l just had my water pump replaced thinking that was the problem but it turned out it wasn't. it will get really warm (about 3/4 on the temp gauge) but when l hit the gas and start moving again it cools right back down to the normal running temp...what might be the problem?

You can check your fan to make sure the clutch is working properly, also double check the coolant level. If all else fails maybe toss in a thermostat.

Sounds like ur thermastat is stuck in the closed of almost closed position . Change it . Also check ur Rad. cap most any parts house will do it for free.It is posable that u have a poor fan clutch but not likley. with the eng. off. Check for any loose play it should turn but with some resitents . Rad. could be trying to clog up on u also. Is the water cirulating good when u have the cap off? l t wo not till it warms up. also ck.the water level. If all this checks good then u got a bad W/P. That makes up the cooling system of ur veh.

Sounds like bad fan clutch

Could be;Bad vacuum advance,improperly timed,vacuum leaks,air dam missing under the bumper,fan clutch could be bad.