Cooling system woes

[kkrover]

I am loosing my patience with my 95 SWB. Have done heads, lifters, rockers, all gaskets, most all hoses, radiator, and t-stat.
Recent history:
Car runs great after top end rebuild, but after about 2 weeks I get waterfall sounds back in dash and coolant level was down a bit. Would top up and waterfall sound would get better. So, then i replace the radiator (was leaking on the sides), with a proline from RoversNorth.
Right away i hear waterfall in dash, but think if i drive it it will force it out. I then park on a steep incline to help flush the air out and it obviously worked b/c the next day expansion tank was empy, and got the mechanic to top it off and they it must have been an air bubble, BUT waterfall noise still present. SO I take it back and leave it for 3 days and they said they worked it out the best they can, and they checked the coolant for Carbon, and no problems there, so must have been a bad air bubble.
The next day I then recheck the level, and it was about a 2 pints low, so I top off and drive 3 hrs to Georgia. The next AM I check it and I couldn't open the cap as coolant was pusing out (engine was stone cold). I was very worried, but drove home anyway..no problems, ran at normal temp the whole way, and I check it this AM and level is perfect. All the while since the new raditor, there are no coolant leaks to be seen or smelled.

3 questions?
1- what would casue the coolant level to surge like that? I assume it is air
2- How can I get ride of the waterfall, sloshing noise once and for all.
3- Where could air be getting in, but no coolant coming out?