I had a basement sewage pump installed 6 years ago. In the past few months I've noticed an odor. Do these units require maintenance? Could the odor be coming from the top of the unit around the seal? Could I use caulking around the top seal to prevent odor or might this cause a problem?

Check the seal on the cover and see if it's tightened all the way down and replace if necessary. For a temporary repair you can caulk around the top seal but you really should replace the it. Good luck, Tom