There’s no oil in the water. Just INSIDE the housing. The seal is in great condition & should go back together fine. The intent is to see if I can put in a more reliable cap.
I have lots of experience with air-tight and also gas (natural and propane) tight. Plus some experience with submersible pumps. So long as corrosion / deterioration of surfaces / materials is not a problem (they look great), water tight is much easier. The oddities with the motor cap are a bit new to me though. Usually the failures are more obvious / drastic.
That said, I’ll set the reassembled pump in several feet of water for several days & then put it in a large bucket & test it. Moisture inside should trip the GFCI outlet.
I’m going to get a new pump anyway. But I suspect “skimping” on the caps happens on all but the most pricey. Motor caps seem to fail often. This is more of an engineering project to see if I can improve the thing, and will give me a backup.....
(Yeah, there’s already a “battery backup” pump installed, too.)
If you are having caps fail on a regular basis on the same motor you need to investigate the power quality of the circuit that supplies the power to it. AND run a megger on the motor.