[mgarblik]

The hole in the back of the MC at the bottom is a weep hole, just like a water pump. When the seal fails it's supposed to drip between the booster and the MC out that hole and not fill up the booster with fluid. I would remove the MC and clean it up good and replace the internal seals with a piston/seal kit. Easy and inexpensive. If there is pitting or deep rust in the bore you need a new MC or that one could be sent out and sleeved with a bronze sleeve if you need to keep it numbers matching. If it has light rust, a quick clean-up with a hone will fix it right up. I would also recommend switching to DOT 4 fluid. It's 100% compatible with DOT 3 but absorbs less water from the atmosphere. Cost just pennies more per pint.