Is it an aluminum ball that's crushed into the conical end of a threaded hole when seated to create a positive seal? Guess you won't know unless you remove the plug and notice it stuck to the plug or receive the new ball. Crushed aluminum ball seals are common for long term positive seals in aerospace applications. And my 1967 Datsun roadster used them in the brake bleeds.
Adding to this possibility, the parts diagram shows no seal gasket on the plug and seems to indicate a dished out plug interior end to accommodate the ball. Was the plug straight threaded as opposed to a tapered (sealing) thread.
Adding to this possibility, the parts diagram shows no seal gasket on the plug and seems to indicate a dished out plug interior end to accommodate the ball. Was the plug straight threaded as opposed to a tapered (sealing) thread.
