1997 with disabled ABS and a whooshing brake pedal

Stinkbug

Stinkbug

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I have a 1997 TJ that came with ABS. About a decade ago, I disabled the ABS by pulling the relay when I replaced my Dana 35 with a Dana 44 that did not accommodate ABS. The rest of the ABS is still in place. I have been running a 15” Big Brake Kit for over a decade as well.

I recently started having an issue with my brakes, they simply don’t break a well as before. It is most notable in 4 low. While it has always been expected and noticeable with heavy tires and 4.56 gears, it has become more and more noticeable on the trails and now the street.

The brake pedal is now spongy as if there is air in the lines and makes a “whoshing” sound as it is pressed.

So far I have bled the brakes starting a right rear and working my way towards the master cylinder. There are no air bubbles and I have clean fluid at each wheel. The discs and pads are in good shape and there is no sign of a leak at any of the calipers or connections.

Any thoughts on where to look next?
 
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Do you lose pedal after driving in traffic.. does the pedal get lower and lower as you drive more?
 
Stinkbug said:
I have a 1997 TJ that came with ABS. About a decade ago, I disabled the ABS by pulling the relay when I replaced my Dana 35 with a Dana 44 that did not accommodate ABS. The rest of the ABS is still in place. I have been running a 15” Big Brake Kit for over a decade as well.

I recently started having an issue with my brakes, they simply don’t break a well as before. It is most notable in 4 low. While it has always been expected and noticeable with heavy tires and 4.56 gears, it has become more and more noticeable on the trails and now the street.

The brake pedal is now spongy as if there is air in the lines and makes a “whoshing” sound as it is pressed.

So far I have bled the brakes starting a right rear and working my way towards the master cylinder. There are no air bubbles and I have clean fluid at each wheel. The discs and pads are in good shape and there is no sign of a leak at any of the calipers or connections.

Any thoughts on where to look next?
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You could have a couple things going n. The whooshing sound is probably the booster, I have seen boosters do this and work fine and other not work. Booster will cause high pedal effort.
Many ABS units have a small accumulator inside the unit like a spring loaded diaphragm and when the fail can cause a sponge pedal ( I’m not sure on the Jeep unit);
Have you checked or replaced the front pads? Here you tried the break in procedure again?
 
NskLJ said:
You could have a couple things going n. The whooshing sound is probably the booster, I have seen boosters do this and work fine and other not work. Booster will cause high pedal effort.
Many ABS units have a small accumulator inside the unit like a spring loaded diaphragm and when the fail can cause a sponge pedal ( I’m not sure on the Jeep unit);
Have you checked or replaced the front pads? Here you tried the break in procedure again?
Click to expand...

Pads and rotors are good at all 4 corners and I am familiar with the need to get on the brakes pretty hard on occasion to keep the BMB brakes working at full capacity. It’s the spongy pedal that I think might be related to that whooshing sound when the brakes are applied that is giving me grief.

I have read that some newer vehicles (maybe all) have a special procedure to bleed the ABS portion of the system. But I have never heard of it regrading an early TJ.
 
Stinkbug said:
Pads and rotors are good at all 4 corners and I am familiar with the need to get on the brakes pretty hard on occasion to keep the BMB brakes working at full capacity. It’s the spongy pedal that I think might be related to that whooshing sound when the brakes are applied that is giving me grief.

I have read that some newer vehicles (maybe all) have a special procedure to bleed the ABS portion of the system. But I have never heard of it regrading an early TJ.
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I know at ford we would hook up a scan tool and run the bleed procedure that would cycle the abs valves then bleed it normally. We had the issue on 2wabs where it had a small accumulator that would just make a soft pedal no matter how much bleeding was done.
Do you have normal pedal effort?
Have you pulled back the master to see if it’s leaking into the booster?
 
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Rickyd said:
I know it isn't really helping your issue but i used this kit on my 97 to delete the abs. It fit well with a few little adjustments

https://www.inlinetube.com/products/sjpb9701

did you see the recent soft pedal thread by @AndyG ? Could be some ideas in there?
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In my opinion inline tube makes some great stuff. My son and I repiped his 1970 during a full restoration. There were a few things that were not right on the rudimentary evap system and after a few pictures and back and forth the sent some new tubing to correct the issue.

I have thought about pulling out the ABS but am not sure what else is involved and this problem may serve as the catalyst to doing it.

I will check out Andy’s thread and see what I nuggets of wisdom I can find there.
 
I swapped in the tube kit and put the right fitting in the rear of the prop valve where you have a plug now.thats all you need besides removing the fuses and abs relay. Works great. I got the fitting from a similar vintage grand cherokee if i remember right
 
Rickyd said:
Post in thread 'Project Basketcase!' https://wranglertjforum.com/threads/project-basketcase.67755/post-1258270
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Thanks - I took quick look and will add that to my list.. it made me think a bit about my proportioning valve… it has been years since I replaced the rear end with a new axle with discs and I don’t recall ever making a change to it. Since it has been so long I doubt that it is having any effect on the braking woes I am now having. But that might be something to investigate once I have this problem squared away.
 
Artsifrtsi said:
Do you lose pedal after driving in traffic.. does the pedal get lower and lower as you drive more?
Click to expand...

I missed this one… I don’t notice it in daily driving unless I really hammer the brakes in a hard stop. The amount of hammering required is getting less and less. It is more obvious when on the trails and working the brakes. They get spongy and work their way closer to the floor with each application of the brakes. They have never not stopped.
 
NskLJ said:
Do you have normal pedal effort?
Have you pulled back the master to see if it’s leaking into the booster?
Click to expand...

This is why I asked that. Mine had a leaky master, and there was a lot of fluid that had leaked into the booster. Driving in traffic, it felt normal at the start of a trip, but driving across town, the pedal would slowly get softer... at stop lights as the brake system heated up, the pedal would slowly move to the floor, eventually (on excessively long lights) the Jeep would even start to roll, pumping up the brakes helped. When I pulled the master, the fluid had made a mess of the inside of the booster, and I replaced both.
 
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