Does anyone know alot about ford fiesta coolant systems?

whats the problem?

my coolant is leaking but there is no obvious signs of leakage e.g. no pools of water on the floor. and the oil is fine, no whitening around the cap, all vales seem secure and cant see any steam coming out.

is there any tests i can do to locate the leak or just any other things i can do.

a pressure check can be done which would show up any external leaks.