I am helping a neighbor out in his attempt to bleed his brakes after changing all rotors, front calipers, pads, etc. This started from him repairing the all-wheel-drive and also trying to fix a spongy, to-the-floor brake pedal problem.
He could not get rid of the spongy-to-the-floor problem so he also ended up getting a new aftermarket master cylinder as well. Even in doing so he still has not corrected the core spongy to the floor problem.
He now is also experiencing what appears to be a pressurized break system keeping at least the front discs still staying locked without any pedal pressure. I have a suspicion that this may be due to still having air in the master cylinder tho' he did do a bench bleed on it. What makes me think this is that it took us over an hour to get the brake lines re-attached to the master cylinder thus allowing the reservoir to drain out. Since attaching the lines we've manually bled and re-bled the system at least a dozen times but have yet to correct this or our other issue of spongy-to-the-floor brakes.
We do have a high end scan tool that can do a ABS Brake bleed but really have no idea what the proper and actual GM brake procedure is. We have been trying to activate the ABS Brake bleed sequence for the ABS module and have only had very intermittent success. Sometimes the pedal goes thru a vibration cycle but a lot of times it doesn't.
I'm thinking that for actually doing the ABS brake procedure right you need to be doing a full pressure bleed with one of those brake fluid pressure reservoirs attached to the master cylinder reservoirs and all 4 bleeder screws open, and while this is being done activate the scan tool to do a ABS Brake bleed.
Any thoughts?
Also, I am in disagreement with my neighbor where I believe that if there is air anywhere in the brake system you will not get a fault code, he believes if there is air in the brake system we should be seeing a fault code. who is right?
He could not get rid of the spongy-to-the-floor problem so he also ended up getting a new aftermarket master cylinder as well. Even in doing so he still has not corrected the core spongy to the floor problem.
He now is also experiencing what appears to be a pressurized break system keeping at least the front discs still staying locked without any pedal pressure. I have a suspicion that this may be due to still having air in the master cylinder tho' he did do a bench bleed on it. What makes me think this is that it took us over an hour to get the brake lines re-attached to the master cylinder thus allowing the reservoir to drain out. Since attaching the lines we've manually bled and re-bled the system at least a dozen times but have yet to correct this or our other issue of spongy-to-the-floor brakes.
We do have a high end scan tool that can do a ABS Brake bleed but really have no idea what the proper and actual GM brake procedure is. We have been trying to activate the ABS Brake bleed sequence for the ABS module and have only had very intermittent success. Sometimes the pedal goes thru a vibration cycle but a lot of times it doesn't.
I'm thinking that for actually doing the ABS brake procedure right you need to be doing a full pressure bleed with one of those brake fluid pressure reservoirs attached to the master cylinder reservoirs and all 4 bleeder screws open, and while this is being done activate the scan tool to do a ABS Brake bleed.
Any thoughts?
Also, I am in disagreement with my neighbor where I believe that if there is air anywhere in the brake system you will not get a fault code, he believes if there is air in the brake system we should be seeing a fault code. who is right?