How to Bleed an Accumulator-Type ABS Brake System

Toyota Prado 120 Series
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Introduction

This article describes a method for bleeding an accumulator-type ABS brake system, focusing on troubleshooting spongy brake feel after brake caliper replacement or fluid changes. It addresses issues encountered when air becomes trapped in the ABS/ESP system.

Problem

A spongy brake pedal feel after replacing front brake calipers, potentially caused by air trapped within the ABS/ESP accumulator system. Traditional bleeding methods may prove ineffective. The system may exhibit the following symptoms:

  • Spongy pedal with engine on.
  • Pump sounds like it’s pumping air, especially when the ignition is switched on.
  • Possible ABS/VSC warning lights and continuous pump operation if the system is severely compromised.

Solution

The following bleeding procedure, adapted from a recommendation, may resolve the issue:

  1. Initial Bleeding: Begin by bleeding all four brake calipers. It is crucial to address all wheels, starting with the rears, even if the initial work was only on the front.
  2. Manual Bleeding Process (Two People Required):
    • Turn the ignition to the “ON” position (engine off).
    • Pump the brake pedal 20 times.
    • Bleed the rear calipers first, starting with the left rear, then the right rear, while holding the pedal down.
    • Top up the brake fluid reservoir to the maximum level. Aim to remove approximately 250ml of fluid from each side during this step, checking the reservoir level between sides.
    • Bleed the front calipers (left, then right) using a stroke bleeding method. Remove approximately 250ml from each side, and check the reservoir level in between each side.
    • Top up the reservoir to the maximum line again.
    • Return to the rear calipers and repeat the bleeding procedure, this time removing about 150ml from each side.
    • Top up the reservoir to just below the maximum line.

Notes

  • This process removes approximately 1 to 1.3 liters of brake fluid, effectively replacing most of the moisture-saturated fluid.
  • Ensure the brake fluid reservoir is consistently topped up during the bleeding process to prevent more air entering the system.
  • If the accumulator has air in it, you may require a specialist workshop to complete the bleed.

This technical summary was auto-generated based on recovered archives. Do not rely on its factual accuracy. Refer to the original thread. Source: View Original Conversation

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