hello all i have an 91 civic dx good little car but it started overheating after i changed the thermostat and added antifreeze i drained the cooling system and ran the car for a week(app 250 miles) on water alone with an cleaning solution then i drained it changed the" t "stat and ran anouther 100 miles or so on just water all was fine no problems when i added antifreeze ( once again total drain) the car started running hot(almost on the red mark on guage) it will do this on hot days and on cool (45 degree) nights some times when i stop it will cool down some times not. If i shut it off while its in motion coast for a bit when i restart the guage will drop to normal temp i,ve tried 2 new "t" stats and the orignal also i added some stop leak to correct very small leak in the heater core.Any sugestions would be helpful as the car runs great since i got it a year ago and has less than 160.000 on it and i want to keep it it has a problem with the main relay and i want to replace that but i would like to get this sorted out thank u Tony C.

 

water pump maybe... thats all I can think of

 

well it seems the stop leak worked too good i had some plugged tubes in the radiator back flushed it (again) and all is well thank you for your help polo708