Valve stem seals (om616/617)
 

Seems like a straight forward job. Only thing I'm not clear on is how one confirms that each piston is at its highest point. I don't want to drop a valve into the bore...

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.

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?

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

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.


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1 and 4 will be together on TDC (1 on compression, 4 on exhaust). You can service both valves in both cylinders 1 and 4 at the same time. Turn the crankshaft 180˚ and you'll now have cylinders 2 and 3 at TDC (3 on compression, 2 on exhaust). Obviously it's more complicated for a 5-cylinder or 6-cylinder engine, but the 4-bangers are pretty simple.

I'm not saying you cannot do it that way; but, it is usually done with compressed air to keep the valve in place. With compressed air it is better to have the piston at BDC vs TDC to prevent pressure from pushing the piston down and unexpectedly turning the engine.

If both cam lobes on the cylinder you are working are teetering/see-sawing between opening and closing, that cylinder is TDC on the exhaust stroke. If the crank was turned exactly 360 degrees, that same cylinder would be TDC on the compression stroke.

For the purpose of doing valve seals without air, TDC compression vs exhaust doesn't matter.

IIRC, the intake and exhaust seals are different, sort them before starting the job.

Good luck!!!

agree.

6 cylinder is easier than a 5 cylinder (6cyl has tdc at 3 points while 5cyl has them at 5 different points)

on om617 if you don't do it with compressed air or have prechambers out for some reason to check tdc you have to do this:

starting at #1 cyl at tdc you mark the balancer and rotate the crank 144 degrees between each cylinder and you do them in the firing order: 1-2-4-5-3

Thanks guys.

I just got the seal “kit” from pelican.
The new seals are all identical. No differentiation between intake and exhaust. I guess this was an update some years ago.

The “kit” is not actually a kit at all. None of those plastic sleeves for protecting the valve threads were included. I called for a replacement, but how essential are they? Is there anything else I could use in lieu of?

Valve Guide Oil Seals
 

My factory m-B trained friend told me long ago to only use the exhaust seals, maybe they've up dated and only provide them in the kit now .

The thing plastic installation tool prevents you from nicking the seal lips on the grooves in the valve stem that holds the valve collets .

It's been forever since I did this job and never on an M-B but a little bit of oil in the valve stem and twist it as you *gently* work the new seal over the valve stem should do the trick .

I think spending some time looking at you tube vids might be wise, maybe one of them has a simple DIY installer trick .

Wrap the threaded part of the valve stem with tape or heat shrink tube.

Excellent tip.

And thank you all for pointers. I now have a much better conceptual understanding of the way these things move.

Roll it to TDC on Number 1 and you will see that tips of the camshaft lobe forms sort of a "V" pointe upwards note that position. Make sure very valve you release is when the lobe are making that V shape with the tops of the V pointing upwards.

Also being sure you are turning the engine in the direction of normal rotation you can watch the firing order.

You are going to be reusing some of the little protective sleeves that slide over the threads on the Valve stem.

I used a pipe bushing to push the seals down.

That is for gasoline engines because gasoline Engines usually have a volumes combustion chamber right over the top of the piston and often shorter valve stems. There would be a longer distance for the Valve to drop before it hits the top of the piston.

Maybe it can only be done without air on Mercedes diesels. In any event on the 617s when the Piston is at TDC there is very little space between the top of the Piston and the cylinder head.

The attached pic is of a Mercedes 180D but you can see that when the piston is at the top there is little room for the Valves to drop.

You can cover the valve stem threads with scotch tape. They are also color coded.

I used the Meistersatz kit years ago and it came with 4 of the protective sleeves.
http://www.peachparts.com/shopforum/diesel-discussion/356451-300sd-om617-valve-seal-replacement-help.html

Installation Tool
 

? Maybe some one has this tool left over to share with Shern ? .

Do the valves for each cylinder in firing order. Piston needs to be around TDC in compression stroke, the position of the cam lobes and the balancer markings will help you.

You will have to let the valve rest on the piston top as you slip on the sleeve(the tape or the heat-shrink tube) or remove the valve spring if you decide to,it is alright and inevitable. As long as the piston is around TDC you will not lose the valve.You do not need compressed air . And you can always slowly press on the valve spring retainer before disassembly to see how much drop there is before the valve kissing the piston top.

The job is pretty straight-forward, just some notes that are important:

-clean the rocker towers screw holes in the cylinder head from collected oil before assembly !!! Make sure the all centering sleeves are there.

-you may want to remove the springs and valve rotators. Clean and blow the rotators with brake fluid,check for ease of movement,dip in oil before reinstall .Clean the nest of rotator from old oil and debris.

-the rocker arm tower assemblies need to go back in the same position. The rocker arms should not be under stress by the cam lobes on removal and reinstall(this means the valve nuts may need to be screwed in a bit more at RAA installation).

-If you need to disassemble the rocker arm assemblies make sure each rocker arm takes the same position before reinstall (to go with its mated cam lobe again).

-Check the Rocker Arms Assemblies' securing springs(there might be excessive wear on their very ends caused by the movement of the rocker arms). Replace if needed.

-It is a good idea to have at least one spare valve nut (the bottom one).Clean carefully each threaded surface.

-use whatever suitable for pressing in the valve seals. I used a big M16 flat washer cut on both sides.The pipe bushing is great too.

-FSM gives "torque reference value of 20-30 Nm" for the valve nuts.

-You may want to change the valve springs or measure the chain elongation too.

Basics
 

It's really important to measure the valve springs any time they're off the engine and yes, I know : ! more tool$ to buy ! .

What the DIY tip is : line all the valve springs up in a row and lay a straight edge over them ~ if any are not *exactly* the same height either buy all new ones (best) or at least take all of them to any Machine shop and ask them to test them as once one is beginning to go, more are also close to failing .

Point of clarification -what holds the valve in place, the stem seal? The nuts? If I’m doing one cylinder at a time, I’m wondering how I’m supposed to line up all the springs without dropping a valve?