Back at the end of August, while driving my 1990 C4 w/113k and no known engine work, the low oil pressure idiot light came on at a stop light and the pressure gage indicated a lower reading than normal. In the weeks the followed, I replaced the oil pressure sender, changed the oil, had the oil analyzed, and then pulled the pressure relieve valve plug/spring/piston assembly which controls the oil pressure. The piston was in good shape as was the spring and so I reassembled and poured the oil which had drained out while examining the assembly into a spent oil container. In the bottom of the pan I found a small ball of metal (~3/32") which appears to be brass, but which is slightly magnetic (ferrous).
The oil analysis did not show any abnormal results with the exception of 25ppm copper vs. the expected average of 11ppm. Once the oil relief valve was replaced, the oil pressure problem was solved. I am relieved that I was lucky to have a simple fix for a possibly major problem, but I am still concerned. I plan on having another oil analysis done in about 3k miles to check for any trends.
My primary question is what inside of the engine might contribute to forming this metal ball and was it formed at the end of the oil relief piston or is that just where is finally lodged? Does someone have a picture or drawing of how the relief piston works?
--tom