I think he's talking about the top of the tube, where the 152 dipstick screws in. Borrow another dipstick, and see if it still does it. It is common for people to overtighten these, and eventually the threads on the dipstick become worn. Your dipstick should be snug, but not "torgued" on! The 'o' ring, if in good condition, is all that is needed to secure and seal the dipstick, without over tightening it after it bottoms out.
Carl
