The truck:
2001 Ram 1500
5.2L engine
2 wheel drive
Rear ABS only
Front disk, rear drum

My truck was braking fine, but brakes started whining. Took a look and one brake pad was worn down. Upon further investigation, the caliper had seized up. So, I replaced the calipers with brakes and calipers from Kragen/Oreily.

Everything looked great. I bled the front brakes with a buddy the old fashioned way; him pumping the brakes and me opening and closing bleeder valve appropriately. Brake pedal felt firm.

Turned on the truck and the red brake light came on and the abs light too. The brake pedal went straight to the floor with little resistance. The back brakes are working pretty good, not sure if it is perfect or not though. I dont think the front brakes are working at all though.

I then used one of these
http://www.amazon.com/Motive-Product.../dp/B000Q6QWSC
to bleed the brakes. same thing.

Then I brought it to a shop. They bled it with 2 guys pumping the brakes the old fashioned way too. They bled the MC and all four brakes. Then the same thing happened, the pretty firm brake pedal went to mush when you turn on the engine. They said that it must be the master cylinder. I didnt think so because everything was fine before I changed the brakes and calipers. Well, I changed the master cylinder anyways, bled the brakes and the problem is still there.

What gives????

Is there a special way to bleed them? Why did the abs light come on if it is only on the rear brakes and I didnt open the rear brake circuit (at first).

 

your problem isnt air in the lines...

are you sure your not losing fluid from anywhere?
did you buy the correct calipers, are they making firm contact with the rotor?
are the wheel cylinder pushrods contacting the shoe?
are the rear brakes adjusted properly?

 

ABS light will come on if the switch in the proportioning valve trips. (I.E. Loss of pressure on either circuit, front/rear) Which is what turns on the brake light in the dash.... (if it isn't an ABS related problem..... they made that one nice and confusing.)

The brake pedal is harder to press when the engine isn't running, as you don't get any vacuum boost.

I wonder if you didn't blow out the rear brake line above the gas tank.

 

The back brakes seem to be working, they are adjusted properly and you can hear them functioning when i stand out of the truck and my buddy drives it around.

It does not appear to be leaking fluid anywhere.

Is there a special way to bled these abs brakes?

I really think the problem is with the front brakes. Is there something I have to do to the calipers since they were brand new? or can I just bleed them like normal?

 

No special tricks to bleeding. At least, there shouldn't be.

Rear line won't necessarily show fluid on the ground. It likes to pool on top of the tank..... and then drip off when you aren't looking.....

When you do front brakes, you have to pump the brakes up enough to extend the calipers such that the brake pads are contacting the rotors. (a firm brake pedal should be good enough for that, unless the pads were installed wrong.....)

Start the engine, can you pump up the brakes? If you can, if you pump them up nicely, and hold even pressure on the pedal, does it slowly sink?

 

with the truck running, I can pump the brakes to build up a little pressure but not too much. The pedal sinks faster than slowly, but not immediately.

 

I bled the brakes and even when the pedal is pretty firm, the calipers do not seem to be clamping down too hard on the rotors. why?

The rotors and brake pads seem to have gone on correctly, is there a way that I could have put them on wrong though?

 

You have a leak somewhere. Judging by the symptoms, I would start looking at all of the front brake lines, if those look good, might have gotten a bad M/C, or, maybe you didn't bench bleed it before install?

 

Sounds like a bad Master Cylinder.
Change it with a new one, not reman.
My truck did the same thing.

 

Brakes stopped truck ok but pedal felt mushy and holding firm pressure on the pedal it would go to the floor. First the red "BRAKE" light, immediately followed by the amber "ABS" light. If I turn off the truck, pump the brakes a few times in 10 seconds and restart the truck the lights would clear until I held the brake for 20seconds or more...

I replaced the master cylinder and bled all four corners until clear fluid came out. Still the identical problem. After reading up on it I was directed to investigate the anti-lock brake hydraulic module from an online fix site:

On the RWAL (Rear Wheel Anti Lock) module which sits 3" closer to the firewall than the proportioning valve, there is a rubber cap pointed horizontally right towards the master cylinder. Poke a paperclip thru the rubber cap about 1-1/2" until it touches the back of the RWAL accumulator piston. With key off, have a friend press and hold pressure on the brake pedal. If the piston moves, the service manual says to replace the RWAL. Mine moved, so the RWAL is supposedly bad. The only way for brake fluid to move the piston in the accumulator is for the anti-lock solenoid to be energized with battery voltage via the green wire on the "A" terminal of the connector... (OR if the solenoid valve is blocked open??, I thought.)

The leaking valve seat let fluid pass into the accumulator. The accumulator is spring loaded, so the "leak" doesn't go on the ground, rather it's collected in a spring loaded piston chamber and when you let off the brake pedal, the spring pushes the fluid back into the rear brake hydraulic lines & back into the master cylinder. Viola! Mushy pedal in spite of the following; brand new master cylinder, no air in system, fully bled system, NO visible fluid leaking under the truck.

My solution: My master cylinder reservoir was filthy with little black hunks of ??? in it. I suspected a chunk got caught under the solenoid valve seat during a hard stop yesterday, so with the key off/engine off I put 12volts to the green wire to energize the accumulator solenoid and repeatedly pressed the pedal to the floor and let it rest 10 seconds for a couple minutes. My theory was I could repeatedly fill and empty the spring loaded piston chamber of the accumulator and dislodge whatever might be blocking open the solenoid valve seat. SHAZAM! It worked...

If this problem comes back, I will do one of the following: Install a used RWAL module (new is big buck$) and powerflush all four corners again, or I will disconnect the rear brake lines from the RWAL module, connect them directly to one another, flush/bleed the system and effectively bypass the dang RWAL system.

...anyone need a used master cylinder that probably works just fine? It "only" has 246,200 miles on it.

Tom
Buford, GA