Power brake systems using "hydro-boost" may leak power steering fluid from the hydro-boost unit located behind the brake master cylinder. Replacement of the hydro-boost unit is the common repair to correct this concern.Google+
Car Problem Reports
Chevrolet 2500 Pickup Power Brake Units May Leak Fluid From Hydro-Boost Unit
Chevrolet 2500 Pickup Problem
Average Mileage: 122,333 mi (90,000 mi - 157,000 mi)
Visitor, 1999 Chevrolet 2500 Pickup, 120,000 mi
Seal leak on the hydro-boost unit. Leaking powersteering fluid badly
Visitor, 1999 Chevrolet 2500 Pickup, 157,000 mi
leaking power steering fluid at unit and also inside cab onto floor causing slick brake & accelerator pedals and general mess.
Visitor, 1995 Chevrolet 2500 Pickup, 90,000 mi
Leak in the power brake booster for 95 CK2500 suburban. Replaced the booster!