84 300DT with 203,000 km.

My daily driver starts, idles and runs fine. I had an Indy do a valve adjustment about 24,000 km. ago. The maintenance manual recommend to do a valve adjustment every 24,000 km. - should I do it by the book? Or can it wait for awhile? What are some of the symptoms that would indicate an overdue valve adjustment?

I plan to DIY the next time, after reading many threads about it here, but haven't got around to acquiring the special tools (i.e., bent 14" open wrenches and spring holder) required to make the job easier.

Thank you for your time.

84W123DT,

24,000 KM may be appropriate for new engines but for older engines with more miles on them. I have found that every 25,000 miles is sufficient.

I say this because once I was going to adjust the valves of my 300SD after 25,000 miles and NONE of them needed adjustment. They were all with in specificaion. Always check the clearance before loosening anything. You may find that your valves are similar and don't need adjustment or only a couple of valves need adjustment.

You don't need the special wrenches either. I get along fine with 2 open end wrenches.

Most important part of the job is to get the lock nuts on the valves very tight. I destroyed one MB engine because the lock nut (adjustment done by someone else) came loose.

P E H

Several problems with PEH's thinking...
All cars are different. He does not know what settings that indy used....and neither do you... We don't know how often or well you change oil, etc... If you ever have the valve train apart...like to install valve stem seals.... it is recommended to put new adjusting nuts and lock nuts on.... and rotators also... small things can dramatically lengthen the service life of your engine...and the ease of maintenance...
Is it really worth taking a chance on burning an exhaust valve... rather than getting your "_____ " in gear and acquiring the tools and knowledge to do it yourself ?

While you're in there, it's a fine time to check the valve timing (elongation of the timing chain.) Even if the result doesn't indicate that remedial action is needed, it's good to know the number, and to have it noted somewhere so that you have something to which you can compare the next time you check it.


-- eskimo

As Leathermang suggests, it depends on how you maintain and drive the car, MB's recommendation is for every 15000Km is conservative but safe and gives you the opportunity to check other things under your valve cover too. Diesels and especially low powered ones like the MB OM 603/616/617 have to be driven really hard to keep up with the traffic so it is a very good idea to check the valves at the specified interval.

Leather,

Now I have to answer you. I ignored your last comment that I should rebuild 2 calipers when only was stuck because it was so ridiculous.

Replace the lock and acorn nuts on the valves? Why not replace all the valves too and the cam followers and the cam? Why not the whole head. It would make about as much sense.

What does it matter what settings the indy used. That was then and this is now. He either adjusted the valves correctly or not. If he did it incorrectly, he should not be allowed to work on the car again, but how do you know unless you check the clearances immediately after he set them. So you check the valves clearance now and if any are not to spec, you readjust them.

Oil changes or type oil don't have much effect on valve adjustment or valve seat wear. The clearance changes because the valve pounds into the seat and the clearances almost always decreases. If it was wear in the valve train, the clearance would increase.

One of the reasons I have MB Diesels is for less maintenance and part replacement. I don't believe in fixing anything that isn't broken or doing maintanance more often than it is needed.

When I find that none of the valves in my engine needed adjustment after 25,000 miles it proved that to me that adjustments every 25,000 miles are sufficient.

So Leather, you have several problems with your thinking.

83W123DT,

I forgot to answer your question about a symptom of valve clearance less than nominal: Usually hard starting because the valves tend leak and reduce compression pressure. This causes a lower temperature in the cylinder and pre-chamber which makes the spontaneous ignition of the fuel more difficult. The problem is aggravated when starting because of the lower speed of the engine and the colder cylinder head, cylinder walls, pre-chambers and pistons.

And the other guys didn't tell you to check the tightness of the timing chain when you have the valve cover off. Its possible the chain tensioner is not keeping the chain tight enough and it could jump a tooth which really causes problems when the valves hit the pistons.

P E H