ok im only gonna say this because i just dealt with the same problem.... i changed my radiator, all the hoses, thermostat 5x, straight wired the fan to a switch, flushed it 4x, new waterpump, ect..... and it was the head gasket even though no smoke, perfect compression, no coolant in oil, vice versa, head gasket would be the way to go... i spent $250+ on a $25 problem... good luck