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Question about bleeding brakes, master cylinder and ABS
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Author:  PAGNAM [ Mon Nov 11, 2013 7:37 pm ]
Post subject:  Question about bleeding brakes, master cylinder and ABS

Hey Everyone,

This is my first post, but likely not my last. I just inherited a 2003 Bonneville, but she has a few problems that I need to fix before I can get her on the road.

Today, I tried taking her out for a test drive, and suddenly lost all brake pressure (luckily I was still in the driveway). Some careful shifting between D, N and P got me back into the garage without said brakes. I found the leak, it was coming from the solid brake line going from the ABS module/pump to the front driver side wheel. I replaced the line, and began the procedure for bleeding the brakes. When I got a look at the reservoir, it looked completely empty, I couldn't see any fluid. I topped it up and began bleeding the front driver side caliper. Got some air out, but the pedal still goes right to the floor.

Question 1: I've heard that you can check if your master cylinder is faulty by plugging the outlets and depressing the brakes. If the brakes still go to the floor, then the master cylinder needs to be replaced. What if there is just air in the master cylinder? Could that also cause the problem? Should I bleed the master cylinder before doing that test or would it not make a difference?

Question 2: I've also heard that you need a ScanTool to bleed the ABS system, which I do not have. Is it possible that not being able to bleed the ABS system is causing my problem and even if I were to bleed the master cylinder and all 4 wheels, it would not make a difference without bleeding the ABS system?

Question 3: Everywhere I've looked, the instructions for bleeding brakes say to put pressure on the brake pedal and then loosen the bleeder valve and tighten it back up again while your associate still has their foot on the pedal. If the pedal just goes right to floor anyway, what's the proper procedure?

Thank you for your help! I look forward to becoming an active member of your fabulous community and enjoying my new Bonneville for years to come (very likely with your support).

P.

Author:  xcbullet [ Tue Nov 12, 2013 6:25 pm ]
Post subject:  Re: Question about bleeding brakes, master cylinder and ABS

U need to start by bench bleeding the master cylinder. Unhook the lines let fluid drain out put plugs in & pump master cylinder till no bobbles are seen in the resevor. Then bleed like u mentioned then I like to let gravity bleed after that. Go out if brakes are good on dirt road hit brakes so abs comes on couple times. Go home & re gravity bleed. I go threw about 2-3 quarts to make sure the air is out & fluid is fresh. Sometimes when peddle goes to floor from a leak it can take out the master cylinder.

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