Almost 100% an air pocket

happened to me the first time - I think it "geysers" when there is air in the block and the thermostat opens, shooting hot/expanding air into the radiator and out through the rad cap.

All my previous cars had bleeder valves which made bleeding the system easier, but I have always just put the front it up on blocks and let gravity do its thing

 

I don't know what else it could be but a crack. I will start pulling it tomorrow.
Thanks

 

I hate to do the same job twice , did you do a block check ?
first thing I do , anytime I work on a customers veh, is "verify the complaint" .

 

Looks like a great tool. I cannot run mine more than 5-6 minutes and then all the water has blown out of it.
Thanks

 

Water in the oil ? oil in the water ? If it were me, I would pull the thermostat fill it with water and try it again . if you had everything magnafluxed it should be fine , Good luck buddy .

And all bets would be off if it were a boat, they like to crack everywhere, cold lake water and hot engines don't mix well LOL

 

You elevated the front but did you squeeze the upper radiator hose to get rid of the air pockets? This is done with the engine off and the radiator fill cap open. Squeeze the hose and after you let go you should see bubbles rising up through the radiator filler point.

 

I decided to try to pressurize the cooling system before I pulled the head. I made a home brewed tester and to my amazement it holds pressure. It has a slow leak down of 10-15 min or so

which might be some of my fittings. How long should it have to hold pressure?

 

Another thought. I used an overhaul gasket set for the 2001 4.0 and bought an intake gasket for the 7120 head. I used the head gasket from the 2001 gasket set. Is there a difference in head gaskets from year to year? Should I have bought a head gasket for the 7120 head?