Just reading through the posts and it looks to me that it has a blown head gasket. What appears to be "boiling over" and spilling out its coolant is actually caused by escaping combustion gasses through a leaking head gasket. This causes more pressure than normal in the cooling system to build up and push the rad cap spring open, causing it to look as if it is boiling over. Bubbles in the reservoir are not caused by boiling coolant, they are combustion gasses. This is the cause of bubbling and gurgling sounds you can hear after you shut the engine off. The reason the fan don't run when it is "boiling over" is because the boiling isn't caused by the engine overheating, it is gas bubbles injected into the cooling system. When the coolant gets low enough, it will then cause the engine to actually overheat. A leak down test of the cooling system is not 100% fool proof. If it has a severly blown gasket, it will show a bleed down over time. Remember this the 10 or 20 PSI of pressure placed in the cooling system may not leak through the gasket, but the 1000 Psi plus from combustion pressures will certainly leak out! I had the exact same problem with my 3VZ-FE five years ago. I since bought two more that had the exact same symptoms, caused by blown head gaskets. Look no further, this is the answer. Good luck!