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-   -   2002 WJ Limited - Brake pedal travels to the floor (http://www.jeepgarage.org/f199/2002-wj-limited-brake-pedal-travels-to-the-floor-65613.html)

StephenE 09-17-2013 11:30 PM

2002 WJ Limited - Brake pedal travels to the floor
 
I had to brake hard to avoid someone who decided to turn at the last minute in front of me. Now when I press the brake pedal it travels almost to the floor. I have replaced all four calipers, all rubber lines with braided stainless and the master cylinder last year. I took the Jeep to have the brakes looked at today and they thought it was the master cylinder, so they replaced it. After bleeding the brakes, the pedal still travels to the floor when pressed. They tried another new master cylinder and it did the same (pedal travels to the floor after bleeding the brakes). The only items I have not replaced in the braking system are the booster and ABS module.

Has anyone else had this problem? Thoughts?

Frango100 09-18-2013 02:12 AM

Re: 2002 WJ Limited - Brake pedal travels to the floor
 
The booster will not cause the pedal to go to the floor, only internal/external leak or air in the lines will cause that.
When the jeep is standing still and you press the pedal several times, does that make any difference? If it does, then for some reason the brake pads are pushed back too far after braking when driving, causing the need of more fluid to apply them again and consequently the brake pedal will go deeper then normal or even to the floor.
When you brake when driving, do you feel any vibration or pulsation in the pedal, which could indicate a warped disc?
Eventually the ABS controller could be faulty. It was probably activated during the heavy braking which you mentioned and maybe one of the valves is halfway stuck, dumping the pressure to the reservoir. You could look for a DRBIII scanner or any other scanner which could access the ABS controller, to activate the valves and maybe reset the stuck one or flush away any dirt which could hold it open.

StephenE 09-18-2013 10:54 AM

Re: 2002 WJ Limited - Brake pedal travels to the floor
 
Quote:

Originally Posted by Frango100 (Post 895442)
The booster will not cause the pedal to go to the floor, only internal/external leak or air in the lines will cause that.
When the jeep is standing still and you press the pedal several times, does that make any difference? If it does, then for some reason the brake pads are pushed back too far after braking when driving, causing the need of more fluid to apply them again and consequently the brake pedal will go deeper then normal or even to the floor.
When you brake when driving, do you feel any vibration or pulsation in the pedal, which could indicate a warped disc?
Eventually the ABS controller could be faulty. It was probably activated during the heavy braking which you mentioned and maybe one of the valves is halfway stuck, dumping the pressure to the reservoir. You could look for a DRBIII scanner or any other scanner which could access the ABS controller, to activate the valves and maybe reset the stuck one or flush away any dirt which could hold it open.

Thanks Frank.
Pressing the pedal several times does nothing. There is no vibration or pulsation while braking. A DRB III scan tool is out of my budget. I read somewhere that I can remove the ABS relay and activate the pump by shorting two pins in the relay socket.

Anyone ever buy a used ABS pump from a junkyard? Would an ABS pump from the junkyard be reliable?

Frango100 09-18-2013 11:32 AM

Re: 2002 WJ Limited - Brake pedal travels to the floor
 
I did not mean to say to buy a DRBIII, just to look for a garage who has one, or a comparable scanner, so that the ABS can be tested.
If you can find a used unit from a junkyard I would say why not. If it looks clean and undamaged from the outside and is packed in plastic to prevent foreign material to get in(when it is already removed from the vehicle), it should be ok.

StephenE 09-18-2013 06:53 PM

Re: 2002 WJ Limited - Brake pedal travels to the floor
 
Frank,
I purchased a used ABS module and installed it. After bleeding the brakes at the ABS module and at each wheel cylinder (in proper order) I have brakes that feel and behave like normal. I am only out $79.97 for the used ABS module and brake fluid plus a few hours of my time.

I will update this thread if there are any new developments.

Thanks for your help Frank.

Frango100 09-18-2013 10:53 PM

Re: 2002 WJ Limited - Brake pedal travels to the floor
 
Good to hear that the problem is solved.
Did you change the complete assy, which consist out of the HCU (hydraulic control unit= valve unit) and the CAB (controller antilock brake= electronic controller)? The manual calls for reprogramming the CAB when it is changed, but i have no idea what the programming does. If you could find a place with a DRBIII scanner, then you could test the ABS and see if it performs ok.

StephenE 09-19-2013 01:09 AM

Re: 2002 WJ Limited - Brake pedal travels to the floor
 
Frank,
I changed out both the CAB and HCU. A few preliminary tests in gravel indicate that ABS is working. I currently have less than 1 inch pedal travel until I feel the brakes grab. If I can find someone with a DRB III scan tool I will ask them to run the ABS test.


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