Brakes issue

[Jabu]

Hi

I'm new here, I have an issue with my MK4 golf brakes, it seems there is a leak somewhere, this shows on the front o/s wheel ,it's not the calipers.i have since removed the master cylinder, there was no visible leak.What i noticed is that when topping up the fluid, it immediately goes down to below minimum no idea whhere it drains to. I would appreciate if I can get help please