It may sound stupid but is your belt wrapped around the front or the back side of the water pump pulley. It should wrap around the front. YES it is possible to put it on with the right belt and everything work properly but the water pump will spin backwards and basically cavitate the coolant and it wont flow properly, plus the thermostat will act like a damn and make things worse when its flowing backwards. Just a thought I have heard of this before. Repeat engine grenades sounds like installed error.
