2003 T & C Weird heating problem

[Crazygirl]

A few weeks ago, after discovering the floorboard of my van wet, my husband replaced the heater core in my 2003 T & C, 3.3 liter Flex Fuel. Everything seemed to be ok, then it started getting cooler out, requiring me to use the heat/defrost a little.
When I first start my van, I can hear sound like water rushing into a container behind my steering/dash. My hubby said not to worry about it. In the last week, when I tried to use the heat, the air would start to come out warm, but turn cool and then go back and forth while I drive. My hubby figured at first it was the cheap radiator cap and replaced it, adding more coolant since it was low.
However, the heat/no heat game continued, so he figured it must be a small leak, dumped some radiator stop-leak in, added more coolant, and the heat seemed to work like it should.
Well, today it seems my van is possessed. Not only is it back to the hot/cold/hot/cold thing, but when I parked the van in the garage, before I turned off the engine, I heard a strange sound, like something small trying to scratch its way out of my steering column. I turned off the radio and listened. The sound kept getting louder, and jointly sounded like an animal clawing around and moving liquid, all behind my dash. I turned off the heater entirely, but as long as the engine is on, it is making that odd sound. I am worried that the heater core may be completely toast, even though we just replaced it, but the floorboard is dry.
I am getting ready to have very expensive surgery, so I really can't afford to put it in a shop and have it looked at, so I'm hoping that someone on here can either offer a solution, or recommend a good priest in my neighborhood to perform an exorcism. Thank you.

[jpb53]

Sound like there is air trapped in the system. You may have to take a heater hose loose at the firewall and refill the system. Another way is to remove the coolant temp sensor and fill; the trapped air needs to be forced out.

[Crazygirl]

I'll have hubby take a look. Thank you very much!