Power Brake Units May Leak Fluid From Hydro-Boost Unit on GMC Yukon Denali

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.

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Average mileage: 149,250 (94,000–229,000)
8 model years affected: 1999, 2000, 2002, 2003, more2004, 2005, 2006, 2007
15 people reported this problem
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problem details
Power steering pump went out and then hydro boost starting leaking
leak at booster from power steering
2003 GMC Yukon Denali 229,000 mi,
Leaking behind master cylinder
2003 GMC Yukon Denali 150,000 mi,
hydroboost failure was triggering the Service Immediately lights and applying the brakes. replaced hydroboost for around $900 and it fixed it.
2006 GMC Yukon Denali 136,000 mi,
Thought the PS pump was leaking - replaced in my drive. Still had a hard to find leak. Took to good honest shop - diagnosed as the hydrobooster. Waiting on estimate now. See the part is available at O'reilly for about $106 - rebuilt. No sure this is a 'repair in my driveway' type of thing I could do. $584 with labor.
2006 GMC Yukon Denali 178,000 mi,
Once the breech occurred, almost impossible to make right turns and braking is EXTREMELY difficult.