I have a question for a mech. On the valves of the 617.951 diesel there is the cap nut and the jam nut. When I look at the pictures in the manual it appears that the jam nut holds the valve spring compressed. If this is the case when the valves are adjusted won't that change the tension on the valve spring?
Or am I wrong (sure hope so)?

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Mark
82 300SD 100k
91 Caprice SS
92 Jetta TD

The change in the spring tension will be so small you will never know it,and neither will the valve.
Bill Lewallen Lexington,Ky.

Thanks for the reply. I just needed someone to confirm what I thought. Just seems like a second rate way to do things when there are better ways. I could not dream that MB would do it this way. Oh well.

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Mark
82 300SD 100k
91 Caprice SS
92 Jetta TD

MB has used this method of adjusting valves on diesels for years. I know since 1958. One of the many MBs I have owned over the years was a 180D and the valves were adjusted by the same method. I don't know about the newer models.
Bill L.

Bill;

I can see that it works as time has proven that. It just seems a little odd for this caliber of engine. I am used to heavy duty diesels that would never consider this method. But, I will go ahead with my valve adjustment with no surprises.

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Mark
82 300SD 100k
91 Caprice SS
92 Jetta TD

I would have to go back and look to be sure, but I thought that the top nut is the adjuster which lengthens the stem, the bottom one is the lock nut. If I am right, and I wouldn't bet on being right until I look at it again, this does not change the length of the spring. I'm now very anxious to go take another look.

Good luck,

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Larry Bible
'01 C Class, Six Speed
'84 Euro 240D, manual, 533K miles
'88 300E 5 Speed
'81 300D Daughter's Car
Over 800,000 miles in
Mercedes automobiles

Larry;

Now you have me confused. Please let me know what you discover. This little question really has be wondering now. From looking at the pictures I cannot see what holds the valve spring other than the jam nut.
I await your reply.

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Mark
82 300SD 100k
91 Caprice SS
92 Jetta TD

Maybe we could just grind off some of the valve stem like the old Ford V8s which had no adjustments.
Actually as the valve wears into the head, the end of the stem is closer to the cam and the spring gets extended slightly.The acorn nut must be screwed onto the stem farther to keep the clearance correct. Thus the length of the spring is the same after adjustment as when new. But all this is just a few thousandths of an inch and is not significant.
The top acorn nut does the adjustment, the lower nut is the lock nut. Make sure the lock nut is tight. I had one come loose once on a 220D and the valve went into the cylinder and the piston came out the oil pan (I didn't do the valve adjustment). The engine still ran on three cylinders but of course had no oil.

P.E.,

My dad had an independent garage after WWII through the fifties, and could make the old Chevy sixes and Ford flatheads sing.

I bought a really nice forty Ford in the early seventies. It ran and sounded so good when I bought it, you almost had to look at the oil pressure guage when sitting at a traffic light to ensure that the engine was still running.

My dad said that the valves weren't too bad, but they weren't exactly right. He couldn't stand it and ground them by hand and adjusted them. It was amazing. After he was done with that and setting the vacuum brake on the distributor(remember that), you absolutely did have to look at the oil pressure guage to ensure that the engine was still idling.

These engines were simple in a lot of ways, but it took mucho skill to really make them right.

Sorry to post this here, but I couldn't help myself. I hope you enjoyed it.

Have a great day,

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Larry Bible
'01 C Class, Six Speed
'84 Euro 240D, manual, 533K miles
'88 300E 5 Speed
'81 300D Daughter's Car
Over 800,000 miles in
Mercedes automobiles

It is always fun to hear what people have done to their engines. It is amazing how some engines just plain run better than others even though they are the same.
Back to my valve question, in most cases of adjustment is the gap too big or too little. The valve should wear into the seat and the gap should get smaller. Is this the case?

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Mark
82 300SD 100k
91 Caprice SS
92 Jetta TD

Yes, the clearance gets smaller and the valve spring gets longer. If the valves are not adjusted, they start to leak because when the clearance is gone, the valves cannot close tightly.

Larry:
How did those old engines run without EGR valves, catalitic converters, electronic ignition, throttle sensors, computers, electronic fuel injection, etc. That's why I like my MB Diesels: most of the latter parts are not used and therefore can't fail and I can fix almost anything myself. I think that $50 - $60 an hour to have my car repaired is obsene. They should arrest people who charge this much for obsenity, not the dancing girls!
P E H

P.E.,

Answer: They ran very well.

Seriously, although they were simple to maintain in a lot of ways, the efficiency and long term reliability that comes with modern engines is remarkable.

In those days, if you knew how to keep them running right, you would get complements. Most people did not know how to put in new points and plugs periodically and get everything adjusted right. I kind of miss the pride that was involved, but at the same time, the lack of required maintenance and the extended mileage we get from modern engines, more than makes up for it.

I guess the time has come now, that there is a whole generation that would not know what a set of contact points were, if you put them in their hand. A dwell meter would probably be equally foreign.

I remember when I was young, hearing the "old guys" talk about Model T ignition coils and generator cutouts. Our technology is ten times past the sixties technology. The early sixties technology was probably only two or three times past the twenties technology. In the mid to late sixties, we saw quite alot of basic innovations come about; disk brakes, alternators, all synchro transmissions, and even the beginnings of electronic ignitions.

As far as trouble free motoring goes, we are light years ahead. The price, of course, is a complex troubleshooting path when we do have trouble. Thank goodness, that's not real common.

Would one of you young whipper-snappers hand me my walking cane?

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Larry Bible
'01 C Class, Six Speed
'84 Euro 240D, manual, 533K miles
'88 300E 5 Speed
'81 300D Daughter's Car
Over 800,000 miles in
Mercedes automobiles

Real quick comment about PEHs remark.

$50-$60/hr of course in NOT what the technician is paid. :(

It SOUNDS obscene unless you try to work up a business plan where YOU have to pay off the loan on the building, make the electric and gas payments, pay the insurance carrier! At that point you figure out what you have to charge to keep the doors open and keep your family fed and happy, and it dawns on you; $50-60/hr isn't quite enough for you to live the American Dream.

I wonder what hourly rates MB Autowerks will have to charge to make it a thriving enterprise?

Sorry for being off-topic and I'll get off the box.

BCingU, Jim


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'96 E300D 60k mi (wife's daily ride)
'95 Audi 90 120k mi
'92 GMC Suburban 139k mi
'85 300SD 234k mi (my daily ride)

One nice thing about high shop rates is that I make $50-$60 an hour tax free when I repair my car myself. I refuse to get a car that has the technology beyond my capabilities to repair it.
That's why the old MB Diesels suit me fine.
P E H

P.E.,

I understand exactly what you're saying.

Larry