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1985 300TD
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Discussion Starter · #1 ·
So I recently came into my 300TD at the end of the previous year after tantalizing myself about owning one of the "immortal diesels", and immediately set upon upkeeping it, oil change, fluid exchanges, filter replacements, etc, and thus adjusting valve lash. In my enthusiasm and eagerness I measured 0.10mm for intakes and 0.35mm for the exhaust, but i incidentally measured between the tip of the rocker arm and valve set nut, rather than the the lobe of the cam and the rocker arm. Oops 馃槵. Has anyone goofed in this way before? I wanted to check with others if they had ever done something similar and whether or not it was "okay" after the fact. In my logic, given the rocker arm is pressed up either
against the cam or the valve itself, the clearance should be the same either way? I was used to measuring lash between the valve and arm vs. the arm and cam which is why i accidentally followed my mental muscle memory before double checking online, then seeing the arrow pointing to the cam lobe and arm lol. Before I go rip off my valve cover and grab my feelers and bent 14mm wrenches, hopefully someone may shed a little light. Thank you for any input, and a happy new year to all.
 

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1985 300CD, 1985.5 Porsche 944, 1969 Triumph TR6, 1998 Land Rover Discovery I, 1992 Volvo 240
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I have not experienced this myself, but given the cost of if something does go wrong, I would be inclined to take the valve cover off again and reset the clearances the way the factory says they should be set. Not all that hard, just time consuming and frustrating when you felt you had done this once already. Better safe than sorry.
 
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W123 300CD, W123 300TD, W202 C250D Turbo
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given the cost of if something does go wrong
Agree 1000%

inclined to take the valve cover off again and reset the clearances the way the factory says they should be set.
I doubt your technique set the clearances within correct to tolerances. These engines will run OK with poorly set clearances but so much better properly set - frustrating but it will be worth redoing them.
 

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1984 300D
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About former owners. Some never knew the valves needed to be adjusted. Some knew they needed adjustments but could not do it themselves and never paid anyone to do it.

Sort of good news. After the first valve adjustment people have said to drive several hundred miles and do a re-adjustment. The reason for this is that that after the first adjustment the deposits that were previously there get sort of worn off and your clearances may change.
 

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European 1974 350SLC ,'78 300CD& '80 300CD sold , '81 240D SWMBO's Car '84 300CD & Euro
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Yep ;

Always re check / adjust them after 500 miles, then they'll settle in and only need checking every 10,000 miles or year .

I was gabbing with an old buddy who's a factory trained M-B Mechanic, he said 'Nate, I believe it's time to do the valves again' so I did this morning (engine stone cold of course) and Lo ! . #4 intake valve was too loose and #4 exhaust valve was slightly too tight .
 

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1984 300D
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I have another one for you. One of the members on another forum has that on the Mercedes Engines with valve rotators the position that the rotator happens to be in can interfere with the accurate adjustment.

I believe he said once adjusted get something on the rocker arm so that you can push the valve up and down and get it to rotate and recheck the valve clearance.

The idea seems to be that wherever the rotated valve ends up with the clearance the widest/loosest is where you do your adjustment.
 

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European 1974 350SLC ,'78 300CD& '80 300CD sold , '81 240D SWMBO's Car '84 300CD & Euro
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?? This must be on some newer engine than I'm familiar with .

The valves always rotate, that's why the tappet doesn't hit the valve stem dead center = it forces the valve to rotate a fraction each time it opens....
 

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1984 300D
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Registered
1984 300D
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5,659 Posts

Registered
European 1974 350SLC ,'78 300CD& '80 300CD sold , '81 240D SWMBO's Car '84 300CD & Euro
Joined
831 Posts
Thank you ! .
 
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