 12 is compressing the valve spring.

http://www.peachparts.com/shopforum/diesel-discussion/203902-replaced-valve-stem-seals-my-experience.html

I assume we#re talking about the ol Indian rope trick. I did it myself on a gasoline six cylinder 300E. Here's wht i can share with you.



To anyone who's done this:

1.)Say I'm on cylinder one. I move the cylinder up to it's highest point. Am I now clear to service both intake and exhaust valves? I'm assuming yes, but again, don't want to drop a valve.

If you have stuffed the maximum amount of nylon chord into the pot and you turn the crankshaft so the piston rises, you will feel it when the piston pushes hard against the chord and can't go anywhere. Don't be too scared. its pretty elimentary.



2.) How does one confirm that the cylinder is at its highest point? I imagine the crankshaft dial is what gives this info in terms of degrees? What's the math?

You will just feel it as i explained in point #1


3.) I start at cylinder one -do I then follow the firing order?

No. No need. If you want to, by all means do, but the point is htat you're looking for both valves to be i nthe closed position, which means TDC on the firing stroke

4.) Anything else I should know? I've found the torque values for the rocker arms, the rest seems to be setting the valves again once everything's been replaced.

Be careful with the chord. it has a habit of getting stuck when you try and pul it out. I guess it can catch somewhere. WHat i should have done is greased it to be on the safe side.

Easy job, but time consuming.

_[/QUOTE]

I did my OM617 stem seals this weekend, it was not difficult to get each cylinder to TDC.

Start with #1 at TDC on the compression stroke, rotate the engine 144 degrees then do #2 then rotate another 144 degrees and do #4 and etc. The order is 1-2-4-5-3 just keep turning 144 for each cylinder. When I removed the nut and cap I pushed a small screwdriver through the valve spring to keep tension on the valve stem so it would not drop down. With the cap off I could grab the top of the stem with my fingers and slowly lower in down to test it. In all cases the valve stem only dropped down about 7mm. There is no need to try and stuff rope in the cylinder the piston keeps the valves up.

I made up a template in AutoCad (attached) so I could mark 144 degrees on the front crank pulley with a sharpie as I went around. If you print this at 8.5 x 11" the circle should be same diameter as the pulley. Note: this template is for the 5 cylinder engine only.

Tim

[/QUOTE]

There is a serious issue with your idea. You cannot put a cord or rope into the cylinder because there is a pre-combustion chamber that is going to block the passage.
The bottom of the pre-combustion chamber only has small about 1/16th of an inch holes in it.

Pulling out one pre-combustion chamber means removing the Injector and the Glow Plug and the pre-combustion chamber retaining ring needs a special tool to remove it and you also need a special tool to pull out the pre-combustion chamber.
To assemble it you will need one of the special tools and a torque wrench that goes up to 180 Nm an new seal ring for the pre-chamber and a new heat shield for the Injectors.

So you can do all of that on each cylinder in order to get a rope inside of it or you can just rotate the engine till the intake and exhaust cam lobes on the cylinder you want to adjust the valves on form a "V" shape that is straight up.
That tells you are are at TDC or very close it. That is what I did when I changed my Valve Stem Seals and it worked fine.

On gasoline engines one of the methods to hold valves in place to change seals and or springs if you had an air compressor was to use a compress tester adapter that screws into the spark plug hole after the plug is removed and fill the cylinder with compressed air.

Happily I have only read about that. However it ought to work on Diesels.

Air To Hold Valves In Place
 

This only works if you have a large compressor with serious air volume...