BPI 05-07 Brake Hydro-Boost Relief Valve

Bulletin BPI 05-07
Subject:
Brake Hydro-Boost Relief Valve Seal Fracture
Vehicle Involved: General Motors, 2003-2004 model year Cadillac Escalade,
Chevrolet Silverado, Avalanche, Suburban, GMC Sierra, Yukon, Savana, Hummer H2,
and 2004 Chevrolet Tahoe
Condition: During brake application an engine compartment noise similar to the
noise of a steering wheel turned to a full stop position. May also have an increase in
steering and braking effort. If this occurs, it could result in a vehicle crash without prior
warning. 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 a fracture
of the relief valve o-ring seal within the module.
Repair Procedure: Identify that the vehicle pertains to the recall GM TSB #04004A.
With the ignition off pump the brake pedal 10 times to relieve stored hydraulic pressure.
Remove and reposition the master cylinder away from the hydraulic brake booster so
that the machined surface of the booster may be inspected.
Inspect the two o-rings on the original valve for signs of damage; inspect the bore of the
hydraulic brake booster for any pieces or debris using a non-metallic tool or a lint free
towel.
Insert the new relief valve into the bore and tighten to 13ft.lbs. Clean up any fluid that
leaked out of the hydraulic brake booster while removing the original valve.
Position the master cylinder and combination valves on the mounting bolts on the
hydraulic brake booster.
With the master mounted flush to the booster install the nuts to 24 ft. lb. ft.
On vans install the diagonal brace and splash- guard. Install the two bolts and torque to
18ft.lbs.
Start the engine and verify hydraulic brake booster function as good and assisted
feeling. Turn the engine off and check the power steering fluid reservoir. Add fluid if
necessary. Close the hood and test drive.
Affinia Under Vehicle Group 4400 Prime Parkway McHenry, IL 60050 (815) 363-9000
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