Changed the brakes and the Master cylinder the pedal still goes to the floor

BLEEDING PROCEDURES Complete Brake System Before bleeding system, exhaust all vacuum from power unit by depressing brake pedal several times. Bleed master cylinder using bleeder screws (if equipped). These videos and guides can help us fix it.

https://youtu.be/w7gUsj2us0U

and

https://youtu.be/WDxvEQrMkBg

and

https://www.2carpros.com/articles/brake-pedal-goes-to-the-floor

Please run down these guides and report back.

Bleed wheel cylinders and calipers in sequence. See BLEEDING SEQUENCE table.

Master Cylinder (Bench Bleeding) 1. Bench bleed master cylinder before installation. Place master cylinder in soft-jaw vise. Install bleeder tubes in both outlets of master cylinder. See Fig. 1 . 2. Fill master cylinder with clean brake fluid. Ensure ends of bleeder tubes are submerged in brake fluid. 3. Using a wood dowel, apply and release master cylinder until no air bubbles exist in brake fluid flow. Leave bleeder tubes installed on master cylinder during installation. Install master cylinder. Remove bleeder tubes, and connect brakelines. Bleed brake system if necessary.

Vacuum Bleeding Fill master cylinder. Install vacuum bleed equipment to first bleeder valve to be serviced. Open bleeder valve 3/4-1 turn. Depress vacuum pump, and pull fluid into reservoir jar. Bleed each bleeder valve in sequence. See BLEEDING SEQUENCE table. Pressure Bleeding 1. Clean master cylinder cap and surrounding area. Remove cap. With pressure tank at least 1/2 full, connect it to master cylinder using appropriate adapters. Attach bleeder hose to first bleeder valve to be serviced. See BLEEDING SEQUENCE table. 2. Submerge other end of hose in clean glass jar partially filled with clean brake fluid. Position metering valve properly before pressure bleeding. 3. Open release valve on pressure bleeder. Follow equipment manufacturer's pressure bleeding
CAUTION: When using pressure bleeding method, press and hold in valve stem on combination valve to properly bleed brake system.

If this is not the sequence you followed, you may have to bleed it once more in this sequence. Master cylinder, combination valve, rear anti-lock valve, right rear, left rear, right front and left front. Before bleeding system, exhaust all vacuum from power unit by depressing brake pedal several times. If after that you still have the problem or just want to check the vacuum boost. These guides can help fix it.

https://www.2carpros.com/articles/brake-pedal-goes-to-the-floor

and

https://www.2carpros.com/articles/how-to-bleed-or-flush-a-car-brake-system

Please run down these guides and report back.

Good afternoon.

I attached the procedure for bleeding with ABS. You need a scan tool to bleed the ABS unit.

It sounds like you still have air in the system.

Roy

ABS system bleeding requires conventional bleeding methods plus use of the DRB scan tool. The procedure involves performing a base brake bleeding, followed by use of the scan tool to cycle and bleed the HCU pump and solenoids. A second base brake bleeding procedure is then required to remove any air remaining in the system.

1. Perform base brake bleeding.
3. Select ANTILOCK BRAKES, followed by MISCELLANEOUS, then ABS BRAKES. Follow the instructions displayed. When scan tool displays TEST COMPLETE, disconnect scan tool and proceed.
4. Perform base brake bleeding a second time.
5. Top off master cylinder fluid level and verify proper brake operation before moving vehicle.

If the bleeder screw is on the bottom, you have the caliper on the wrong side. There's no way air is going to go down and brake fluid go up to get the air out.

I'm the master at getting the last ounce of life out of anything, but I draw the line at used brake parts. There's way too many variables that will result in unbalanced braking power side-to-side. Back in the '80s when we commonly rebuilt calipers and wheel cylinders as a part of a standard brake job, a replacement caliper piston could cost $20.00, the rebuild kit another $10.00, then you still had an hour of work to do the job. Today professionally-rebuilt calipers are extremely inexpensive, so there's no value in using used parts.

Depending on the model of the truck, and the year, there were also calipers with 80mm pistons and with 88mm pistons. Both sizes were available as standard or a low-drag version. That means there's four different calipers that can be bolted onto one corner of your truck. There's a 32-page service bulletin to address a very sudden, and very hard brake pull to one side that shows up unexpectedly after a number of hard stops in a row. One of the things we had to check was that the calipers were matching.

If you're determined to use the wrong caliper, there's two ways to get the air out. One is to unbolt it, hold it with the bleeder screw up, then let it gravity-bleed until the air bubbles stop showing up. Another way is to leave it bolted in place, then loosen the banjo bolt that holds the flexible rubber hose onto it. Tighten the bolt when air bubbles stop coming out.

Given the age of the truck, (more than a year old), if you've been running the brake pedal all the way to the floor, it is likely the master cylinder has also been damaged. Crud and corrosion build up in the lower halves of the bores where the pistons don't normally travel. Pushing the brake pedal to the floor runs the rubber lip seals over that crud and can rip them. That results in a slowly-sinking brake pedal, and that often takes two or three days to show up. This is another place where salvage yard parts are a very poor value. Any replacement master cylinder will have to be bench-bled before it is installed, and that can result in the same problem.

As a brake system specialist, I have only used gravity-bleeding since the late '80s. For those who use pedal-bleeding, the helper must be instructed to never push the brake pedal over half way to the floor.

You can find more information in these articles:

https://www.2carpros.com/articles/brake-pedal-goes-to-the-floor

https://www.2carpros.com/articles/brake-caliper-replacement

https://www.2carpros.com/articles/how-to-replace-a-brake-master-cylinder

Here's links to some related videos too. This first one is on bleeding brakes:

https://youtu.be/w7gUsj2us0U

This second one shows how to bench-bleed a master cylinder:

https://youtu.be/WdxvEQrMkBg

Please keep me updated on your progress.

Hello,

Sounds like your master has failed, which is possible, I've seen it before after doing a brake job. Two main things trigger the main brake light to go besides the ABS system, your low on fluid or there's an imbalance between the left and right hydraulic fluid circuits caused by a leak or air in one side but just to verify before going through the steps to change the Master cylinder out. First get in the car turn it on and pump the pedal, after a few times pumping it up the pedal should ride high at this point give it one good hard press. You may hear a click sound, this is the gate in the system that senses if there is an imbalance resetting itself. Stop pumping and just wait a minute then press the pedal if it goes to the floor your master is bad and we can send you all the information you will need to change it out. Did the system completely drain its fluid out, do you think you got air into the ABS block?
Let us know what happens.

TomI have added few videos for you to watch that will help and should shed some light into your issue.

https://youtu.be/Pb6nXV-iamI

https://youtu.be/rTtAnsOlZU4

https://youtu.be/ANWVTh2RQoQ

Check them out and let us know how you do.