I cant get the air to bleed out of my brakes on a 1997 dodge dakota i put on a new master cylender and have been bleeding them for 2 days they seem to bleed normal when truck is not running pump up and fluid drains out but whern i start the truck the pedal goes to the floor easily and i have to pump to get any brake

If the master cylinder is replaced, care must be taken to prime the new master cylinder by removing all of the air and completely filling it with brake fluid. The spongy feeling is air that is still in the circuits. You will need to bleed the back brakes as well as the front ones again. The order that you bled them seems correct, but perhaps there remained some air in the main trunk lines.

For the best results 2 people are needed. Start at the further distance wheel cylinder and bleed at least three (3) master cylinder reservoir volumes of fluid (back brakes). Bleed the fluid with use of a piece of tubing attached to the bleed port that is long enough to reach almost to the bottom of a long neck or tall clear jar (clear drink bottle works well). When the bleeding begins, after one or two brake pedal pushes, make sure that the end of the tubing is below the surface of the fluid and keep it under. It best to have a clear bleed line (to observe air). Keep pumping the brake pedal while being careful to not completely empty the master cylinder reservoir (leave 1/4 full always). Repeat the same technique for each wheel cylinder with at least two (2) reservoirs full for front brakes. Partially close the bleed ports when almost finished (at least 5 pedal strokes without exit of any air). Completely close the ports during the down stroke of the brake pedal, with the tubing still attached. Be sure each bleed port is closed snuggly.
Most of the brake fluid can be reused, but not the darker portion at the bottom of the jar.

when bleeding brakes start at the master cyl lines. crak the nuts at the lines and pump the pedal until you have oil coming out . This primes the master cyl.. Next start at the longest line and bleed back to the shortest. Two man operation . Pump and hold down and then open the bleed screw . tighten the bleed screw and allow the pedal to come back up re-pump the pedal and hold down until all the air is out of that line. Repeat the process fpr all the lines ensuring that you monitor the oil level in the reservoir so that you do not have to start again.

the reason may be : the brake booster is lack of pressure.

It's the master cylinder, Theresa. It will need replacing, because the internal seals are not holding against pressure.
It is not a job for just anybody, but somebody with some experience in bleeding the master cylinder and then bleeding the individual wheel brakes could do it. It's a procedure for getting all air out of the system after replacing parts.

Did you bleed master cylinder before you installed it? If not you will never bleed air out. Bleed kit should have come with it. If you done this need to bleed wheel farthest from master cylinder first and so on.

you will have to bench bleed the new master brake cylinder. you can buy a kit the contains fittings and hoses to do this on the car. When you install a new master brake cylinder without bench bleeding it first air will remain trapped inside and no amount of wheel cylinder bleeding will remove it.

sounds like you still have air in the lines or maybe you have got a master cylinder on the way out.

You 're brake master cylender has failed.
How to change it.

Use a flare wrench and remove the two brake lines.
Then remove the the two nuts that hold it to the fire wall.
Then remove.
Then remove the master cylinder reservoir because your
going to have to put it on the new one.
Drain out any brake fluid from it.
In stall the reservoir on the new master cylinder.
Now you'll have to prime the new master cylinder.
Put the master cylinder in a vise and put brake fluid into it.
Now place your fingers over the two holes that the brake line go into.
Use a large phillips screw driver and push the piston in and out about 10 times.
But, do it slowly. make shore to keep your fingers over the brake line holes. .
Now install it back in.
Remember to bleed your brake system when your done.
Hope this helps give feedback and good luck FixYa

Dakota, 2001-2005

Bleeding the Brake System
Brake fluid tends to darken over time. This does not necessarily indicate contamination. Examine fluid closely for foreign matter.
The primary and secondary hydraulic brake systems are separate and are bled independently. During the bleeding operation, do not allow the reservoir to run dry. Keep the master cylinder reservoir filled with brake fluid. Never use brake fluid that has been drained from the hydraulic system, no matter how clean it seems.

1. Clean all dirt from around the master cylinder fill cap, remove the cap and fill the master cylinder with brake fluid until the level is within 1 / 4 in. (6mm) of the top edge of the reservoir.
2. Clean the bleeder screws at all 4 wheels. The bleeder screws are located on the back of the brake backing plate (drum brakes) and on the top of the brake calipers (disc brakes).
3. Bleeder screws should be protected with rubber caps. If they are missing, the orifice may easily become clogged with road dirt. If the screw refuses to bleed when loosened, remove it and blow clear. Aftermarket caps are readily available.

Bleeding the ABS System
This is accomplished using the same methods as for the base brake system. Refer to those procedures.
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. Refer to the appropriate section.
2. Connect the scan tool to the data link connector beneath the dashboard.
3. Select "Antilock Brakes" followed by "Miscellaneous", then "Bleed Brakes". Follow the instructions displayed until the unit displays "Test Complete", then disconnect the scan tool and proceed.
4. Perform a base brake bleeding a second time.
5. Top up the master cylinder.

Hope helps (remember rated and comment this).

Master cylinter is shot is my first thought. if it has been replaced with a referb.. replace it again. make sure you bench bleed the master cylinder before putting it on.. if it's new, you have a ton of air in the lines.. bleed the pass rear first/ drivers rear/ pass front/ pass rear.. FYI your brakes/ tires should never lock up, you have ABS.