W123. Adjusting Valves the easy way. Advise from a Mercedes master to an apprentice - Page 2 - PeachParts Mercedes-Benz Forum

MB300Dave · #1 07-05-2013, 03:03 PM

Quote:

Originally Posted by dmorrison

Getting my daughters 83 240D ready to head back to Texas A&M on the 21st. She's going to go with it.

Decided to adjust the valves. I don't know about you guys but I've always felt the valve adjustment job to be one of those PITA jobs.
I have the Mercedes Service Manual, The Mercedes valve adjustment tools, The shop etc. etc. etc.
What I find is that when I loosen the top nut, which moves upward, closing the gap. Adjust the bottom nut to specs, (.30 for exaust, .10 for intake cold) and then you have it you tighten the upper nut WHICH CHANGED THE ADJUSTMENT. So you over compensate on the bottom one and then tighten the upper, Oops to much so try it again.
Out of frustration I went the dealer and talked to the W123 "Master". I shall pass on his words of wisdom since it took me 5 minutes to adjust the valve correctly using his method, and 4 of those minutes were rotating the Power Steering Pump bolt to move the camshaft.

He uses only 2 of the adjustment wrenches. One of the bent units and the large base unit.
Position the cam so that it is 180 degrees from the valve as shown in the Service Manual. Place the large base unit on the valve spring keeper washer as you would normally use the tool. Then feel the gap with the feeler gauge.

If the gap is to tight, then use the bent wrench on the LOWER nut and rotate it COUNTER CLOCKWISE ( looking from above) , do not loosen the 2 nuts.

If the gap is to loose then use the bent wrench on the UPPER nut and rotate it CLOCKWISE ( looking from above), do not loosen the 2 nuts.

It may be a firm rotation but it will rotate.

It's like this hugh light

came on. I could not believe how easy it was using his method.

Now this method may be debated, scorned, praised, defended, ridiculed, etc. But it took me 1 hour yesterday and I was not happy with the results. His method took 5 minutes (and as I said 4 of those minutes were waisted rotating the cam) and I was extremely accurate in my adjustment.

Knowing this group, and I do like this group, I'm sure some of you will not like it. But it is the method the dealer uses and he is the top W123 mechanic there.

So---Flame suit on

Dave

Thanks for posting, I will try it!

fpenglish · #2 07-05-2013, 06:27 PM

Sounds like a fairly promising method, I shall try it in a month and report back with results!

ROLLGUY · #3 07-07-2013, 01:57 AM

I am too scared to try it this way, and I have valve adjusting down to about 30 minutes total anyway. I would also need to get the big wrench if I was to try it. I have never needed more than 2- 14mm wrenches (one custom bent, and one straight) to do this job. After doing a few, you get to be faster at it. I do one cyl at a time in the firing order. I only need to turn the crank 36 degrees each time, then adjust the next one in the firing order.

Doktor Bert · #4 07-05-2013, 05:01 PM

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.

All I have ever done on a 617 is point the lobe at the spray tube and adjust...

1983/300CD · #5 07-05-2013, 05:09 PM

I forgot to try this method, though I want to and will soon.
-Unless anybody has discovered any negatives.
No stripped valve stems, or anything to report?

Hip001 · #6 07-07-2013, 11:56 AM

My first time adjusting valves. 2.5hrs taking my time to adjust and recheck. Used the regular way due to the fact I didn't have a wrench to hold the large nut. All 8 valves were tight. I did have a issue re-installing the valve cover. then found out the cam was in the wrong position not allowing the cover to slide by. once i rotated the motor it went right on.
Seems to start and run smoother.

ROLLGUY · #7 07-07-2013, 02:32 PM

Quote:

Originally Posted by Hip001

My first time adjusting valves. 2.5hrs taking my time to adjust and recheck. Used the regular way due to the fact I didn't have a wrench to hold the large nut. All 8 valves were tight. I did have a issue re-installing the valve cover. then found out the cam was in the wrong position not allowing the cover to slide by. once i rotated the motor it went right on.
Seems to start and run smoother.

I have found that after doing the valves in the firing order, the valve cover just falls into place after adjusting #3 (5 cyl).

Fattyman · #8 07-07-2013, 08:16 PM

I dunno about this. It would seem to me that jam nuts are designed to be tightened to prevent movement. And then loosened to allow movement. It's not that big of a deal really. Just adjust each valve as the lobe points to the oil rail and move on. Keep it simple. That's why the valve adjusting wrenches come in a set of 3. Use them

rscurtis · #9 07-08-2013, 08:22 PM

I would have to agree. Any time saved will be long gone after you strip the threads on one of the valves.

klei9843 · #10 08-25-2016, 06:01 PM

This is complete nonsense. It's been a few years, so hopefully you found another mechanic... Let's simplify:

Look at the design of the valve. Effectively, you have a threaded rod (valve stem) going through a hole in a cap that can spin (the part over the spring with the hex flats). You can rotate the cap infinitely, which rotates the entire valve as well. The only way to affect the position of the valve stem relative to the cap and the rocker is to turn the lower nut, which requires loosening of the upper one. If you rotate the locked valve nuts relative to the cap, spinning the entire valve, you are doing nothing. At best you are grinding the valve against the valve seat, which might knock some debris loose. Take a look at the design drawing.

