All mine leak.I've got the HT131, same problem here, I think it has a manufacturing/engineering flaw. I even had the saw head replaced, about 8 months later....leaking again. It has been to the dealer 4 times now, still leaking.
I guess I am gonna tear into myself. Just wondering if anybody else has had these type of problems, or if we are the only two? Be nice if I could find a schematic drawing for the head. The dealer did also put some silicone on it, as Erick suggested, started leaking again.