Bleeding brakes on certain GM trucks (1995-early 2000s) equipped with the Kelsey-Hayes EBC310 ABS system presents a unique challenge. This system, with its three sections (left-front, right-front, and rear axle), includes Isolation and Dump-Valve/Low-Pressure Accumulator components. The low-pressure accumulator, positioned behind the dump-valve, can’t be bled conventionally. Properly flushing fluid and air from these areas necessitates cycling the ABS.
The factory-approved method involves using a Tech 1 Scan Tool to command the ABS cycling process. However, for those without access to this specialized equipment, a “shade-tree” mechanic method exists. This involves driving on a gravel or snow-covered road and forcefully applying the brakes, causing wheel lockup and, consequently, ABS cycling.
This approach, while functional, carries inherent risks. First, the brakes must be in sufficient working order to safely navigate to and from the chosen road. Second, ABS cycling pushes air from the accumulators back into the brake lines, potentially compromising braking performance significantly.
Assuming successful activation of all three circuits (left-front, right-front, and one rear wheel), the vehicle can be carefully driven home, where traditional bleeding techniques can remove the remaining air from the system. Remember, each section of the EBC310 system must be activated for complete air removal. This means ensuring both front circuits and at least one rear wheel lock up during the ABS cycling process.
This method requires careful execution and awareness of the potential dangers. It is crucial to prioritize safety and ensure the vehicle is operational enough for the procedure. After cycling the ABS, meticulously bleed the brake lines again to ensure all trapped air is eliminated, restoring optimal braking functionality. For a deeper understanding of ABS bleeding procedures, further research is recommended.
For a more in-depth look into bleeding ABS systems, consult resources like the article “Bleeding ABS Systems” by Bill Williams (July 2005) in Brake & Front End Magazine. (http://www.babcox.com/editorial/bf/bf70518.htm)
