What, exactly, is "Nailing"? I know that it refers to an engine noise being emitted by a diesel engine in need of a repair, but what type of repair? How do I recognize the sound of Nailing?

I heard this term by bus mechanics referring to a diesel bus engine making some sort of noise.

If you search for "nailing" in topics, you will find 17 threads that have "naiiling" in the subject line. Many are very informative.

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1977 Mercedes 240D. 4-speed transmission. Windows, A/C, and sunroof: all manual. Medium Red. 204K miles.
1988 Subaru GL wagon. Dual range 5-speed 4X4. Daily driver w/ twin parts car.
1994 Subaru Loyale wagon. 5-speed 4x4
1966 International 3/4 ton 4X4 truck. Ooh yeah!
1952 Ferguson TO-35 farm tractor.
1984 Snapper rear engine riding mower. Just like Forest Gump.
1988 Nimble 20 sail boat
--Older stuff is built better--