Hi,

Some oddball reasons for overheating when everything in the
system looks good: At idle only overheat, waterpump turns too
slow.....cause is w/p pulley is too large...

Overheat at speed, air is being pushed from engine compartment
around the sides of the radiator and back thru the core. The
air just keeps getting heated and reheated and the coolant gets
cooked.. You slow down to 30 mph or less and the engine cools
down.

Again, these overheat conditions are very uncommon but always
overlooked.