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I have a '07 Silverado. Both rear wheel brake cylinders blew apart. I fitted new ones along with new shoes. I have bled the brakes but my pedal still goes to floor. What else can I do?

  • chris - I had to edit to make the question readable. Can you please confirm I haven't changed the meaning. – Rory Alsop Mar 14 '16 at 17:23
  • That looks good – chris Mar 14 '16 at 17:29
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    Have you bled the master cylinder, brakes, and ABS unit? If you lost all the fluid in the master cylinder you'll have to bleed everything. – JPhi1618 Mar 14 '16 at 17:50
  • Agree completely here with @JPhi1618 – Pᴀᴜʟsᴛᴇʀ2 Mar 14 '16 at 18:01
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It's fairly common on GMs when all fluid leaks from the system that you have to bleed the ABS Bypass Modulator Valve. This requires a scan tool with bi-directional controls.

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As JPHi1618 said, you'll have to bleed everything, from the master cylinder on down. And the master cylinder may require "bench bleeding". Google it to find out.

  • I suggest if you could add the bench bleeding steps to your answer of include a specific link. It would be even more helpful if you can tell us in what situations a "bench bleed" is required. – rana Mar 14 '16 at 19:52
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I have a 97 suburban. I've replace just about every piece of hydraulic equipment on the vehicle aside from the hoses on the rear axle and the ABS pump. Since replacing a broken line 2 years ago, the pedal hasn't been the same. I probably put about a gallon of brake fluid through the braking system trying to bleed it correctly. I finally was able to get it bleed completely and I can now lock the wheels on dry pavement. Here is what finally worked for me.

Pull the bleeders off, clean them, install Teflon tape so they make a good seal. Bleed the vehicle with the normal 2 person method, vacuum bleeding, or pressure bleeding. If doing the 2 person method, close the bleeders before releasing the pedal. This will get out any bubbles near the calipers/wheel cylinders.

There is a catch, any bubbles near the master cylinder or ABS will want to go up, and there is a good 1 foot drop to the bleeders. I did a reverse bleed. This pushes fluid from the bleeders to the master cylinder. You want to make sure you have a good bleed on the system first, so you are not pushing dirty fluid back through the system. After doing a reverse bleed, do a normal bleed again to ensure there are not bubbles trapped around the caliper/wheel cylinder.

Here is a company that makes a reverse bleeder. http://www.brakebleeder.com/

I was able to build my own with a glass jar, some clear hose, and a connection to the air compressor with a regulator. I took an extra set of bleeders and cut the tip off, so I could screw it in all the way to avoid leaking around the threads. It seemed to work well, but I got brake fluid everywhere.

  • I would disagree with putting teflon on the bleeders, they do not seal on the threads, they should seal against the seat in the bottom of the hole. – john D. Jun 22 '16 at 1:51
  • The Teflon is for when the bleeders are open to let fluid through to ensure air isn't sucked in around the threads. Correct, when they are closed they should seal against the bottom. – rpmerf Jun 29 '16 at 16:31

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