Hello there, is the fan sensor (on the radiater) that has recently been
changed,  a sensor for a 2.1, or a 1.9? They are different, with pre set
points where the fan is switched on. Both have the same threads to screw
into the radiater.The 2.1 comes on earlier by about 6 or 7 degrees, I
believe. The Bently has the exact difference.Is your ignition timing
correct? This can cause excess heat.Correct spark plugs? Catalytic
converter that is plugged a bit can cause overheating. What was the reason
for engine replacement? Was it running very very rich? Perhaps the old
engine spewed out some  particulate crud  that got caught in the
converter.Put your hand infront of the tail pipe and check for even
pulsations or puffs of exhaust. A plugged catalytic converter has a steady
stream of exhaust that just seems to ooze out of the tail pipe. This can be
difficult to determin sometimes unless the plug is bad.