Master Cylinder Bench Bleeding Non-Hybrid

Warning: Refer to Brake Fluid Irritant Warning in the Preface section.

Caution: Refer to Brake Fluid Effects on Paint and Electrical Components Caution in the Preface section.

1. Secure the mounting flange of the brake master cylinder in a bench vise so that the rear of the primary piston is accessible.
2. Remove the master cylinder reservoir cap and diaphragm.
3. Install suitable fittings to the master cylinder ports that match the type of flare seat required and also provide for hose attachment.
4. Install transparent hoses to the fittings installed to the master cylinder ports, then route the hoses into the master cylinder reservoir.
5. Fill the master cylinder reservoir to at least the half-way point with GM approved brake fluid from a clean, sealed brake fluid container. Refer to Master Cylinder Reservoir Filling.
6. Ensure that the ends of the transparent hoses running into the master cylinder reservoir are fully submerged in the brake fluid.
7. Using a smooth, round-ended tool, depress and release the primary piston as far as it will travel, a depth of about 25 mm (1 in), several times. Observe the flow of fluid coming from the ports.

As air is bled from the primary and secondary pistons, the effort required to depress the primary piston will increase and the amount of travel will decrease.

8. Continue to depress and release the primary piston until fluid flows freely from the ports with no evidence of air bubbles.
9. Remove the transparent hoses from the master cylinder reservoir.
10. Install the master cylinder reservoir cap and diaphragm.
11. Remove the fittings with the transparent hoses from the master cylinder ports. Wrap the master cylinder with a clean shop cloth to prevent brake fluid spills.
12. Remove the master cylinder from the vise.

Master Cylinder Bench Bleeding Two-mode Hybrid

Warning: Refer to Brake Fluid Irritant Warning in the Preface section.

Caution: Refer to Brake Fluid Effects on Paint and Electrical Components Caution in the Preface section.

Note: The ignition must be in the OFF position, without pausing at ACCESSORY, and without applying the brake pedal to ensure the brake modulator and high pressure accumulator (HPA) pressure relief occurs. This process will take approximately 1 to 3 minutes.

1. Turn the ignition to OFF, without pausing at ACCESSORY, and remove the ignition key.
2. Wait approximately 1 to 3 minutes until the brake modulator and HPA pressure relief is complete.
3. Remove the master cylinder reservoir cap and diaphragm.
4. Mark the location of the master cylinder brake pipe fittings (1).
5. Disconnect the master cylinder brake pipe fittings.
6. Install suitable fittings to the master cylinder ports that match the type of flare seat required and also provide for hose attachment.
7. Install transparent hoses to the fittings installed to the master cylinder ports, then route the hoses into the master cylinder reservoir.
8. Fill the master cylinder reservoir to at least the half-way point with Delco Supreme 11®, GM P/N 12377967 (Canadian P/N 992667), or equivalent DOT-3 brake fluid from a clean, sealed brake fluid container.
9. Ensure that the ends of the transparent hoses running into the master cylinder reservoir are fully submerged in the brake fluid.
10. Press and release the brake pedal as far as it will travel several times. With the aid of an assistant, observe the flow of fluid coming from the ports.

As air is bled from the primary and secondary pistons, the effort required to depress the primary piston will increase and the amount of travel will decrease.

11. Continue to press and release the brake pedal until fluid flows freely from the ports with no evidence of air bubbles.
12. Remove the transparent hoses from the master cylinder reservoir.

Caution: Refer to Fastener Caution in the Preface section.

13. Install the master cylinder brake pipe fittings, noting their location and tighten the fittings to  30 N·m (22 lb ft).
14. Fill the brake master cylinder reservoir. Refer to Master Cylinder Reservoir Filling.
15. Install the master cylinder reservoir cap and diaphragm.