I have hardly driven my car this year, like 2k miles. When I put it away last season it had a few hard track days and a not so great UOA. With 144k miles she still runs strong though and I have enjoyed the times I have had it out this year. The other day I noticed what I was certain sounded like a knock, but never heard it afterwards, even listening closely to the engine a few times I couldn't hear it. Then this a.m. I noticed it again, except more distinct, then it went away. Well tonight I decided to investigate more and took it for a quick spin and brought it back to listen, sure enough "tap, tap, tap", but then nothing. At this point I am hopeful it is a rod bearing caught early as I planned to check the bearings over the winter and replace if needed. But I am growing concerned that it is a thrust washer issue due to how intermittent it is. So I had my wife push the clutch while I held the crank pulley (car off obviously) and I could physically feel it move in my hands, not a ton but I could feel it move outward. The funny thing is that I didn't feel it move back and when she pushed a second time I didn't feel it move that time.

Next I checked the Vtec screen and found a very tiny flake in the top portion and then two rather large objects in the screen. I say objects because I couldn't make out what it was or if it was even metallic, but it appeared quite worn like it had been in there for a while. If it is engine material I would have to call it lead. So I guess with my description how concerned should I be? I am dropping the pan over winter and am done driving it this year, but I don't want to replace rod bearings only to have the thrust fail.

 

I am in for hearing answer on how to diagnose thrust washer issues. I like your test with feeling crank pully while clutch pressed. Good idea. Not sure how much play there, if any, is normal.

The intermittentency of the noises you are hearing, is it making noise when engine is cold, and goes away when warm?

The stuff in the vtec screen, I would think if that was from bottom end, it would have gotten caught by filter. So it must be from somewhere after filter (unless filter was clogged and in bypass mode).

 

Nominal end play is 0.004" to 0.014". That's basically 1 to 4 sheets of paper. HF $35. Dial gauge.
Service limit is 0.018".

 

I am going to say it was certainly greater than "1 sheet in movement" and would be on that upper end for sure. It moved a good bit in my hands. Is there anything to see/check with the pan dropped?

The knock is is just random but seems very much like a knock. Engine noise in general is reduced when I press the clutch, but my tranny is quite noisy with the clutch out, so hard to say if it is engine noise or tranny noise being reduced.

 

Here's an interesting YT clip. With generic engine:

 

The only thing I got from that is maybe I am still good, because that limit is tighter and it seemed like the crank moved a TON compared to mine. I could just feel it clunk forward when the clutch was pressed. I could actually hear it somewhat. Like I said I planned to replace the rod bearings, so if that is my slight knock then no biggie. What I don't want is to replace them to just have the mains be trashed.

 

Generic engine? That there is a cast iron closed deck block from a mid 90's Group B rally engine