[Old Blue 66]

Originally Posted by Old Goat 67

Exactly. When they are flattened, they do not match the curve of the plates and therefore you have whats called cavitation. IE, water flows around the edge much more and is not moved the way it was engineered. IE, volume of water pushed is less and flow through radiator is less. Overheating.

Flattening the plate to match the flat impeller reduces the cavitation, but volume suffers.

Thank you. Now I understand.