Quote Originally Posted by diagnosticator View Post
This is why I am using only OEM coolant pumps from the dealer. The plastic impeller fitted to OEM coolant pumps is not an issue in comparison, since a cracked impeller won't wreck the engine. A seized pump bearing will grenade the head.

BTW, Re: Prior posts, the coolant properties used in the cooling system has no effect on the pump bearing durability. The pump bearing is not exposed to the coolant in the system.

Quite a few performance tuning shops here in the UK won't sell the metal impeller for this and other reasons. I was chasing a MI pump for weeks and kept getting turned away.

From Al Brown at Awesome GTI (034 Europe Distributor)

"We don’t offer Metal Impeller water pumps as the bearings on them are not capable of staying sealed.
In the past when we have used them they have always leaked. "