the O ring is on the cap,. inspect it to make sure it is OK. and do not over tighten it when replacing it, and watch out for the spring in the cap,dont lose it, and when I clean the wire mesh filter I use a needle nose plyers to get it out, gently,. air blow it clean, drain bolt beside it drain and tilt scoot over a little to get last of oil out,. put it together add oil your done,,,..