My wife's 99 accord has a problem. The temp gauge goes high after driving for a while when you slow down and then drops back to normal (about 1/3 of the way from C to H) after you pick up to driving normal speeds. It overheated about a month or two ago and we had the radiator replaced with a new one (old one was cracked) and we didn't notice anything until last night when we were returning from a long trip. If it helps any that gauge was doing the same thing before the radiator was replaced. It doesn't go up slowly as one might expect, as soon as you slow down it starts bouncing up quickly and then back down then back up to near the "H". I'm new here and any advice would be appreciated.

Thanks, Charlie

 

Check the coolant level....bleed the system.

If the level is low, find the leak.