If the cooling system is pressurizing before it reaches normal temperature, you have compression/exhaust leaking into the cooling system. Rent a cooling system pressure test kit and with a cold engine and normal water level, attach the pressure gauge/rad cap. Start it and observe the gauge.
1957 Chevrolet 5700 LCF 283 SM420 2 speed rear, 1955 IH 300U T/A, 1978 Corvette 350 auto, 1978 Yamaha DT175, 1999 Harley Davidson Softail Fat Boy
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