Bleeding GM ABS brakes, specifically those found in 1995 to early 2000s GM trucks equipped with the Kelsey-Hayes EBC310 system, can be tricky without a scan tool. This system, with its three distinct sections (left-front, right-front, and rear axle), each containing an isolation valve and a dump-valve/low-pressure accumulator, presents a unique challenge. The low-pressure accumulator is positioned behind the dump valve, making it inaccessible for traditional bleeding methods.
The factory-approved procedure for bleeding these brakes involves using a Tech 1 Scan Tool to initiate ABS cycling. This process flushes fluid and air from the system effectively. However, for those without access to a scan tool, an alternative method exists. This involves driving on a gravel or snow-covered road and forcefully applying the brakes to induce wheel lockup, thereby triggering the ABS cycle.
This “shade-tree” method, while functional, has inherent risks. First, the brakes must be in sufficient working order to safely navigate to a suitable road surface. Secondly, when the ABS cycles, air trapped in the accumulators is released into the brake lines. This can significantly diminish braking performance, potentially creating a hazardous situation. Furthermore, successful activation of all three circuits (left-front, right-front, and one rear wheel) is crucial for proper bleeding.
Assuming successful ABS cycling, the vehicle must be carefully driven back and the remaining air bled from the system using conventional methods. While this approach can be effective, it’s essential to understand the potential dangers and proceed with caution. A thorough understanding of the braking system is paramount before attempting this procedure. Remember, safety should always be the top priority.
For a more detailed explanation of ABS bleeding procedures, consult professional resources like Brake & Front End Magazine’s article “Bleeding ABS Systems” by Bill Williams (July 2005): http://www.babcox.com/editorial/bf/bf70518.htm This resource provides valuable insights into various ABS systems and bleeding techniques. Always prioritize safety and consult professional guidance when working on your vehicle’s braking system.
