[scottj]

Jim,

If I understand you correctly, your filler adaptor on the intake has the cap on it with a line to the overflow tank? If this is the case, your problem is the cap location. The cap should be at the highest point in the system but on the low pressure side.

At the highest point in my system I have a surge tank with a radiator cap on it. I have a -10 plumbing the bottom of the surge tank to the suction side of the water pump. A -06 line is plumbed from the upper corner of the low pressure side of the radiator to the side of the surge tank. The surge tank is approximately 1qt capacity and when cold it is 1/2 water and 1/2 air space. Plumbed this way the surge tank will have a constant, low velocity flow that will separate any air in the system and expel it should system pressure exceed the cap rating. My system maintains a constant level and doesn't require an overflow tank.

The problem with a cap on the high pressure side of the system, such as above the thermostat housing or in the upper hose, is that water pump pressure will push coolant past the cap regardless of system pressure or coolant level. This could have serious consequences on the track and should be corrected.

Scott