2000 Dodge Ram pickup Brake Help?

that almost sounds like a master cyl. leak. however, yes the ABS controller can do that as well. one thing you could do is break free the line on the master that goes to the rear brakes and see in you are getting any pressure there. if you are not getting pressure there then you will need a master cyl. if you are you will have to follow the line down and check all the way back.

Master cylinder is more than likely bad. Try this: get helper in the driver seat, tell him to push on brake pedal and do not let up. Open the brake line at the master cylinder (crack it open) and see if fluid comes out. If no replace the MC! The rear line is for the rear brakes!

if you hear the fluid moving in the lines you have air. if you have abs, and you had the system open forward of the abs hydraulic control unit, there is air in it that you cannot get out. so if you replaced the reservoir and ingested air, or you had a leak elsewhere and ran they reservoit empty, or replaced a master cylinder or proportioning valve, you'll have air upstream. it will have to be bled with a scanner that can communicate with abs. most aftermarket scanners cannot. the build and decay valves and the pump motor has to be actuated, then manually bled again at the wheels to get the air out.

if it has ABS (make sure it does) it could be a stuck or blocked ABS actuator. You can "Hear" fluid going back through the master cylinder? you also might check to see if it has a load sensing proportioning valve to the rear. these can get out of adjustment (especially if the suspension is modified - is it?)

If you hear the fluid its because there is air in the line. If there is air in the line

1. seals

2. pin hole in the line

3. master cylinder.

See a mechanic

Take your vehicle to a professional,might have abs,failure,get it check out asap!