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

Chances are your truck has four-wheel anti-lock brakes. If air was allowed to get into the steel lines, it will have collected inside the ABS hydraulic controller. A scanner is needed to command the computer to open two valves so those chambers can be bled. The entire procedure takes all of about 15 to 30 seconds, and will typically require bleeding the two right wheels. The correct instructions will appear on the scanner's screen and in the guide below.

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

and

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

Please run down this guide and report back.

Check the brake master cylinder could be leaking internally giving you the sink to the floor problem. 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.

Nice work, we are here to help, please use 2CarPros anytime.

Did you bleed the master cyl on the bench and did you do a full brake system bleed? Sounds as if there is air trapped in the system still.

Yep air can get stuck inside the ABS system in which case you will need a shop to use their scanner to open the valve while bleeding the system.

Please let us know what happens

Cheers, Ken

Hi,

If nothing was opened, then you should have a the same brake pedal. I assume the brake fluid isn't low. In a hydraulic system like this, if the pedal goes to the floor and there are no leaks, (and nothing has been opened to allow air into the system) the master cylinder has to be bad. The chances of it happening when you worked on something different are slim, but nothing else makes sense.

Here is a link covering possible causes, but it sounds like you have already checked everything:

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

I am going to provide the directions for bleeding the ABS, but I can't see how that is the problem. Here are the directions which do require a scan tool:

______________________
2007 Dodge or Ram Truck RAM 1500 Truck 2WD V8-5.7L VIN 2
ABS Brake Bleeding
Vehicle Brakes and Traction Control Hydraulic System Brake Bleeding Service and Repair Procedures ABS Brake Bleeding
ABS BRAKE BLEEDING
ABS BRAKE BLEEDING

ABS system bleeding requires conventional bleeding methods plus use of a 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.
2. Connect scan tool to the Data Link Connector.
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.

Let me know.
Joe

Allow me to add a note of great value. Too many people think you have to bleed at the wheels after replacing the master cylinder. That pushes air down the lines, and on about 50 percent of vehicles with ABS, that air gets stuck in two chambers of the hydraulic controller. A scanner is needed to command the ABS Computer to open two valves so that air can be expelled, then you have to complete the procedure by bleeding that air out at two wheels.

Instead, when you replace the master cylinder with two steel lines, loosen the line nuts a little, remove the mounting bolts to the power booster, pull the master cylinder forward, then use it as a handle to bend the steel lines up a little. That will keep the fluid from running out of the lines.

Remove the two lines all the way, then remove the master cylinder. Brake fluid eats paint, so be careful to not allow any to drip onto the car.

Screw the two lines into the new master cylinder that has been bench-bled, then use it to bend those lines back down to their normal shape. Bolt it to the booster, then snug one of the line nuts. Have a helper slowly push the brake pedal half way to the floor. It should take about 15 seconds to do that. You'll see bubbles coming out by that nut. Snug the nut, then holler to the helper to quickly release the pedal.

Do that a second time, and perhaps a third time, until you see only clear fluid with no bubbles coming out, then do that for the other line. By pushing slowly, fluid will get pushed down the lines, and air will float back up. By releasing the pedal quickly, the fluid rushing back will wash the air back up into the reservoir with it. This can even work when working on the car by yourself, just keep the line nuts tight.

Good evening,

By doing the test you did, you have zeroed in on the issue. Make sure the slide pins are free and greased well.

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

You may also have bad calipers even though they are new.

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

Roy

That is not the issue. The calipers themselves could be the issue.

I have to ask this question. Are the bleeders for the calipers at the top of the caliper? If the calipers are on the wrong side, the bleeders will be at the bottom and the air will never come out.

Roy

With the hoses clamped off, and you had a good pedal, the issue is in the front wheels from the hoses to the caliper.

Roy