One problem related to cooling fan has been reported for the 2010 Toyota Prius. The most recently reported issues are listed below.
Took Prius in for coil replacement and was told the cooling fan was failing and there was a leak from the water pump. Coolant level was not to the low point at anytime and was checked and refilled if not full, the temp warning has not come on. I am now being told that a head gasket is blown and that I need a new engine. The car is not even at 200k and has had all routine maintence and recalls completed.