Okay so for a while now my car (1991 Camaro Rs v6) has been running quite hot to about 3/4 and then lowers. Im in the process of buying a new thermostat, because I suspect this to be the problem, but lately I've been having a weird sympton. The car seems to run out of coolant quick but the radiator remains full. The other day i was driving at night and stopped and I could see a bit of smoke going out the hood so i checked my temperature and it said it was half way. I popped the hood and it didnt seem to be really smoky so idk. Should I just replace thermostat or could it be something else. Ive checked for leaks btw

 

use a cooling system pressure tester. call/check at your local parts store to see if they rent one, should be one close to you that does. you should be able to find the leak when its under pressure.

 

you are losing coolant but the rad is full? are you going by the reservior? check the rubber hoses for any white or green scale or gunk on them. thats usually a good sign of where the hose will burst