Strange intermittant cooling system problems. Help please.

[69eliminator]

I have a 2002 7.3. In the last couple of months it has intermittantly started puking coolant out around the cap all over the passenger side battery. Along with this, the heat only works intermittantly as well. Usually the heat problem corresponds with the puking problem. I have done a number of things to try to fix the issue which I will list now:

New Motorcraft water pump
New Motorcraft radiator cap
New Stant thermostat
Flushed and refilled cooling system
Had a diesel shop run a pressure test on the cooling system. It is not building an unusual amount of pressure and there is no coolant in the oil or vise versa, so I don't think I have a head gasket issue.

I am running out of ideas and was hoping maybe someone on here might have some ideas for me to look at. Any help would be greatly appreciated. Thanks

[NoRalPh]

First thing I would do is to, find somebody with or Buy, a "Block Tester" (that's what mines called, there might be other names) that will take the gases from inside the degas tank and test them for the presents of exhaust gas. It's a inexpensive tester that draws the gases from inside the tank through a liquid that changes color to let you know you've got headgasket trouble. That actually sounds like a likely culprit in your case (hope Not, but I'd eliminate it first )