how do i check the source of my car's overheat problem, its a chevy optra... here: the temperature rises up to almost 3/4 or even higher of the temp gauge... even with a bit short distances. it is gulping water every trip. it just happened a couple of days ago, both fans (auxiliary and radiator) working, replaced the auxiliary fan lately, and the thermostat... there is extreme steam pressure in the upper radiator, its hotter than the other hose, based from my touch, (this is where the thermostat is located), a day ago, there was steam coming out of the radiator reserve cap, replaced the cap now its ok, when i replaced the aux fan yesterday i removed and returned the upper rad hose connecting to the radiator, and clamped it, perhaps the clamp is not sealed enough as of today i can feel the steam pressure escaping from the hose that is connected to the radiator, might come back to the mechanic who put them yesteday to tighten the clamp... but i am not sure if that solves it, because there is still the overheat problem to think of,. how do i solve it...

the rad months ago was replaced along with the aux fan and thermostat not more than 3 months ago, with chevy service center, if it continues heating the engine it might destroy the engine so i wanna pinpoint the problem.. and diagnose it correctly, i dont like the idea of replacing everything, just to make it work... if one can diagnose where is the source, well be answering the problem right on..