The pump is the easiest thing to check first, also pull the filter if it is wavy then you are getting water in there. But you would also see a loss of coolant which you did not state was happening.
Also the inside of the clutch cover is another area to look for the milkshake effect. I think..it is one of those spots.
DSM8 - A different kind of mean
SQL > SELECT finger FROM hand WHERE id=3