[Bill Spain]

Jac Mac sounds like you figured out my problem. It's not the thermostat bypass hose that is blowing up but the rubber cap clamped to the lower heater fitting. The rubber cap does not look very substantial, but I never expected that it would blow if everything else was operating properly. I thought it might be the wrong radiator cap. Anyone want to suggest what I should be running for a cap? I have read everything from 12# to 16#. I also read that Stant is the best.

First thing I will do is remove the water pump and install a plug. Jac Mac from your post, I assume the pressed in fitting will come out and I can tap the hole for a 1/4" npt plug?

Vettestr I will also perform the test you recommended to see if my expansion tank is installed properly.

Thanks everyone!