Some plastic impellers fail at the shaft and spin, causing the water pump to not move internally. It's rare but it does happen. The metal ones can fail at the bearing but I've never heard of the impeller separating. So they can both fail but if I had a choice, I'd go metal.Hi
My online vendor sent me a Graf water pump with plastic impeller. Has somebody bad experience with this water pump. Shall I exchange for the one with metal impeller.
Thanks for any advice