Okay, but after replacing the thermostat, and connecting the lower radiator hose, disconnect the upper radiator hose at the radiator, fill with coolant till it takes no more, reconnect hose to radiator, fill radiator till it takes no more, remove burping valve on top of radiator located oposite to the filler cap, pour coolant into little hole until it takes no more. Oh yeah, do all of this with the heater temperature controller on your dash turned to the high temp side. Do all of this before starting engine. Also, since your brother just changed the timing belt, make sure he didn't disconnect the radiator fan control wires and forget to reconnect them
This worked for me after swapping a 2.5l engine.
James