my 86 prelude's temperature gauage running high. it always over half after drive around little bit longer. but i never reach the redline. is that mean my radiator going bad? i open the air conditioning everytime i drive, but i don't open with AC. will that help cool down my engine?

 

you have plenty of coolant? and did you recently change it?

 

Does the temp gauge fluxuate alot? Like slowly rise up over the middle line, and then go back down? I had the same problem, it was a bad thermostat. I would change your thermastat if it hasn't been done after a few years, just don't let honda do it or they will charge up the ass.

 

my coolant was ok. and i haven't change it.
yah, it is kinda rise up to the middle first, then it continue rise to over 3/4. then if i open the fan, it will drop a little bit

 

yeah...id try a thermostat

and make sure your cooling fan is kicking on

 

yah check cooling fan operation, drain and flush the radiator, install new thermostat, and check all hoses while ur at it. running the stock engine u shouldnt need to change out ur radiator unless its leaking.

 

Check your ground wires, those can make your needles do weird things.