While changing fluid and filter in my 90 LX 5.0 I found a small 1.5" long plunger mechanism. It is plastic or neopreme and mushroom shaped with an o-ring around the slotted circumference of mushroom head. The "stem" of the mushroom is about 1" long and is about 1/8" in diameter. The head of the mushroom is about 1/2" in diameter. Anybody know what it is, what it does and where it goes? When I found it in the pan, I stopped work and have not removed the filter yet. Thanks!