my 1986 isuzu p'up diesel has a hose with a plug hose clamped in the end of it that sticks up from where the oil filter is screwed in. I was driving along when I heard a pop and and pulled over to see that the plug had shot off. I put the plug back in and hose clamped it, added some oil and started it back up. I pulled over after about a mile to check on it and saw that the hose had swelled up around the plug, but the plug stayed in all the way to my house. What could cause the build up of pressure?