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

dmorrison · #1 08-15-2006, 09:54 PM

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

Johnhef · #2 08-15-2006, 10:02 PM

I'll give it a try next time, i hadn't heard of doing it that way before. I have to redo the ones on my 83 anyways soon.

waybomb · #3 08-16-2006, 08:46 PM

Wish I would have known this 13 days ago!

dmorrison · #4 08-18-2006, 01:58 AM

I'm surprised the group has not made very many comments on this.

Dave

Brian Carlton · #5 08-18-2006, 08:36 PM

I can relate to the change in readings the moment you touch the top nut.

The new procedure sounds promising. However, the capability of rotating that pair of nuts is dependent on how tightly they are locked together. If very tight, I can envision quite a struggle to rotate them.

But, I might just buy that lower wrench and give this procedure a try. My problematic lower back will thank me profusely if this procedure is successful. The factory procedure is definitely a 90 minute job........and no fun at all.

dmorrison · #6 08-18-2006, 09:02 PM

If the top and bottom nuts are jambed very tightly. I would loosen them a bit and tighten them to a more correct tightness. That way the procedure will work better. I found some valve nuts to be that way and retighten them to a more comfortable setting. I then found the proceedure worked fine.

Dave

Carson357 · #7 08-18-2006, 09:35 PM

one thing i can add about the adjustment is this, if you can use a remote starter switch or make your own i have found a great method for the adjusting sequence.
first remove the valve cover and connect the starter switch
bump the starter until the first lobe on the first cylinder (exhaust valve lobe) is pointed toward the oil tube. if you notice there is the one pointed to the oil tube and one pointed straight up. the one pointing to the tube is the exhaust ant the one pointing up is the intake,(the exhaust lobes will always point to the tube and the intake lobes will always point straight up.) adjust them, bump the starter, if you look there will be another one pointed toward the tube and another pointing up, continue adjusting and bumping the starter until the original exhaust cam lobe is back pointing to the tube, once you are there they are all done. the only times i have seen this not work is when the compression is low, or if the valves are too tight causing low compression. this is how i do it when i service customers cars at work.

pdrayton · #8 08-18-2006, 09:50 PM

Nice one!

I had a big DUH, why didn't I think of that!

Thanks for sharing!

TheDon · #9 08-18-2006, 09:58 PM

Quote:

Originally Posted by waybomb

Wish I would have known this 13 days ago!

yea same here

my problem is i cant fit a regular 14mm wrench is it.. or w/e on the bottom nut.. what i would do is loosen both nuts so i could adjust them with my fingers, get the correct gap and put one bent wrench on the uppermost part of the large nut and tighten the bottom one..

a good way for me was to actually lay into the engine compartment and have a thin wrench from the leftside come in and hold that top nut while tightening the bottom one

sailor15015 · #10 08-18-2006, 10:49 PM

That sounds like a good way to try it but I'm supprised to hear about all the people that have so much trouble with the factory method. It didn't take me that much time, and I even have straight wrenches. I think I'll give this way a try next time, though, because sometimes I have to really get those wrenches just right to get those nuts loose.

TheDon · #11 08-18-2006, 11:08 PM

Quote:

Originally Posted by sailor15015

because sometimes I have to really get those wrenches just right to get those nuts loose.

or when adjusting.. i was stuck on cylinder 3's exhaust because i could not get the wrench to slip onto the nut to adjust it no matter how hard i tried.. a good set of wrenches for adjusting would have to be about 3" long with the ability to attach the stupid angled piece on for loosening and use the 3" for fitting into the tight spaces..i need to make some wrenches like that and see how they work

Hit Man X · #12 08-18-2006, 11:35 PM

Good info, I need to do mine at the years end.

1983/300CD · #13 08-20-2006, 08:14 AM

Or, why not adjust the top, cap nut to the proper gap (hold it with one wrench), then bring up the lower locking nut (with the second wrench) to meet it?

#14 08-20-2006, 04:00 PM

I'd think that if you can turn both nuts at the same time, they are not tight enough.

Quote:

Originally Posted by 1983/300CD

Or, why not adjust the top, cap nut to the proper gap (hold it with one wrench), then bring up the lower locking nut (with the second wrench) to meet it?

AFAIK, that's the right way to do it.

TheDon · #15 08-20-2006, 04:03 PM

Quote:

Originally Posted by 1983/300CD

Or, why not adjust the top, cap nut to the proper gap (hold it with one wrench), then bring up the lower locking nut (with the second wrench) to meet it?

thats what i did essentially.. but i adjusted with my finger to the point i wanted then held the nut with the wrench... the bent wrenches suck...