TAC Tech => Mechanical => Topic started by: mereness on January 08, 2022, 07:21:20 PM
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I am restoring a 79 Trans Am with 4 wheel disc brakes. The complete brake system has been replaced, all the way from the rotors, calipers, brake lines, booster, master cylinder, conversion valve, etc. When I try to bleed the brakes the pedal will not get hard and goes to the floor every time. It doesn't seem that the calipers are actuating. The master cylinder was bench primed. The Booster pin (for lack of better terms) was adjusted. Still no actuation in the calipers.
Can someone walk me through the process of bleeding these brakes on a 4 wheel disc system to get the brakes to work? I am starting to think that I ordered the incorrect master cylinder and brake booster.
Thanks in advance for your help!!
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The rear calipers need to be manually adjusted before you will be able to get it to bleed properly. An online search will turn up the tool and procedure.
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An online search will turn up the tool and procedure.
not anymore
lost in the crash
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You don't need a tool to adjust the rear calipers. All you need to do is depress the e-brake pedal a few times. This will adjust the brake pads to the correct position. It's a ratchet type system. As the pads wear down, pressing the e-brake will automatically readjust for the correct position. Now, when it comes time to replace the pads the piston will need to be retracted and a spanner wrench will be needed to "screw" the piston back in. To check if the system is working, engage the e-brake with the car in neutral. Push on the car. If it moves, pump the e-brake a few more times. If it holds , mine you this is not a very good system, the calipers are adjusted. If it still moves after a few attempts then the adjusters are bad.
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https://www.youtube.com/watch?v=opjdu8DdVeA
This video is a great brake down of the rear brakes with the parking brake feature.
I had soft brakes for a few years and 4 mechanic places could not figure it out. I replaced all calipers, pads, master cylinder, and still nothing got better. Sure first drive after the mechanic was fine, but quickly went back to being soft. I saw this great video about and was able to determine the problem. The rear calipers were on the wrong side. What I did to verify was to jack up the car, remove tire. Then looked from the inside, to see which way the parking brake was being pulled, I then applied it with my hands and tried to spin the wheel. Here is my video of me doing it: https://www.youtube.com/watch?v=Y8Xs_fMgN-U
The other side was the same. Once I reversed the calipers so the parking brake was pulling it the right way, which in turn adjusted the calipers, and bled the breaks and BAM!! The brakes were fine and firm. They are not as firm as a new car, so I think I still need to adjust them as well as bleed it one or more times, but this was the solution for me.
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For some reason we have two can't-bleed-my-rear-brakes threads at the same time. I won't merge this (yet), but do go look at the other one.
http://transamcountry.com/community/index.php?topic=84090.0
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Also in November:
http://transamcountry.com/community/index.php?topic=84021.0
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The calipers could be on the wrong side as mentioned above. On the end of the adjuster screw, there will be a "R" or an "L for right and left. Be sure you have one of each on the correct side. A mismatch could also be an issue. i.e Two lefts or two rights.
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https://www.youtube.com/watch?v=SktF3ERaMC8
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https://www.youtube.com/watch?v=SktF3ERaMC8
This is a great video. The one I posted goes further with break down and rebuild, but this gets right to the point. Plus it mentions additional levers that can be purchased, I wonder if there is a standard size, I would love to replace mine just to get it dialed in just a tad bit more.