I haven't taken it apart to see exactly what the problem is, but its
four years old. A full year out of warranty.

An hour or so ago it started making an awful racket. It sounded
suspiciously like it threw a rod. I shut it down along with all the
machines dependent on it.

Diagnostic step one. I looked at the oil sight glass, and it showed
just below center. Figuring to see how much of its guts poured out I
cut the top off a soda can to catch the oil and pulled the plug.
Nothing came out.

As one of our members would say... Blink!!! Blink!!!

I looked at the sight glass again. The oil level looked the same. I
stuck an air nozzle in the drain hole (turned off the compressor, but
left the valve open) and blew thinking maybe it was plugged. A very
little oil came out and several chunks of metal.

I check the sight glass almost every day when I start up the air for the
shop. It never changed. I wonder how long it was running with
virtually no oil.

Well, I'm off to buy a new pump for it. I can't run without air.