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I have a 2004 Chevrolet Suburban. I changed the brake calipers because they were leaking. I think the brake system is working in the front but not in the back. Does anybody have a way to troubleshoot or solve this problem?

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    Please clarify the problem: what does The brake system seems to be working in the front but not in the back mean exactly? How are you verifying this? Also, please use proper grammar and syntax when writing your posts here. It helps with readability. – JoErNanO May 18 '16 at 11:46
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If you've changed the calipers and the pedal now goes all the way to the floor, chances are that you've introduced air into the system whilst you had the calipers off.

To fix this, you need to "bleed" the braking system. At each brake caliper / wheel cylinder there is a bleed nipple or bleed screw. The basic procedure is to start at the wheel furthest from the master cylinder, fit a tight fitting capillary tube over the nipple and placing the other end in a container. Loosen the screw and have someone pump the brake pedal until the fluid runs clear with no bubbles. Repeat for each wheel and your pedal should firm up nicely.

Remember to keep topping up the brake fluid reservoir with new fluid as if the level drops too low, you'll have to start all over again.

One final note, when you have the new bottle of brake fluid, DO NOT SHAKE IT. Shaking it can introduce bubbles into the fluid which you don't want.

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    Even more of a warning, DON'T let the level of the brake fluid in the resevoir get low enough to reach the master cylinder. If it gets low enough you will have to bench bleed the master cylinder, and that will add a lot of time (hours) to the job. Keep that fluid topped off and don't let it go low.Remember that you have to fill both front and rear parts of that reservoir. Each one feeds a different cross the front and rear brakes. Missing this again means a master cylinder bench bleed. – cdunn May 18 '16 at 15:24
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I have a 97 suburban. I am not sure how similar things are. I have replaced lines/hoses/calipers/wheel cylinders on this truck and spent hours of time and over a gallon of fluid trying to get it bled correctly. A couple things that I've learned and have helped.

If the master ran dry, be sure to bench bleed the master and ABS. Remove the lines, install short lines, and have them go back to the reservoir on the master. Pump until no bubbles. Reinstall the lines that go from the master to the ABS. Individually bleed the lines that come out of the ABS pump. I didn't try bleeding the ABS, but I think it would had helped as I am almost positive my issues were at the ABS pump.

A couple methods I've used:

Normal pump bleeding - Open the bleeder, push the pedal down, close the bleeder, release the pedal. This will help from air getting trapped. I never quite got it right with this method. I was using the old hose in a bottle method and not closing the bleeders in between pumps.

Pressure bleeding - apply pressure to the master cylinder reservoir to push fluid through. Might had worked had the top been able to seal well, but it ended up just making a big mess.

Vacuum bleeding - apply vacuum at the bleeder. I've used a hand pump and a large vacuum pump. Be sure to use a ton of Teflon tape so you don't suck air from around the threads. If your line doesn't fit tight around the bleeder, you will get tons of bubbles.

Reverse bleeding - Push fluid from the bleeder back through to the master. I build a 'tool' to do this. A sauce jar with one line that I could connect to the air compressor, and one submerged line that would push fluid through. I used a regular to limit the pressure to about 3 PSI. Again, use tons of Teflon tape as to not suck air around the threads.

I ended up modifying some bleeders by cutting the tip off so I could screw it all the way down to ensure no air would get past the threads. Used a ton of Teflon tape. Vacuum bleed until I purged the line, reverse bleed, install original bleeder with a ton of Teflon tape, vacuum bleed until I don't see bubbles. Keep a good eye on the reservoir, you don't not want to run it dry or you will have to start over.

I think the reverse bleeding helps get the bubbles out near the master/abs where there is a long drop. The bubbles want to go up, and normal methods are trying to push them down. I might had had good success with bench bleeding the ABS first also.

You should also note, at least on my truck, part of the process is to have the dealer run an automated bleed on the ABS system. This takes a very specific scan tool. I tried several of my cousin's professional Snap-On scan tools, and they were not able to do the ABS bleed. Since your vehicle is newer, there may be more scan tools that can bleed your ABS pump.

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    Bench bleed an ABS? – Moab May 18 '16 at 14:39
  • Basically try to get all the air out of the ABS pump before trying to bleed the rest of the system. If there are bubbles trapped in the ABS, you will not be able to get it bled correctly. – rpmerf May 18 '16 at 17:28

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