85 SE Oil Cooler Question
 

Picked up a nice used O.E. oil cooler for my 85 GSL-SE. I hear what sounds like a ball bearing moving around when I lift it up left and right. It's specific to that movement. It also sounds pretty consistent and not like miscellaneous trash moving around inside. Anyone have any idea what this may be and is this normal? I know there is some sort of pressure valve inside but I've never had the correct cooler for my car so I wouldn't know if it's normal.