1980 300SD Turbo.

Symptoms:

Tapping sound started about 150 miles ago. Quietly at first, but then got louder--like a loose valve sound. It sounds similar to a Cummings V-8 diesel--loud....

Idles a little rougher than it used to, starts with no problem though.

Slight increase in black smoke under acceleration but disappears quickly.

Took valve cover off, adjusted valves--no difference--sound still there.

Replace injectors--no difference.

What next? Any ideas?

I'm going to check valves again this morning, but I'm pretty sure they are correct.

As an aside and unless I made a mistake--and this may have nothing to do with anything--my mileage went from 26 mpg to 31 mpg.

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Rev. Dr. G. Church of the SubGenius
It doesn't take a genius

mileage could be just due to the #2 fuel being available again.
noise could be tons of things, try to isolate it with a broomstick against your ear, or a short length of garden hose, to use as a stethoscope. when you had the injectors out, did you look at the prechambers? are all the atomization globes still in place?
hopefully, it's not a rod bearing or something. has your oil pressure ever dropped below 1 Bar, or 15psi? have you ever run it out of oil? is there oil in the sump? where is it on the dipstick? bottom mark? top mark? above the top mark?
John

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John HAUL AWAY, OR CRUSHED CARS!!! HELP ME keep the cars out of the crusher! A/C Thread
"as I ride with my a/c on... I have fond memories of sweaty oily saturdays and spewing R12 into the air. THANKS for all you do!

My drivers:
1987 190D 2.5Turbo
1987 190D 2.5Turbo
1987 190D 2.5-5SPEED!!!

1987 300TD
1987 300TD
1994GMC 2500 6.5Turbo truck... I had to put the ladder somewhere!

1980 300SD

It uses very little if any oil--and what it does lose is through the oil cooler having a slight leak. I might put a half a quart in it (if that) between 5000 mile oil changes.

I didn't look inside the injectors, but I'm going to bite the bullet and go out and pull the valve cover in a minute and re-check the clearance.

I appreciate any ideas.

__________________
Rev. Dr. G. Church of the SubGenius
It doesn't take a genius

BTW, never run out of oil, oil pressure idles at 1.5 to 2, pegs at normal speeds and when cold.

__________________
Rev. Dr. G. Church of the SubGenius
It doesn't take a genius