On a 2005 Dodge RAM 1500 SLT 4.7L, the ABS Hydraulic Pump/Modulator may have failed, as indicated by the dump valve wire test. Brakes work but the pedal slowly sinks to the floor while braking. All four disc brakes have been bled. The ABS pump has been bled at the pump's exit brake fitting to rear discs with a second complete bleed. No ABS or Brake warning lights are on. No codes have appeared by the ignition key test. On hard test stops, there is a momentary stall before braking, which could be the pump activating the ABS. The ABS is probably a Kelsey Hayes RAWL ABS: one line in and one line out. Stalled on this for now and have three questions:

1) Is there a reputable vendor for rebuilt ABS pumps? Or a rebuild service?
2) Is it worth separating the ABS pump from the electronic module and cleaning both with electronic parts spray cleaners?
3) Is there a $200 scanner that will do ABS bleeds for the Dodge RAM 2005?

Thanks for any help! Sykes

 

If you only have RWAL, then I think all you have is a dump valve, no pump. (I might be wrong though, your truck is newer than anything I have played with.) If the pedal is slowly sinking to the floor, that indicates a leak somewhere, or possibly a bad master cylinder. Pull the vacuum line off the brake booster, see any brake fluid in there?

 

That would make sense as the ABS unit is really small and I see no DC pump motor. There is an electronic module with an inline plug, so that must be activating the dump switch? I put a wire into the vent cap and on depressing the brakes, the wire is pushed out indicating dump valve failure. I am isolating the master cylinder tomorrow and will check for brake fluid in the vacuum lines. The pedal holds until the vehicle is started and running. If it wasn't the ABS, I could resolve this job no problem. Thanks!!!

Good write up on dump valve test at page bottom: Vented Cap Screw Design (Rear Wheel ABS "Block Style"
https://www.brakebleeder.com/diagnos...les-rwal-rabs/

 

Engine running provides vacuum assist for the brakes, and that makes a BIG difference in pedal effort. Try turning the engine off at about 30mph, and trying to stop. Better have LOTS of room.

 

I live out in the country - plenty of runway for road testing and 30mph hamburger turns. I do have to rule out the master cylinder and vacuum. Bypassing the ABS is supposed to show whether the vacuum and MC will hold the pedal. That's next.

 

Bled the brakes through twice. Replaced the Master Cylinder and no change. Pads and rotors are in spec. There has been no ABS or brake light warning indications. No fluid in the vacuum. 'Hey You' is right that this ABS is just a dump valve, accumulator, and isolation valve. No DC pump. Just module monitoring for ABS rear wheels. The dump valve fails the wire test every time. While driving, the brakes work perfect for tap stopping, unless foot slightly depresses the pedal which then slowly sinks to the floor. I am going to inspect disc pistons, but I’m sure the problem is this two brake line ABS pump. Talked to a mechanic, and they suggested electronic module and master brake cylinder, so will just stay the direct route and take a gamble with Ebay, the only place I could find an ABS pump replacement.

For now, a scan tool may help with diagnosing, but it seems that no scan tool will auto bleed an early ABS like this.

I will be pressure bleeding the present ABS pump through the two disconnected lines, attempting to clear any debris, as I have nothing to lose trying. Thanks

ABS Pump Modulator and Electronic Module. Master Cylinder brake line in and rear brake line out. Visible fluid is from bleeding. White rubber cap is the dump valve seal.