Bulletin Description

THIS BULLETIN CANCELS AND SUPERSEDES DEALER SERVICE BULLETIN NO. 91-74-5 DATED OCTOBER 1990 TO UPDATE THE BLEED PROCEDURE AND TO ADD MODELS SINCE EQUIPPED WITH 4WAL BRAKE SYSTEMS. ALL COPIES OF 91-74-5 SHOULD BE DISCARDED. THIS BULLETIN ALSO UPDATES INFORMATION IN 1993 M/L SERVICE MANUAL, 1993 S/T SERVICE MANUAL, 1993 C/K SERVICE MANUAL, 1993 G SERVICE MANUAL, AND STG RWAL/4WAL 1988-1991 APPLICATIONS MANUAL 15005.05 (VERSIONS 2 TO 5). PLEASE PLACE A COPY OF THIS BULLETIN IN EACH MANUAL. THIS BULLETIN IS EQUIVALENT TO SERVICE MANUAL UPDATE BULLETIN 93-12-5, DATED SEPT. 1992.

This 4WAL brake system bleed procedure is the most efficient bleed procedure to date.

The 4WAL Brake Pressure Modulator Valve (BPMV), formerly called Electro Hydraulic Control Unit (EHCU), should be bled after replacement or if air is suspected to be trapped inside the unit. There are two conventional methods to use when bleeding the 4WAL BPMV: (1.) Pressure Bleeding or (2.) Manual Bleeding.

IMPORTANT:
There are two internal bleed screws (brass colored), one on each side of the BPMV, that open internal channels. Open the internal bleed screws 1/4 to 1/2 turn before bleeding (figure 2). New 4WAL BPMV's are shipped with the internal bleed screws open, so first close the internal bleed screws until snug, then open 1/4 to 1/2 turn.

NOTICE:
Brake fluid will damage electrical connections and painted surfaces. Use shop cloths, suitable containers, and fender covers to prevent brake fluid from contacting these areas. Clean any fluid that may drip onto wheel cylinders or calipers to prevent corrosion. Always re-seal and wipe off brake fluid containers to prevent spills.