Ok guys need some help on rabs units on broncoII's (anti lock) . Here is the prob the brake pedal goes to the floor when the rig is started by its self. This is one of my snow plows and it gets used only for plowing I was going thru the normal start up for this rig and had a clutch master cylinder leaking so replaced it and was giving it a short run down the road. Everything was working well till i stoped and the brake went to the floor. Rabs lite is on and blew a front break line. Can unplug the vac booster and the pedal comes back but still no breaks can the rabs valve be causing the booster to compensate for the rabs valve in a stuck position? The brakes were rebuild last season with all new cylinders and pads,cables,hardware ect. checked the master to see if it was stuck and its fine so iam at a loss on this one ????

 

It sounds like you're on the right track. Unfortunately, I am not qualified to offer suggestions about brakes.
As soon as Ken00 finishes his cleanup work on the "Technical Information" thread, you should have a look in there for RABS info. If you don't find it in the BII tech thread, look in the one on the Ranger board.
AL.

 

Here's an old post of mine if it's any help.

If ou need to troubleshoot the RABS here is an old post of mine that might help.
You may have a leaking RABS dump valve. Locate the valve(usually on the frame rail under the drivers foot. Identify which valve you have either square or round(most likely round) If it's square: Locate and remove the small rubber cover at the end of the RABS valve. Straighten a metal paper clip and insert it into the hole covered by the rubber cap until it bottoms out. While watching the paper clip have someone firmly apply the brake pedal. If the paper clip moves at all the dump valve check ball seat is leaking and you must replace the RABS valve. There also should not be any fluid at all that runs out when the rubber cap is removed. If you have the round valve(larger). Use a 1 1/4 box end wrench and remove the end cap from the valve. there is a spring under the cap but it doesnt have a great deal of pressure on it. You can easily control the end cap while removing it. Visually observe the piston inside the area covered by the cap or place your finger near the end of the piston( dont press on it). While having someone firmly apply the brakes check for any movement of the accumulator piston. If it moves at all the dump valve is leaking and you need a new RABS. No fluid should spill out when you take the cap of either. There is also a possibility that you wont have these access ports on your vehicle. Did the fromer owner replace the Master? If so did he bench bleed it? If he didnt that could also be the problem
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