Bleed ABS brakes

How to bleed ABS brakes

If you’re doing a brake job on a vehicle with ABS brakes and you don’t know how to bleed them, you may get into trouble. Here’s what you need to know about how to bleed ABS brakes.

Start with the recommended brake bleed sequence

In most cases the recommended procedure is RR, LR, RF, and LF brakes. The procedure is designed to start the bleed with the wheel farthest from the master cylinder and then move to the next farthest, etc.

This works as long as you haven’t let the master cylinder run dry during your brake work. However, if the master cylinder did run dry, you’ll have to bench bleed the master cylinder and then bleed the ABS valves.

Air bubbles tend to stay in the ABS valves

ABS systems are VERY sensitive to air bubbles. You know that air rises in the system. Once a bubble gets into the ABS valves, it’s almost impossible to suck it back down even with a hand-held vacuum pump.

Homemade trick to purge air from ABS hydraulic unit

Drive your vehicle to a flat sandy area. Accelerate to about 20-MPH and slam on the brakes until the ABS operates. Repeat several times. Activating the brakes in on sand or gravel can help bleed ABS module. If the brake pedal feels firm after this procedure, you’re done. However, if this doesn’t work, you’ll have to perform a reverse bleed shown below

Two methods to bleed the ABS

1) Force brake fluid backwards from the caliper up through the ABS valves and into the master cylinder using a hand held reverse flush tool. Reverse flush pressure will push the air bubbles up into the master cylinder and out of the ABS valves.

Phoenix 2002HD-B brake bleeder tool

2) Use a scan tool to force an ABS bleed purge procedure

Prevent air from getting into the ABS

How can you avoid getting air into the ABS system? NEVER, and I mean NEVER let the reservoir run dry as you bleed the brakes. ALWAYS, and I mean ALWAYS use a vacuum bleeder. The days of pumping with the brake pedal are OVER. Don’t believe me? Try it yourself. You may skate by.

But if you get air into the system and have to take it to a shop, be prepared to fork over at least $100 for a scan tool bleed procedure. (By the way, you could have bought the vacuum tool for a tad less than that).

© 2012 Rick Muscoplat

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