Found this.....

""""Whenever a caliper or brake line is changed--and we swapped all four calipers and the flexible lines connecting each of the calipers to the "hard" lines on the chassis--the brakes must be bled to remove any air bubbles or pockets form the system, and we learned something quite interesting from the engineers in the R&D department. On late model General Motors anti-lock brake systems, each brake (left-front, right-front, etc.) needs to be bled three times successively, first with the ignition in a key-off position, re-bled with the ignition key in the on position, and a final bleeding in key-off. It has something to do with the ABS circuits, and if the system is not bled in both key-off and key-on, it can retain air in the lines."""""

here.
http://www.vetteweb.com/tech/vet_0310_breaking/

 

This was posted a few weeks back, and someone (I think it was David Farmer) disputed it. Wish we knew for sure; perhaps an "expert" will post for us. :rolleyes:

 

:confused: :lurk:

 

Read that same article in Vette, and couldn't find it documented in my service manual, nor could I verify it with anyone else, so I discounted it.

Notice that the writer did show some surprise (and probably some skepticism) with the shop's assertion, but didn't challenge it directly. Probably the same way we are when we go to a referred shop.

Have a good one,
Mike

 

Guys, I might be getting up to 50 in the amount of brake bleeds that I have done on my car and others. I have never had a problem doing it the so called normal way.

But the GM service manual does call for all 01 and newer vettes to be bleed in this sequence: RR,LF, LR and RF.

Fill the brake master cylinder reservoir 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. 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 11®, 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 FRONT wheel hydraulic circuit bleeder valve.

Install a transparent hose over the end of the bleeder valve, then repeat steps 7-11.

With the left front wheel hydraulic circuit bleeder valve tightened securely - after all air has been purged from the left front 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.

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 11®, 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.

Important
If it is determined that air was induced into the system upstream of the ABS modulator prior to servicing, the ABS Automated Bleed Procedure must be performed.


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 .

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
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 .