Braking issue

Jellymon said:

The other day I replaced my left rear caliper, bled all 4 brakes twice now with no bubbles, and never let the master cylinder run dry. I also have no leaks anywhere I'm able to physically see.

So my issue is that while stopped with engine running I'm able to press the pedal to the floor with a little effort. Braking starts immediately after pressing the pedal, and feels normal with enough power to activate the ABS. It doesn't go near the floor while normally driving/braking, it just feels soft when I'm stopped. When the jeep is off the pedal is very firm and only goes down a couple inches.

With some research I'm seeing that the most common cause for this is a bad master cylinder, or air in the lines. I've ruled out air in the lines with 2 bleeds with zero air, so I'm just wondering if what I'm seeing is normal for a JK before I go out and replace the master cylinder. I appreciate anyone's :twocents:. Thanks.

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WJCO said:

Sounds like a master to me as well. At any point during the brake repair did you push fluid back up through the system? If fluid is dirty enough and pushed back through the system, I have seen master cylinders and abs units damaged. Doesn't mean it happens every time, but I've seen it happen.

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Jellymon said:

The other day I replaced my left rear caliper, bled all 4 brakes twice now with no bubbles, and never let the master cylinder run dry. I also have no leaks anywhere I'm able to physically see.

So my issue is that while stopped with engine running I'm able to press the pedal to the floor with a little effort. Braking starts immediately after pressing the pedal, and feels normal with enough power to activate the ABS. It doesn't go near the floor while normally driving/braking, it just feels soft when I'm stopped. When the jeep is off the pedal is very firm and only goes down a couple inches.

With some research I'm seeing that the most common cause for this is a bad master cylinder, or air in the lines. I've ruled out air in the lines with 2 bleeds with zero air, so I'm just wondering if what I'm seeing is normal for a JK before I go out and replace the master cylinder. I appreciate anyone's :twocents:. Thanks.

Click to expand...

DogHouse said:

You said it takes a little effort to to push the pedal to the floor. I would say that sounds normal, you probably just never paid attention to it before the repair. I can push my brake pedal to the floor using about 30% of my leg strength while sitting at a light (same thing in my wife’s Liberty). I should also add this is after two caliper swaps and a pad change. I’ve never had any issues in the two years since these repairs.


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Jsouder53 said:

Just curious, how would fluid get pushed back up through the system? I’ve never heard of this before, I want to make sure I don’t accidentally do this...


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WJCO said:

When you collapse the caliper to install new pads. If you don't open the bleeder, the fluid goes back through the master cylinder. If you open the bleeder, the fluid comes out right near the caliper without causing any disturbance to the rest of the system.

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WJCO said:

When you collapse the caliper to install new pads. If you don't open the bleeder, the fluid goes back through the master cylinder. If you open the bleeder, the fluid comes out right near the caliper without causing any disturbance to the rest of the system.

Click to expand...

WJCO said:

Sounds like a master to me as well. At any point during the brake repair did you push fluid back up through the system? If fluid is dirty enough and pushed back through the system, I have seen master cylinders and abs units damaged. Doesn't mean it happens every time, but I've seen it happen.

Click to expand...