changed the thermostat. it overheats but cools down a heat bar or two idling at stoplights. i filled up the coolant reservoir when i changed the thermostat, drove it about 2 miles(engine was already up to temp when i started) and it overheated. drove it two miles back going about 35-40 and it never went above normal but was still overheating. checked the reservoir and it was empty. stuffed a hose in it and plugged it up with a towel to force water in to see if it was leaking anywhere, no leaks. while running with the rpms up the top hose is easy to squeeze. makes me think water pump. but if i go over 45 it over heats makes me think clutch fan.
it's a simple little part, a pain to fix. Head gaskets
well if it is the water pump you will have a small hole ( tale tale hole ) and it will be leaking water to let you know its out. and clutch fan there will be alot of play i have seen people stop them with there hand but i dont advise it
So if i understand, you are losing water from your system but no evidence of where it is going. I can think of two options. Heater core, but you may get a coolant smell inside the car, steam on the interior of windshield. You can check this by connecting the heater hoses directly, bypassing the heater core. If it still loses water, look for foamy oil on the dipstick or on the oil filler cap. If present then the other guy is right - headgasket. I would also look into flushing the system, or replacing the radiator - it may be clogged.
