hopefully you have caught the problem early so minimal damage was done,worse case it's popped the headgasket which is is common on the old zetec motor when pumps or hoses break normally the number three cylinder is the worse hit.

hmm to get round the problem would surgest you fit a swirl pot for the coolant and fit one of ggr temp gauge kit and dash pod not cheap but a very good bit of kit and worth getting to prevent major damage like headgasket failures which £500- £1000 pound
also it might help if you get a coolant with a higher boiling point, reconmend halfords summer/winter coolant red in colour, also check the thermostat for open degree's

hope you get it sorted soon !!!