Bleeding brakes on certain GM trucks (1995-early 2000s) with the Kelsey-Hayes EBC310 ABS system requires cycling the ABS valves to fully flush the system. This system has three sections: left-front, right-front, and rear axle, each with an isolation valve and a dump-valve/low-pressure accumulator. The accumulator, positioned behind the dump valve, prevents traditional bleeding methods from accessing trapped air.
The factory recommended procedure involves using a Tech 1 Scan Tool to command the ABS cycling. This tool directly interacts with the ABS computer, initiating the valve cycles needed to release trapped air and fluid from the low-pressure accumulators.
However, a common workaround, often employed by DIY mechanics, involves driving on a gravel or snow-covered road and forcefully applying the brakes to induce wheel lockup and trigger the ABS. This method forces the ABS to cycle, effectively pushing fluid and air out of the accumulators.
This alternative method presents some inherent risks. First, the brakes must be functional enough for safe driving to reach a suitable surface for inducing ABS activation. Secondly, cycling the ABS in this manner can introduce air from the accumulators back into the brake lines, potentially compromising braking performance. Ideally, all three circuits (left-front, right-front, and one rear wheel) should activate for a complete flush. After cycling the ABS, carefully return and bleed the remaining air from the system using conventional methods.
Despite the workarounds, accessing and cycling the ABS valves without a scan tool on these specific GM truck models poses challenges. The official method using the Tech 1 scan tool remains the safest and most reliable procedure to ensure complete air removal and optimal braking system performance.
For further information on bleeding ABS brake systems, consult professional automotive resources like “Bleeding ABS Systems” by Bill Williams (July 2005) in Brake & Front End Magazine.
