[85Turbo]

I did the valves on my 85 Turbo today. I set the Exhaust to .015" and Intakes to .006" at about 80-85 degrees Farenheit. (My feeler Gauges do not have metric they are old ) anyway, after rotating the engine through and re-checking all of the valves, I found that the adjustments had changed, so I went through and did some of them again, after rotating a few more times I found the same issue. Any suggestions on whats causing the valve clearence to change on engine rotation?

 

[300Dman]

One of the Members of another forum suggested that the Valve Rotator position can sometime throw off the adjustment. Unfortunately I did not put his exact words in my notes so I cannot say exactly what he did nor do I remember his remedy for the situation.

I have always done my Valve Adjustments with the Engine cold and I crank the Engine over several times and re-check them.
I have had a few of the Adjustment slightly off; re-did them and cranked again. After that they were OK.

Wear is another thing that can make a Valve adjustment not hold. Wear in the Rocker Arms and also the Valve Stem/Guides.

 

[Nutz 4 Benz]

Just curious, do they sell valve lash caps for 617's?

 

[Govert70227]

80-85F is cold for valve-adjustment purposes, so the clearance should be 0.004" intake and 0.014" exhaust.

Valve clearance decreases slightly during tightening of the nuts, because the adjusting nut moves up a bit in the thread. Did you check the clearance after tightening?

Also the engine cooling down - helped by the removal of the valve cover - will decrease valve clearance.

If you haven't used the third key, and the rotocap (valve rotator) doesn't work anymore, you could rotate the valve off its position on the valve seat. If the valve rotator doesn't work, the valve seat will wear out unevenly, causing the valve to seal properly only in one position.

If the valve rotator does work, but the valve seats are worn out unevenly or there is a deposit on the valves, rotation of the engine can also change the valve clearance.

@ Nutz for Benz

They are not available and they are not really necessary on diesel engines. Usually the compression runs out before the valves run out of adjustment room.

 

[85Turbo]

Thanks guys, I have the Hazett wrenches, and I was wondering what exactly the purpose was of the wrence that sits on top of the valve spring. What exactly do you mean by the rotator? what is the purpose of the tool? thanks!!!

 

[Govert70227]

Below you can see a diagram of the valve, valve spring, rotocap and camshaft of the OM61X engines.

Below the spring you can see the rotocap or valve rotater. Below you can see a picture of a rotocap:

It is spring-loaded and it acts like a turntable. Every time the valve is pushed open and the valve spring is compressed, the rotocap will turn a little bit causing the valve spring and valve spring cap to turn too. Because the valve spring cap is locked together with the valve itself by means of a notch, the valve will turn too. This is done to prevent an uneven wear on the valve and valve seat. If the valve wasn't turned, it would move up and down in one position, causing an uneven wear.

The problem is that the rotocap itself can wear out, so that the valve isn't turned anymore. That means that the valve and valve seat can wear out unevenly and the valve only is really closed in one position. If you adjust the valves in this situation without the use of the third wrench to hold the valve spring cap, it is possible to turn the valve, away from its position where it closes completely. That means that the valve clearance may change and, more importantly, there is lack of compression.

Some pictures:

Here you can see the valve spring cap with the notch which locks it to the valve itself:

here you can see an old rotocap being removed:

Here you can see a new rotocap installed at the base:

 

[85Turbo]

So when doing valve adjustment, try to not spin or rotate the valve if possible?

 

[RogerB34]

Yes - wedge with a screwdriver if possible.
Do all once and then recheck.
Opinion: Use the starter and position the valves between 12 and 2.
Because the cam radius is the same.
Haynes says 1 and that requires manual turn of crank pulley to achieve accuracy.
Ok if assistant available.
Recommend two valve cover gaskets on hand.
Took me two times to get it to my satisfaction and reuse of gasket resulted in leaks.
I used Mercedessource kit wrenches. Very good quality but too heavy. Cut 3 inches off the handle and much better. Wrenches lighter weight EBay.

 

[300Dman]

Thanks guys, I have the Hazett wrenches, and I was wondering what exactly the purpose was of the wrence that sits on top of the valve spring. What exactly do you mean by the rotator? what is the purpose of the tool? thanks!!!

I also have the Hazet set. I was told the 3rd Wrench is there to not only keep the Valve from Rotating but sometimes one nut will loosen and the other one will not.
The Wrench again keeps the Valve from rotating and allows you to loosen that stuck Nut.

The first time I did a Valve adjustment I had 2 Nuts that were stuck. And, the 3rd Wrench took care of that but was awkward to use.

Once the 2 Nuts were loosened I have never had to use the 3rd Wrench again.

 

[radhikacreddy]

valve clearances not holding

I posted this in another thread, but am trying again here in hopes of getting more answers. Apologies for the redundancy.

I have done several valve adjustments on my '83 300TD, and have found the clearances don't hold. When I tighten the locking nut up to the adjusting nut, they just spin together. As I understand it, the when the lower locking nut is tightened against the upper adjusting nut, both nuts should be "locked" in place and not spin at all.

Is it possible that I over tightened during my last valve adjustment, and stripped the valve stem threads? If so, is this a fixable problem?

 

[300Dman]

I posted this in another thread, but am trying again here in hopes of getting more answers. Apologies for the redundancy.

I have done several valve adjustments on my '83 300TD, and have found the clearances don't hold. When I tighten the locking nut up to the adjusting nut, they just spin together. As I understand it, the when the lower locking nut is tightened against the upper adjusting nut, both nuts should be "locked" in place and not spin at all.

Is it possible that I over tightened during my last valve adjustment, and stripped the valve stem threads? If so, is this a fixable problem?

There is more than one thing going on. If the Valve have not been adjusted for a long time there is deposits on the Face and seat. People say to run the Engine 500 Miles and re-do the Valve Adjustment.

I have read that the Position of the Valve Rotator makes a difference but that was not clearly explained.

This is what was said in an other thread; Adjusting Valves Dr Bert Post 47
"Valves will have a degree of runout, if only a thousandth or two. As you rotate the valve, you will feel a tight spot where you lose some clearance. This is where you want to adjust the clearances; at the tightest point. Otherwise, as the valve rotates, it will reduce clearance in the area that has the most runout."
W123. Adjusting Valves the easy way. Advise from a Mercedes master to an apprentice - Page 4 - PeachParts Mercedes ShopForum

On other Engines that do not have Valve Rotators if the Rocker Arm Bushings are worn and the Valve Stem has side paly beyond spec it is difficult to get the Valve Adjustment to hold.

I just thought of this so I have not tried it. Has anyone tried getting something on the Rocker Arm to push the Valve up and down a little to see if that changes the valve Adjustment Clearance?
This might rotate the Valve Stem to that sweet spot.

 

[300Dman]

I have not re-read this but it was in My Notes.
Valve Rotors effecting the valve adjustment, valve rotor part number
http://www.benzworld.org/forums/w12...-617-valve-adjustment-issues.html#post4945900

Also may People appear to have done the Valve adjustment with out too much re-checking and have had their Engine run better. So the adjustment might not be as touchy as is made out.