It's possible your system is airbound. There's probably trapped air trying to get out, hence forcing the coolant out.
Changed my coolant reservoir today and now im not sure is this ok...
If engine is running coolant level doesent raise with cap on or off, stays at the same level.
If I turn engine off, coolant starts raising till it starts overflowing if the cap is off,after putting cap on I can hear coolant flowing thru that thin hose from engine to coolant reservoir
In both cases engine is at normal working temperature.
Is this how its supposed to be or not?