Hmmmm....
Part 1:
Document ID# 1528250
F/CMVSS Noncompliance - Brake Hydro-Boost Relief Valve Seal Fracture #04004A - (Jun 18, 2004)
2003-2004 Cadillac Escalade, Escalade EXT, Escalade ESV
2003-2004 Chevrolet Silverado, Avalanche, Suburban, Express
2004 Chevrolet Tahoe
2003-2004 GMC Sierra, Yukon, Yukon XL, Savana
2003-2004 HUMMER H2
THIS BULLETIN CANCELS AND REPLACES BULLETIN 04004, ISSUED JUNE 2004. THE INSPECTION PROCEDURE IN THIS BULLETIN HAS BEEN REVISED TO INCLUDE ADDITIONAL STAMPED NUMBERS ON THE HYDRAULIC BRAKE BOOSTER. ALL COPIES OF BULLETIN 04004 SHOULD BE DESTROYED.
Condition
General Motors has decided that certain 2003 and 2004 model year Cadillac Escalade, Escalade EXT and Escalade ESV; Chevrolet Silverado, Avalanche, Suburban, and Express; GMC Sierra, Yukon, Yukon XL, and Savana; HUMMER H2; and 2004 model year Chevrolet Tahoe vehicles fail to conform to either Federal/Canada Motor Vehicle Safety Standard 105, "Hydraulic and Electric Brake System", or Standard 135, "Light Vehicle Brake Systems". These vehicles may have a relief valve bore within the brake hydro-boost module that is not to specification. An out-of-specification bore could result in fracture of the relief valve o-ring seal within the module. If this happens, during brake applications the driver may be able to hear an engine compartment noise similar to the sound that occurs when the steering wheel is turned to a full stop position. The driver could also experience a slight increase in steering efforts while braking and parking. Under certain driving conditions, a fractured seal may require a slight increase in the applied brake pedal effort to achieve the same vehicle deceleration rate as prior to the seal fracture. If this were to occur, it could result in a vehicle crash without prior warning.
Correction
Dealers are to inspect the hydro-boost module and replace the relief valve, if necessary.
Vehicles Involved
Involved are certain 2003 and 2004 model year Cadillac Escalade, Escalade EXT and Escalade ESV; Chevrolet Silverado, Avalanche, Suburban, and Express; GMC Sierra, Yukon, Yukon XL, and Savana; HUMMER H2 and 2004 model year Chevrolet Tahoe vehicles built within these VIN breakpoints: