I have lost a lot of brake fluid with no visable leaks.pads f/r good where is it

**My Peugeot 307hdi 52 plate is drinking brake fluid with no visable signs of leaks.I have taken it to the garage but nothing found'Master cylinder and servo are fine ,front and rear pads ok ,no probs with clutch.I have noticed the engine oil is higher than usual,can the fluid get into the engine?????? I need an answer before I dump the car. Cheers Mick