Brake Pressure Bleeding and GM Factory Manual

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I have the GM Service Manual for my truck (2006 Sierra) and, in the section on bleeding brakes, it has instructions on how to bleed the brakes manually(two people/pumping pedal), but does not list pressure bleeding as another way to bleed the brakes. The only reference to pressure bleeding is at the end of the manual bleeding section where it asks you to pressure bleed the system if you get a spongy pedal after repeated manual bleeding.

Since the service manual is written primarily for the professional automotive technician most of whom would have access to a pressure brake bleeder, I find it very surprising that there it does not list pressure bleeding as one way to bleed the brakes.

Does anyone know why GM skates around pressure bleeding, at least for the Sierra?
 
I don't know why they only list how to bleed the brakes old school. I've never had a issue with GM's and manual bleeding. But like you say they list pressure bleeding at the end of the article. I will say doing the ABS automatic bleed makes a big difference in pedal feel.

Hydraulic Brake System Bleeding (Manual)

Caution: Refer to Brake Fluid Irritant Caution in Service Precautions.

Notice: Refer to Brake Fluid Effects on Paint and Electrical Components Notice in Service Precautions.

Notice: When adding fluid to the brake master cylinder reservoir, use only Delco Supreme II®, GM P/N 12377967 (Canadian P/N 992667), or equivalent DOT-3 brake fluid from a clean, sealed brake fluid container. The use of any type of fluid other than the recommended type of brake fluid, may cause contamination which could result in damage to the internal rubber seals and/or rubber linings of hydraulic brake system components.

Place a clean shop cloth beneath the brake master cylinder to prevent brake fluid spills.
With the ignition OFF and the brakes cool, apply the brakes 3-5 times, or until the brake pedal effort increases significantly, in order to deplete the brake booster power reserve.
If you have performed a brake master cylinder bench bleeding on this vehicle, or if you disconnected the brake pipes from the master cylinder, you must perform the following steps:

Ensure that the brake master cylinder reservoir is full to the maximum-fill level. If necessary add Delco Supreme II®, GM P/N 12377967 (Canadian P/N 992667), or equivalent DOT-3 brake fluid from a clean, sealed brake fluid container. If removal of the reservoir cap and diaphragm is necessary, clean the outside of the reservoir on and around the cap prior to removal.
With the rear brake pipe installed securely to the master cylinder, loosen and separate the front brake pipe from the front port of the brake master cylinder.
Allow a small amount of brake fluid to gravity bleed from the open port of the master cylinder.
Reconnect the brake pipe to the master cylinder port and tighten securely.
Have an assistant slowly depress the brake pedal fully and maintain steady pressure on the pedal.
Loosen the same brake pipe to purge air from the open port of the master cylinder.
Tighten the brake pipe, then have the assistant slowly release the brake pedal.
Wait 15 seconds, then repeat steps 3.3-3.7 until all air is purged from the same port of the master cylinder.
With the front brake pipe installed securely to the master cylinder -after all air has been purged from the front port of the master cylinder -loosen and separate the rear brake pipe from the master cylinder, then repeat steps 3.3-3.8.
After completing the final master cylinder port bleeding procedure, ensure that both of the brake pipe-to-master cylinder fittings are properly tightened.

Fill the brake master cylinder reservoir with Delco Supreme II®, GM P/N 12377967 (Canadian P/N 992667), or equivalent DOT-3 brake fluid from a clean, sealed brake fluid container. Ensure that the brake master cylinder reservoir remains at least half-full during this bleeding procedure. Add fluid as needed to maintain the proper level. Clean the outside of the reservoir on and around the reservoir cap prior to removing the cap and diaphragm.
Install a proper box-end wrench onto the RIGHT REAR wheel hydraulic circuit bleeder valve.
Install a transparent hose over the end of the bleeder valve.
Submerge the open end of the transparent hose into a transparent container partially filled with Delco Supreme II®, GM P/N 12377967 (Canadian P/N 992667), or equivalent DOT-3 brake fluid from a clean, sealed brake fluid container.
Have an assistant slowly depress the brake pedal fully and maintain steady pressure on the pedal.
Loosen the bleeder valve to purge air from the wheel hydraulic circuit.
Tighten the bleeder valve, then have the assistant slowly release the brake pedal.
Wait 15 seconds, then repeat steps 8-10 until all air is purged from the same wheel hydraulic circuit.
With the right rear wheel hydraulic circuit bleeder valve tightened securely -after all air has been purged from the right rear hydraulic circuit -install a proper box-end wrench onto the LEFT REAR wheel hydraulic circuit bleeder valve.
Install a transparent hose over the end of the bleeder valve, then repeat steps 7-11.
With the left rear wheel hydraulic circuit bleeder valve tightened securely -after all air has been purged from the left rear hydraulic circuit -install a proper box-end wrench onto the RIGHT FRONT wheel hydraulic circuit bleeder valve.
Install a transparent hose over the end of the bleeder valve, then repeat steps 7-11.
With the right front wheel hydraulic circuit bleeder valve tightened securely -after all air has been purged from the right front hydraulic circuit -install a proper box-end wrench onto the LEFT FRONT wheel hydraulic circuit bleeder valve.
Install a transparent hose over the end of the bleeder valve, then repeat steps 7-11.
After completing the final wheel hydraulic circuit bleeding procedure, ensure that each of the 4 wheel hydraulic circuit bleeder valves are properly tightened.
Fill the brake master cylinder reservoir to the maximum-fill level with Delco Supreme II®, GM P/N 12377967 (Canadian P/N 992667), or equivalent DOT-3 brake fluid from a clean, sealed brake fluid container.
Slowly depress and release the brake pedal. Observe the feel of the brake pedal.
If the brake pedal feels spongy, repeat the bleeding procedure again. If the brake pedal still feels spongy after repeating the bleeding procedure, perform the following steps:

Inspect the brake system for external leaks. Refer to Brake System External Leak Inspection . See: Hydraulic System\Testing and Inspection\Component Tests and General Diagnostics
Pressure bleed the hydraulic brake system in order to purge any air that may still be trapped in the system.

