thanks for the info.
these reasons for a over flow bottle to spill over is
the system is over heating.
the radiator cap is bad.(you replaced already)
the engine has a internal combustion chamber leak (blown head gaskets)
a water pump thats not circulating the coolant (bad or rotted impeller)
a sticking thermostat causing the car to over heat.
well their is not any real testing for this.
if you lower the coolant level you should be able to see the coolant flow across the fins.
how many miles on the car ?
ok and this is the original pump on the car ?
if so i would replace it i have not known of one that was not changed and lasted that long.
if the cooling system was not properly kept up with coolant anythings possible
does the cooling system have any rust in it ? or have been kept up ?
this will require the removal of the timing belt.
have you done that belt before your self or a shop ?
i can provide the directions but if your not able to tackle this then it will be best for a shop to perform this.
if the belt gets off time theirs alway a risk of bending valves if the cam belt is not set correctly
please CLICK HERE for timing belt over view
please CLICK HERE for timing belt replacement
please CLICK HERE for water pump replacment
please CLICK HERE for timing belt install