if its leaking from the small block below the master cylinder, that is called the brake control valve or combination valve. It houses the proportioning valve and the shuttle valve. The proportioning valve is in the front part of the combination valve. Mine was leaking out the the little rubber plug on the front of the combination valve. I unscrewed the cap at the end and replaced the o-rings and that solved my problem. Its much cheaper than buying a replacement, and much easier to fix your problem. Took me 5 minuted and bleed the rear brakes. Where exactly is yours leaking? Where one of the brake lines comes in or from the front or back caps to the combination valve? Ask Matt90gt (i think). hes the expert. hope this helps