Turn the ignition key ON, with the engine OFF. Check to see if the brake system warning lamp remains illuminated.
Important: If the brake system warning lamp remains illuminated, DO NOT allow the vehicle to be driven until it is diagnosed and repaired.

If the brake system warning lamp remains illuminated, refer to Symptoms - Hydraulic Brakes. See: Hydraulic System\Testing and Inspection\Symptom Related Diagnostic Procedures


ABS Automated Bleed Procedure

Notice: When adding fluid to the brake master cylinder reservoir, use only Delco Supreme II®, GM P/N 12377967 (Canadian P/N 992667), or equivalent DOT-3 brake fluid from a clean, sealed brake fluid container. The use of any type of fluid other than the recommended type of brake fluid, may cause contamination which could result in damage to the internal rubber seals and/or rubber linings of hydraulic brake system components.

Notice: Refer to Brake Fluid Effects on Paint and Electrical Components Notice in Service Precautions.

Important: This procedure may be performed on all vehicles EXCEPT those equipped with option code JL4, Vehicle Stability Enhancement System (VSES).

Important: The base hydraulic brake system must be bled before performing this automated bleeding procedure. If you have not yet performed the base hydraulic brake system bleeding procedure, refer to Hydraulic Brake System Bleeding (Manual).

Install a scan tool to the vehicle.
Start the engine and allow the engine to idle.
Depress the brake pedal firmly and maintain steady pressure on the pedal.
Using the scan tool, begin the automated bleed procedure.
Follow the instructions on the scan tool to complete the automated bleed procedure. Release the brake pedal between each test sequence.
Turn the ignition OFF.
Remove the scan tool from the vehicle.
Fill the brake master cylinder reservoir to the maximum-fill level with Delco Supreme II® GM P/N 12377967 (Canadian P/N 992667) or equivalent DOT-3 brake fluid from a clean, sealed brake fluid container.
Bleed the hydraulic brake system. Refer to Hydraulic Brake System Bleeding (Manual).
With the ignition OFF, apply the brakes 3-5 times, or until the brake pedal becomes firm, in order to deplete the brake booster power reserve.
Slowly depress and release the brake pedal. Observe the feel of the brake pedal.
If the brake pedal feels spongy, repeat the automated bleeding procedure. If the brake pedal still feels spongy after repeating the automated bleeding procedure inspect the brake system for external leaks. Refer to Brake System External Leak Inspection. See: Hydraulic System\Testing and Inspection\Component Tests and General Diagnostics
Turn the ignition key ON, with the engine OFF; check to see if the brake system warning lamp remains illuminated.
If the brake system warning lamp remains illuminated, DO NOT allow the vehicle to be driven until it is diagnosed and repaired. Refer to Symptoms - Hydraulic Brakes. See: Hydraulic System\Testing and Inspection\Symptom Related Diagnostic Procedures
Drive the vehicle to exceed 13 kph (8 mph) to allow ABS initialization to occur. Observe brake pedal feel.
If the brake pedal feels spongy, repeat the automated bleeding procedure until a firm brake pedal is obtained.
 
The ABS bleed will only improve pedal feel if air was introduced into the system. In my case I was just flushing out my five year old brake fluid(I know, I should have done it earlier).
 
My GM FSM lists the same thing basically but i always pressure bleed mine using my Motive pressure bleeder.

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Originally Posted By: George7941
The ABS bleed will only improve pedal feel if air was introduced into the system. In my case I was just flushing out my five year old brake fluid(I know, I should have done it earlier).


George I do this on every gm I get in for brake service and I'm not working at a dealership. I feel it has to do more with the dirty fluid around the ABS valves than air. My personal experience is that its starts to become noticeable to the trained eye around 10k of driving.

OMG 5 years on your original brake fluid!!!! That should be worth a few weeks in Timeout!!! LOL
 
Originally Posted By: Ojustracing
Originally Posted By: George7941
The ABS bleed will only improve pedal feel if air was introduced into the system. In my case I was just flushing out my five year old brake fluid(I know, I should have done it earlier).


George I do this on every gm I get in for brake service and I'm not working at a dealership. I feel it has to do more with the dirty fluid around the ABS valves than air. My personal experience is that its starts to become noticeable to the trained eye around 10k of driving.

OMG 5 years on your original brake fluid!!!! That should be worth a few weeks in Timeout!!! LOL



I also do the ABS procedure (I am lucky to own a Tech2, lol) with every brake fluid flush. It helps to move the brake fluid out of the valves.

As far as pressure bleeding, it is listed in the online GM service manuals. No dealers use the paper books anymore.
 
I wished they would put brake bleeders on the ABS unit and allow it to be manually bled, but the bleeders are disappearing from ABS units.
 
Also consider vacuum bleeding - A Mityvac or similar.
It is quick and easy.
Make sure you keep your reservoir filled! Otherwise you have to start all over.
 
Originally Posted By: mechanicx
I wished they would put brake bleeders on the ABS unit and allow it to be manually bled, but the bleeders are disappearing from ABS units.


I agree. My 94 Corvette has a bleeder on the ABS unit, but none of my newer vehicles do. Cost cutting I am sure.
 
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