Hello 986ohana,
Coolant: first try a new cap. If you still have the problem than water coolant reservoir or the o-ring.
Brakes: when was the system bleeded last time? Should be done every 2 years. If you don't have any maintenance history bleed the brakes and if you have an MT car don't forget to bleed the clutch or let it be done by a workshop.
If you still have problems you should check the brake system.
Neil_B has done some videos of how to bleed brakes and replace brake master cylinder. You should use OEM parts when it comes to brake cylinders.
Parts are available from ATE, Bosch and TRW after market.
Regards, Markus