Hi,

I'm new to the forum and as usual with most automotive forums, glad it exists. I've tried to do a decent amount of searching on the threads to get my answers but thought it'd be easier to just ask a few questions and get some feedback.

So, here's the background: own a 82 300TDT with 270k miles on it. Purchased it two years ago. Ran decent with no really nailing or loud engine knocking to speak of. I had to run to Riverside, CA to pick up some cycling parts for a repair and thought I'd take Bru (Brunhilde, to be exact) for a nice cruise from Long Beach, CA. It was a low-90's day but the water temps never went above the usual, and I kept the engine speed below 70mph. By the time I arrived I very loud nailing noise was occurring. At idle it sounds like a carpenter's steel hammer hitting the inside of the engine head once every 1/2 second.

I was going to record a video but now have found that @jarod has had a very similar issue Some ideas on a OM617 Knocking/Tapping/Nailing?. Here is his video of the noise which is the same as our car http://http://www.youtube.com/watch?v=zzLLIDDYk4o&feature=youtu.be

After the noise started (and prior to finding Jarod's post) I took did a valve adjustment (all were decently within spec) and overhauled the injectors with new nozzles. This didn't fix the issue so took to my local diesel Merc mechanic and he did a leak down test. He said it was Cyl 2's exhaust valve burnt and it would need valve job, recommend new valves across the board if one is getting replaced. So we did that and I had him do the timing chain and parts since he was in there. After all that, sound was still there. His explanation was piston rings had worn the cylinder walls . . . which sounded suspicious to me. We've since moved so I've done some more home-investigation myself....so I decided to do a compression test. Prior to installing the tester i checked all the prechambers for missing prechamber balls but they're all there...phew.

Here's the results of a cold compression test (will do warm test tomorrow):

Cyl 1 = 295 // Cyl 2 = 265 // Cyl 3 = 305 // Cyl 4 = 295 // Cyl 5 = 305

Here's my questions:

1. Do those numbers look (especially Cyl 2) or seem to indicate a worn cylinder that could be slapping against the walls?

2. The noise came about suddenly after the drive on the freeway and so if it is a similar issues to Jaron's with a worn cam lobe, does it make sense for the lobe to wear and cause that noise so quickly? I would expect it to slowly get louder and louder unless there was a severe lack of oil dispersion, which leads me to ask, should I be looking for oil dispersion issue up near the valve cover (no the valve cover was not leaking oil nor was any other area leaking oil).

3. Based on Jarod's post, I'm assuming the cause of the noise is the cam lobe slapping the follower and making that noise. It it possible to adjust the interface so that noise is less?

4. If no adjustment can be made, what sort of damage can occur if we continuue to drive the car as is? Would it only damage parts that would initially be replaced when replacing the cam, or could I also cause damage to other parts that would then require additional costs? I'm only thinking of driving it for another 3-6 months to save some extra cash after spending a healthy amount on the valve job and timing chain.

Thanks for the feedback.