[Green7mgte]

1.. quite topping off your rad.
2. check your rad cap.
3. whats the pressure on your rad cap

if you fill your radiator to full, when it expands itl be forced to dump.
when coolant warms it expands and pressed against the spring in the rad cap which opens it up. faulty cap ='s dump.
Filling the rad up to the top row is fine. when cool there should be about 2 inches or so below the neck.

If your puking green then you are overheating and that's the pressures escape rout.
Id replace the thermostat and the rad cap to be safe. Then give it a good Burping.
help me help you.. Do you have heat?
worse case scenario you have a blocked rad creating a flow restriction exudes in a light overheat. Not seen on the temp gauge but is for the ecu.
best case scenario is you just have a bad rad cap. won't hold pressure and just dumps. check that first man Good Luck