93 4wd mushy brake pedal, help please
 

I have a 93 4wd. Over the last year the brake pedal feel has been getting progressively soft. No evidence of leaks around the wheels; however, this week I noticed residue around the fittings on the master cylinder. Does anyone know if this is indication that I have some sort of bypass or is the m/c going bad or a problem somewhere else. I have bled the brakes myself once and had 2 different shops also bleed the brakes. Any help would be appreciated.