Also, to add to the advise of the others, make sure your brakes are adjusted properly. The fluid coming back to the master is coming from the wheel cylinders. When the shoes have to expand a long ways, it takes more fluid going out . Then when you release your pedal, the fluid comes back. It usually comes back fast enough to bubble over the master a makes a heck of a mess. Brake fluid strips paint too.
Just a thought,
Scott
