I have had my space saver for just over a year and the following has just started to occur: I noticed there was not any oil in the sight tube so I filled it up and as I ran the pump, I could not keep oil in the sight tube. I cannot see any external leaks. I noticed that bubbles will come up through the oil in the sight glass every once in awhile. What do you think the problem is? Any advice would be appreciated. Thanks!