Is the head gasket bad? or WHAT?

I am a bit perplexed. We have a 94 with the v6 3100. It has a sealed coolant system. NO radiator cap, just the expansion tank. The car was Boiling over at under 220 when the fan would turn on. We replaced the pressure cap. We replaced the thermostat. Originally it had a leaky radiator and truly overheated to just steam in the system. We replaced that. After replacing the cap it started overpressurizing. The only way to get it home was to leave the bleeder open and air would continually come out of it (along with coolant) This was a 50 mile trip. So we filled the system completely up with water and watched bubbles coming out of the expansion tank (cap off) at a very even put put FOR OVER HALF AN HOUR. And it smelled like exhaust. We thought and thought and the only thing we could come up with was a break in the head gasket between water port and cylander. So there is is all torn apart and there is no break in either head gasket. ANY ideas?

My dad's Oldsmobile was doing something similar to this...his hoses would swell up with pressure from the engine....and while the head gasket looked poor he had a cracked head, very common problem. We had this on our 91 Corsica as well now that I think about it, some years ago. Since you have the heads off take them to a machine shop and have them tested. They will have to take the valves out to so this right as you can have a crack under them as well(my dad's was this way). If they check out them not sure what else to check if you are sure about the gaskets.

Sounds like head gasket, or cracked, or warped head. Either way you need to take the head off.

While the heads off take a flashlight and lay it flat on the block look closely for cracks between the pistons.
As recommended get the head pressure tested. Also have them put a straight edge on it for you.

We had the heads done and no cracks or warp. There was one bolt when we removed the head that had nearly no torque on it and it was rusty. The gasket had a clean area and the guy pointed out that there was no carbon build up around the edge of the cylinder or around the valve area on the head. So it looks like there was a gap caused by a bolt not being torqued correctly. The guy says that could cause it and he recomended using a liberal amount of coppercoat on the surfaces when we put the heads back on. So hopefully riddle is solved. Tahnks for the input. And wish me luck.
Nancy