Brake issue and diagnosis help

[SBarber1]

History:
Needed to replace brake booster. While replacing noticed fluid in resvoir was very dark and it looked like there was sludge in the bottom of it. There was black slude when i scraped it, a lot. I replaced master cylinder as well just to be cautious and bleed entire system. (Bench bleed master cylinder) Everything worked well for a couple weeks.

Issue:
Last week started jeep pushed brake pedal in the morning when I was about to back up and it went almost to the floor with little to no resistance. Brake light on dash came on and was flashing and beeping. Looked at resevoir and the fluid was clear but had a dark gray tint to it. I figured I screwed up the bleed and didnt flush all the old fluid and air.
Baught a brake bleeder from harbor freight and flushed the entire system again and was very confident that I fixed the issue. Weired part was I flushed out and collected what appeared to be almost the same ammount that was put back in. I tested the brakes and they were dont soft or spongy at all better than they had been ever that I could remember.
Worked great all last week. Jeep sat over the weekened and again monday morning pedal went straight to the floor and alarm went off. Fluid was clear but gray again and fluid resevoir was full this time as well. Jeep is able to stop so I drove around the neighbor hood for awhile pumping brakes and testing. Resevoir never went below full line.
When jeep is on brake goes soft and alarm goes off. If i pump brakes slowely while stopped the alarm and lights will sometimes go away. If i turn it off and pump brakes it will firm up after a couple pumps.
Driver side front line is pitted and rusted in one spot next to wheel well were it was rubbing. It doesn't appear to be leaking but im going to replace anyways.

Im going to bleed again tomorrow and meassure what comes out vs what i put in. Dont think its a fluid loss issue.

So vacuum leak or what else?

Why is fluid turning gray, old hydraulic lines or what else? (Orderd and going to replace as well.)

 

[Steel City 06]

That doesn't sound like a brake booster failure. A brake booster failure would generally revert to manual brakes, meaning the pedal would get stiff and less responsive, not spongy and easily floored.

When you flushed the fluid, did you recycle any of the old fluid back in? (You should never reuse fluid.) Did you flush until the fluid came out clear in each caliper?

If there is a fluid leak, often you would notice a small pressure loss. If you hold the brake pedal down for a period of time, dies the pedal get softer? That could indicate a leak.

 

[SBarber1]

That doesn't sound like a brake booster failure. A brake booster failure would generally revert to manual brakes, meaning the pedal would get stiff and less responsive, not spongy and easily floored.

When you flushed the fluid, did you recycle any of the old fluid back in? (You should never reuse fluid.) Did you flush until the fluid came out clear in each caliper?

If there is a fluid leak, often you would notice a small pressure loss. If you hold the brake pedal down for a period of time, dies the pedal get softer? That could indicate a leak.

Correct I know it is not a booster issue. I replaced the booster because it was starting to make a really bad hissing noise that drove me crazy.

No I did not resuse any fluid.

Yes I flushed tell it came out totally clear from each calipar and kept going tell resevoir was completely refreshed as well.

When wrangler is off and i push pedal hard tell it stops i dont notice any drop after that.
If I keep the same pressure on the pedal and start it up pedall goes straight to floor.

I flushed with one large jug. Put the old fluid back in the jug and it appeared to be about the same volume which leads me to beleave there is no fluid loss.

 

[williambmac]

Drum or disc in the rear? do you have ABS?

 

[CharlesHS]

The dark sludgy substance looks like old contaminated brake fluid or something is decomposing.
Do a thorough inspection of the rubber and hard brake lines, the caliper and wheel cylinders, proportioning valve; there is something that isn't responding properly in your brake system.

 

[SBarber1]

Drum or disc in the rear? do you have ABS?

Disc Front
Drum Rear
No ABS

 

[williambmac]

are you sure the shuttle valve in the proportioning valve (combo valve) isn't stuck?
You need to center the shutter valve and then try to re-bleed.

I stole this from an older post. Thanks @mrblaine

What is very easy to get stuck closed though is the shuttle valve in the combo block that shuts off the front or rear brake fluid circuit when there is a higher differential pressure on the other side of it. The valve has a detent in it that locates the shuttle valve evenly between the front and rear circuits. The spring loaded plunger at the end of the switch you see on the side of the combo block holds it in place until one side has a low pressure situation that indicates a leak. When that happens, the higher pressure moves the shuttle valve and limits flow to the low pressure side.

If you stomp the pedal a few times and it doesn't reset and turn off the brake light on the dash, then something is making it act like it has a leak. That can be a leak or lots of air in one end. (can't check the brake light on the dash with the parking brake applied)

I would stomp on the pedal until your brake warning light goes off and use the help of a friend or pressure bleeder to correctly bleed the system.

 

[SBarber1]

So this is what the fluid looks like after 2 weeks on second flush. Looks like maybe coroded rubber particles in fluid?

 

[SBarber1]

The dark sludgy substance looks like old contaminated brake fluid or something is decomposing.
Do a thorough inspection of the rubber and hard brake lines, the caliper and wheel cylinders, proportioning valve; there is something that isn't responding properly in your brake system.

Wheel cylinder looks like might be the problam.