So we bought a 98 EX from my dad's friend from a car shop. After a few days of driving, engine overheats and coolant evaporates quick (less than a week and continues for about a month until I brought it in) so I'm forced to refill. The engine reads hot at idle sometimes and sometimes during drive and also when I reverse(:: shrugs:. So we brought it back to the shop/mechanic from which we bought it from since he said if there's any problems just bring it back and he'll get it fixed if's its within 6 months of the car transaction and what not. He says it was the thermostat/sensor so he fixed (maybe but i doubt it) and even placed it with a whole new rad. This solved the problem for about a month or so and this is why I'm here.

So the engine reads hot after only about 5 mins of driving/engine startup is hesitant as if it starves for gas/horrible mileage (23-25mpgish)/intake filter is rusted/and all other kinds of problems that I don't have time to tend to or knowledge of well some very little...just no time.

So last night after a drive to a friend's house engine was hot like it has been starting 2-3 days ago. I turned the engine off thinkin that I would be at the house for awhile but wasn't and upon startin the car...car starts and sounds/feels if the engine was knockin makin a thud thud thud thud sound and excessive of white smoke coming from the exhaust. Turned it off left it there and came back a few hours later and car started fine with the exception of reading hot about 5-10 mins later upon driving.

Any idea what could be the problem...or well problems?
I plan to bring it back to the guy today or tomorrow, but was wondering if yall would happen to make any specific judgements.