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.
Car Problem Reports
Cadillac Escalade Power Brake Units May Leak Fluid From Hydro-Boost Unit
Cadillac Escalade Problem
Visitor, 2005 Cadillac Escalade, 138,000 mi
Start small leak , and gets worse I fix it by changing the hydro boost , I spend around $ 280 on part and about, 2 hours of work