Hello,
I have an '81 300TD that has been my only car and daily driver since 2009. It has/is totally reliable and in good running shape. I adjusted the valves last year, and again today. After taking the car for test drive I noticed a significant clacking noise once the engine is hot. I don't remember hearing such a noise last year after adjusting the valves (although my memory may not have recorded it.) I adjsuted the valves while the engine was cold (ambient temp was around 80 F) to MB specs of .10mm for Intake and .35mm for exhaust, and per the MB manual the feeler gauge took some minor effort to pull out of the gap. After doing them all I double checked them all to make sure they not only were to spec, but that the feeler gauge felt the same in and out of each lobe/lifter. Is it normal to experience such a clacking noise after making adjustments? It sounds like it may be from one or two valves, not every one. Is this noise likely the valve slapping into its seat, or the cam slapping the rocker? Or the rocker slapping the top of the valve? It seems to happen when the engine is hot. Yes, oil level is where it should be.

 

Did you check the locking nuts were all tight after you adjusted the valves ? None of them were stripped ? Did you leave anything under the valve cover ?
Major disaster happens if one comes loose and the valve drops.
If all is well under the cover then with the engine running, start at the front cylinder NO 1 and slack off the injection line at the injector. Slack and tighten each injection line in turn 1 to 5 If any of them stops the noise suspect the injector in that cylinder has a problem.

 

Yes, I assured that all of the lock nuts were tight and no, there was nothing left under the valve cover.

Also about 2-3 weeks ago I overhauled all injectors, put in new Monark nozzles, and balanced all to 2100 psi +/- 50 psi (the top end of the range designated by MB). There hasn't been any noticeable injector noise since then, and this clack-clack-clack only showed up immediately after I did the valves. That being said, my #2 injector is leaking a little from between the injector halves. I need to pull it out and check it out as soon as I get some extra crush washers. Sometimes the noise is more noticeable than others, but seems to happen more when the engine is hot.

 

With a screwdriver you can pinpoint the noise put the tip against each injector, and over the valves on the valve cover with the handle against your ear. The noise will be the loudest at the point where the problem is. Investigate from there. It sounds to me like one of the valves loosened up, or might have been starting up the lobe when you adjusted it.

 

Can you pinpoint where the clacking is coming from ? Front Rear Center ?
Check with a long screw driver with one end up to you ear or use a piece of rubber hose to your ear.
Just because the injectors are new doesn't exempt them really. Monark are the best ever made, but a pintel can stick. Leaking halves are common after injector service. Need to be taken apart and lapped.
Did you happen to turn the engine backward when you were adjusting the valves ? This can cause timing chain problems. Is the chain tight on both sides of the camshaft sprocket ? The screw driver will help tell if the clacking is in the chain case area's. If its the chain you need to replace it and the tenshioner and the top guides.
Anouther area is the vacuum pump. If that is the area the engine needs to be shut down and not run. The vacuum pump removed for investigation. The drive off the injection pump advance, can be damaged and also parts can fall into the timing chain and sprockets if this falls apart. Does is sound like a metal to metal clacking or a fuel knock ? Try as I said slacking off each injection line in turn. If its a cylinder, that will locate which one it is. The pre-chambers have a ball pin in them that the injection nozzel spays across. If this comes loose or breaks you will get a clacking noise, but more like fuel knock instead or metal to metal.
Funny this should occure after adjusting valves.