Yeah, you need that O-ring. If you have an Oreillys near by ask them to see there o-ring assortment behind the counter. They should have a whole tray of o-rings (ask someone thats been there awhile, not some new guy. They will try and take you to the Help isle), match it up. If worse comes to worse HELP makes a box of orings, there MAYBE one your size in there, not sure though. Either way, get an o-ring....