Changed the brakes on my 2000 Jeep Cherokee. Did the rear first took it for a test drive and had brakes. Did the front end and now I have no brakes at all, in any way shape or form....
Thought it was the master cylinder so I replaced it not once but with 2 different master cylinders. Also found a small vaccuum leak which was then taken care of. On top of that found out that the seals in the Break Booster were shot so went ahead and replaced that....

I have bled the everything several times, for what seems over like 200 times now, and yes I did bleed it the correct way, also did bench bleed the master cylinder... There literally is no air in the lines at all.

We can pump the brakes up and it will get extremely stiff when it's turned off, the second we turn it on we loose all of the brakes and it goes right to the floor... No ABS and even checked all of the fuses for the sh*ts and giggles.

The rear shoes have been adjusted as well as the weird two way bolt behind the master cylinder...

Thinking it may be the proportioning Valve? But those are super rare to go bad I've heard....

I'm already $1000 deep into this thing so the sooner this is fixed the better...

 

Knee deep in drum parts myself right now so I'll be following along

 

Air, bleeders not up.

 

Pumping the brakes up with it not running is just depleting the vacuum until you can't overcome the pneumatic resistance of the booster. Starting it and the brakes going to the floor is your proof of that.

When you said "no ABS" did you mean it's not equipped with ABS or there is no ABS fail light illuminated? If it has ABS, you likely still have air in the ABS pump. The will give you "no pedal" and it's hard to get the air out of the pump.

Also, don't believe you can't get two bad master cylinders, especially if they are rebuilt units. I've bought three in a row before getting a good one.

If it's not equipped with ABS, I'm leaning toward another bad mc. Are you getting good fluid flow at every wheel while bleeding?

 

The jeep is not equipped with ABS. Also both of the master cylinders were brand new, didn't even bother to go with a remanufactured one. And yes I have good flow to every wheel, can't hear any air coming out of the lines either when it has been bled.

 

did you change the front calipers?
you could have them on the wrong sides. bleeders have to be above the brake line. i'm sure this is the problem.
you will never be able to bleed the air out of the lines when installed wrong.

this goes for the rear wheel cylinders also.

it's easy to mix these up. many have done it before so don't feel bad.

 

I am not for sure that I have ever heard of this, but even if this is the case, I don't see this causing zero petal at all

My suggestion would be to take it to a shop specializing in brakes. More than likely they have not only seen this before, but have probably fixed it a ton of times as well.

 

I would be with other guys. if you changed the calipers check that they were not put on upside down. I have done it. Also if you did not change the calipers check that the cylinder is not cocked in the bore causing it to not move. It will still bleed nice but will not move when you hit the breaks.

 

if you're interested watch this. he says from the beginning he made a mistake but you can see the trouble he's going through to figure it out, and he indeed has no pedal. could very well be the issue

at around 30-31 minutes he figures out the problem and explains it. in a nutshell, bubbles raise at the top. if your bleeder is at the bottom air will never escape the system.

 

There are only a few things that will allow the brake pedal to travel to the floor;

1. Excessive travel of piston in caliper or wheel cylinder caused by mis-adjustment of drum brakes or something broken, missing, or misassembled in drum brake or caliper.

2. Fluid passing around piston(s) in master cylinder.

3. Mechanical defect in brake pedal linkage to master cylinder

4. Air in hydraulic system.

Seems from the info, you must have 1 or 4. Once you verify the possible swapped caliper issue, I would bleed through a tube run into a jar of fluid. You can see any air escaping.

 

Front calipers have been changed yes, and they are on correct I have run out of ideas and yes I did try them all. Went to a brake shop to make sure I did everything right. Which they said I did do. They even did a diag on it and can't figure out the issue. They rebled the lines and did another bench bleed still no air. They took the rear end apart and redid it all over and Got a very minimum amount of brakes but ended up disappearing so We're thinking it may be the Wheel Cylinders... They checked and rechecked the master and the pvalve with no leaks.. Gonna do the cylinders tonight and go from there. Will check back in after doing it.

 

I can sympathize with your frustration. I can only offer this. Did you adjust your parking brake after you did the drums? Did you adjust the drums with the star wheel? Correct brake fluid and NEW never opened? My real confusion is that you had brakes after the rear was done and then none at all after you did the disc in front.

 

Yes parking brakes were adjusted. Everything has been adjusted and bled not once not twice not even ten times but literally 50+. Replaced the Wheel Cylinders last night, as those were completely shot. As well as the gasket on the proportioning valve was bad. That was also replaced. The brakes are now getting hard with the vehicle turned on. But they wont stay hard. Have some braking under 30mph. Anything over and the brakes disappear. Thinking its the master cylinder. We rechecked the Proportioning valve; no leaks its working the way it should, so we are at a loss right now. But I refuse to let this thing win...

 

The following is a quote from a forum. Maybe try one more MC and use this method?????? Also put a piece of 2X4 under the pedal when you bleed again to prevent full travel.

"One thing is that after brake pad replacement is that the pedal should be pumped with small pumps, like 1/4 stroke, when you fully stroke the pedal, the master cylinder seals go across a ridge built up in the cylinder and this ridge damages the seals, thats why you didnt have any problems until you replaced the pads".

 

Any updates? Would love to know what it was