A ball shaft for a coolant valve includes a body extending from a first end to a second end through an intermediate portion defining an axis of rotation, and a ball section formed on the intermediate portion. The ball section includes an outer surface, an inner surface that forms a coolant receptacle, and a slotted opening extending from the outer surface to the inner surface. The slotted opening includes a width of between about 0.0374″ (0.9499 mm) and about 0.0364″ (0.9246 mm).