Ive got a 99 Honda Prelude 150k miles fully stock - engine was replaced with another stock one.

So, when I come to stop lights it overheats but when Im driving it doesnt....

Fans DO NOT kick on UNLESS A/C is on , but I changed the fan relay 3 months ago ????

And sometimes, it doesnt overheat at stoplights , yesterday it did, today it chose not to.... WTF IS GOING ON !!!!!

 

not sure if this helps but my buddy had same symptoms on his bike. when he was moving it was fine. when he was stopped it would overheat. he set his fan up to be on all the time but it didnt help. he then changed the thermostat but still overheated. turned out to be his water pump went bad.

 

Replace your ECT...Engine Coolant Temperature switch