No brakes

[WickedXJ]

So just some background first on my brake system, recently, new front calipers, rotors, pads, and steel braided lines. New rear axle with new lines and steel braided extended line. Complete fluid swap done about a two months ago. Okay so now that you guys have some background to work with my brake don't work. Well when the Jeep is cold and I start it up for the first time in a day or two I can drive it around town and maybe like 10 miles to a wheeling spot and the brakes seem fine. Then I will drive home a few hours later and I literally have little to no brakes. I can pump the pedal to get some pressure in the lines and get some braking but nothing even close to the amount of pressure that I should be getting. I can also get the brake pedal to the floor, with very little pressure, and then it sort of stops and I can stand on the pedal and it will kind of brake. There was some fluid lost a little while ago but I can't figure out why. I have done nothing and yet the fluid seems to have stopped leaking. I drove it to the CCSU car show and that is when it got it's worst. The brakes were all there and good as I can remember up until I got on the highway, which is about 10 to 15 minutes from my house. Then I drove 50 minutes on the highway without touching the brakes, I can't go fast enough to need them anyway. Then when I got off the highway they were basically gone. I left the Jeep parked in a VERY hot parking lot for about 6 hours then started it up again and the brakes were just as bad all the way home. I also checked the fluid this morning and it seems really brown and not clear. I really want to drive my Jeep more but I cant because of this stupid issue so please guys help me figure this one out.

[grundlepunch]

when you put new rear line in, did you route it close to the exhaust? boiling your brake fluid?

[WickedXJ]

when you put new rear line in, did you route it close to the exhaust? boiling your brake fluid?

nope tried to get everything as close to stock location as possible. I also just went out and looked and they come no where near the exhaust.

[jeepbogger4x4]

Are you losing fluid at all from any of the connections or a pinhole in one of the lines when you step on the pedal?

[WickedXJ]

Are you losing fluid at all from any of the connections or a pinhole in one of the lines when you step on the pedal?

No. I think I have narrowed it down to the BMC as when the vehicle is off I can still press the pedal to the floor and it is now happening cold or hot so I'll pick one up at NAPA tonight and see if it fixes it.

[Hydra]

Sounds likely, a hole in the diaphragm would cause cavitation

[CumminsJeep]

i vote booster. fluid can leak into there and maybe when its getting hot it doesnt like it. if the lines arent broken and no leaking calipers/wheel cylinders, i would immediately go to the booster if you are loosing fluid mysteriously.

[WickedXJ]

Pretty sure it was the BMC. I put a new one in today after a 4 hour run to Napa...long story, got pulled over 3 times and stuck in traffic for 2 different accidents, holy fail....Napa is 15 minutes away. Anyway I got the old one out and the new one bench bled and in but by that point I was being eaten alive by mosquitoes so gave up and I will fully bleed the system tomorrow and have an update. On a related note can I buy a compete fully flared line that goes from the proportioning valve to the BMC or will I have to buy some brake line and ends and bend and flare it myself?

[customcreationsllc]

just flare it yourself you should get a flaring kit you will need it.
You can only buy standard ends on a hard line unless you can find a specialty brake line place. But napa will have a kit of every end you need if you cannot reuse your old fitting. You might be able to find an adapter so you don't need to flare.

Did you change the MC the first time? A way to check that would be to install plugs if the peddle is as hard as a rock you MC is good.

If you booster goes bad you have a very hard peddle not soft when you say you have no brakes is the peddle hard or soft/ goes to the floor.

double check all your connections easy to have air suck in you don't always see a leak. are you getting air when you bleed?

Make sure you installed the calipers on the correct side bleeder screws on the top.


Think of brakes as just a master piston hose to a slave piston not very hard concept.

[WickedXJ]

Yes it was the master cylinder. Bled the brakes today and took it out for a drive and it actually STOPS now. The Pedal is still a little mushy so I foresee some more brake bleeding in my future as I gave up on one tire because it was stripped so I'll have to get a new bleeder and fix it. But the pedal doesn't go to the floor anymore so with a tiny bit more work she will be ready for wheelin again.