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
GMC 2500 Pickup Power Brake Units May Leak Fluid From Hydro-Boost Unit
GMC 2500 Pickup Problem
Average Mileage: 182,002 mi (86,508 mi - 253,000 mi)
Visitor, 1997 GMC 2500 Pickup, 227,000 mi
POwer Brake Unit LeakS Fluid From Hydro-Boost Unit
Visitor, 1996 GMC 2500 Pickup, 161,500 mi
Bad hydro-boost unit. Had to replace. Advance Auto has rebuilt unit with lifetime warranty for under $200 plus core charge.
Visitor, 2000 GMC 2500 Pickup, 86,508 mi
hydroboost leaking, dealership confirmed must be serviced for $1200!