If the vehicle has electric cooling fans, do they turn on? Could use more info like year, make and model.
Is your fan coming on?
Either the water pump impeller is loose on it's shaft, or you have a leaking head gasket.
Year, make and model would help us help you.
brilliant, the thermostat is backwards
Sell It!!!!!
possiable head gasket
Inoperative radiator fans, bad water pump, failed headgasket?
have a blown head gasket is my guess
fan clutch?
if it's like my V8 Porsche 914, i had air pockets in the cooling system at the water pump. when air is at the water pump there is nothing to push water. Therefore overheating. Other things to check is water pump and radiator.
its either the water pump or thermostat take it to a shop if you can that pump is a nightmare to change
Has the rad ever been flushed? Try that if there is no indication of water pump failure (leaking or venting coolant from pump.)