Hi, I wonder if anyone can help, I have purchased a used 451 with 4500 miles on the clock, when I start it it will immediately throw water out of the header tank when the cap is off or after about 4 minutes with the cap on.It pump air into the cooling system constantly I have bled the system at the cylinder head many times. With the hose disconnected it will throw the water out and start steaming after 3 seconds which suggests that the cylinder head gasket has failed but there is no water in the oil and I left the car for 2 week with pressure in the system and it was still up to pressure on my return. I have done a compression test on the engine (the battery is a little lazy) cylinders or as follows 1 131psi 2 122psi 3 130psi. the only conclusion that I can arrive at is that the explosive gasses are enough to blow past the head gasket and pressurize the cooling system but the cylinder head clamping force is just enough to stop the water getting into the oil. ps the car runs fine although stationary no misfires etc. Any thoughts welcome cheers john.