1983/300CD · #11 11-01-2016, 08:11 AM

Worked for me. The large spring retaining "cap" as you call it prevents the valve from rotating while you adjust the nuts. What else would the function of that third wrench be? Or am I misreading your protest?

funola · #12 11-01-2016, 10:48 AM

Quote:

Originally Posted by dmorrison

........

He uses only 2 of the adjustment wrenches. One of the bent units and the large base unit.
Position the cam so that it is 180 degrees from the valve as shown in the Service Manual. Place the large base unit on the valve spring keeper washer as you would normally use the tool. Then feel the gap with the feeler gauge.

If the gap is to tight, then use the bent wrench on the LOWER nut and rotate it COUNTER CLOCKWISE ( looking from above) , do not loosen the 2 nuts.

If the gap is to loose then use the bent wrench on the UPPER nut and rotate it CLOCKWISE ( looking from above), do not loosen the 2 nuts.

It may be a firm rotation but it will rotate.

It's like this hugh light

came on. I could not believe how easy it was using his method.

.......

So---Flame suit on

Dave

I do not have the third wrench (will buy or make one soon) but agree with the above except that it may not be good for the threads if the 2 nuts are too tight initially.

Here are some pics and diagrams to help visualize. There is a key in the valve spring retainer and a key way in the valve stem and the two parts are locked together.

BillGrissom · #13 11-02-2016, 03:16 PM

I kind of follow that approach, but only at the final tightening. If the gap is on the tight side, I swing the top wrench more (moves top nut down), or if slightly loose I swing the wrench on the lower jam nut more. I check the gap when done and sometimes loosen and repeat. The way the OP describes it sounds like the jam nut isn't tight when starting the process. Probably takes 20 min to adjust all valves, after the valve cover is off. I have done it ~5 times.

I wonder why so much fuss in many posts about special bent wrenches and such. I have always used regular open-ended wrenches, though the lower one is short enough to swing between the injector tubes as I recall. It is from a cheap HF kit of all open w/ say 15 mm & 16 mm on one wrench. On the few occasions when I had the injector tubes off, that is a great time to adjust valves, but I sure wouldn't remove them for that task.

123boy · #14 08-19-2019, 10:56 AM

I realize this is a fairly old thread. About to do my valves, thought I'd review, now confused.
Not so sure about this procedure per the original post...a couple inconsistencies I found: (please keep in mind, I may be having a "senior" moment)
The poster states if the clearance is too "tight", turn the nut "counterclockwise". Unless these are reverse thread (never heard mention of that here), counterclockwise would move the adjuster closer to the rocker, thereby making the clearance smaller or the tolerance tighter, by closing the gap.....right?
He then states if the clearance is too wide, or loose, turn the nut "clockwise" to close the gap and make the clearance tighter. Again, clockwise would open the gap even further, making the clearance bigger or more loose.
I guess my confusion is with which way to turn the adjusting nuts? Logic tells me "CCW" will close the gap and "CW" will open the gap.
Am I missing something here?
Used to adjust valves "all the time" on my and my buddies VW's "back in the 70's"...we had a bunch of em. I realize this is a little different, but the principle and end result are the same. (guess I'm showing my age...

)

Diesel911 · #15 08-19-2019, 03:28 PM

Quote:

Originally Posted by 123boy

I realize this is a fairly old thread. About to do my valves, thought I'd review, now confused.
Not so sure about this procedure per the original post...a couple inconsistencies I found: (please keep in mind, I may be having a "senior" moment)
The poster states if the clearance is too "tight", turn the nut "counterclockwise". Unless these are reverse thread (never heard mention of that here), counterclockwise would move the adjuster closer to the rocker, thereby making the clearance smaller or the tolerance tighter, by closing the gap.....right?
He then states if the clearance is too wide, or loose, turn the nut "clockwise" to close the gap and make the clearance tighter. Again, clockwise would open the gap even further, making the clearance bigger or more loose.
I guess my confusion is with which way to turn the adjusting nuts? Logic tells me "CCW" will close the gap and "CW" will open the gap.
Am I missing something here?
Used to adjust valves "all the time" on my and my buddies VW's "back in the 70's"...we had a bunch of em. I realize this is a little different, but the principle and end result are the same. (guess I'm showing my age...

)

Sounds like you are used to valve adjustments where the adjusting screw is on the Rocker Arm.
In this case the adjusting Nut and Lock Nut are threaded onto the Valve Stem and the Rocker Arm which has no adjustment and the Camshaft are above the Adjusting Nut and Valve. You will quickly understand when you see it.

The first pic is just to show the relationship of the parts.

The pic on the right is to show the Valve Spring Retainer that you may need to hold to keep from rotating until the Nuts are loosened. The original Valve Adjusting Wrench set has a 3rd Wrench for that. However, there is alternative methods for holding it but don't put too much force on it.
Once the Nuts are loose it is not an issue.

When I did my first valve adjustment I had to use the 3rd wrench on 2 of them.

Thread Tools
Show Printable Version Email this Page
Display Modes
Switch to Linear Mode Hybrid Mode Switch to Threaded Mode