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Bleeding brakes problem...can't get air out

DanZ

NAXJA Forum User
Can someone help me out here please

1996 Cherokee Sport

My pedal goes right to the floor.

I am bleeding the brakes. I blocked off lines coming from the master cylinder and the pedal is rock solid. I just blocked off the rear and the pedal hits the floor again. So there is air in the front brakes. I bled them several times at each wheel and the master cylinder but the pedal is not getting better. If I pump the brakes and build up pressure I have a pedal but as soon as I let the pressure off and try it again it goes to the floor.

Any suggestions? I am pretty sure it must be air in the lines somewhere that just won't come out from normal bleeding. Does anyone know someone with a pressurized brake bleeder or have any other ideas?

I am really stuck here.

Thanks
 
How are you bleeding them?
 
I personally like a vacuum bleeder. I made one using a surplus medical vacuum pump and a mason jar. The vacuum on the lines causes the bubbles to expand, making them easier to extract.

Back to the problem, you may have a rubber brake line that is ballooning, but most likely you just still have a major air bubble. I have seen the problem you describe be a leaky master cylinder. It doesn't seal real well until you build up some pressure. When you block the lines, it instantly builds pressure due to no fluid movement, where as with the pistons that have to move in the wheels, the pressure does not build as quickly.
 
I spent a few hours at it tonight again. Tried sucking fluid out with a big syringe, same problem. Even though we don't think there is anything wrong with the MC, we took it off and dissasembled it anyways since we were totally stumped. All the cups look fine with no grooves or visible wear anywhere.

Only guess is that there is still air in the lines somehow?
 
Try your normal bleed, pump three times then release the bleeder at the caliper, then holding the pedal to the floor, until the bleeder valve is re-tightened. If you release the pedal before the bleeder valve is retightened you just suck air back into the system. *unless you do this*
Get a piece of tubing that will fit over the end of the bleeder and will reach all the way to the ground, put it in a glass jar, put enough brake fluid in the bottom of the jar to cover the end of the hose. Bleed it (like mentioned above) until all the air is out (you can see the bubbles). Save the glass jar and hose for next time.
Don't let the reservoir go dry. If the reservoir goes dry, you sometimes have to bleed the master cylinder, the piston stack can get shoved together, with little or no fluid between two pistons.
If it has ABS it's a whole nother can of worms, you have to bleed the ABS, before bleeding the wheels. Don't even try it with the power on.
Are you getting fluid out of the front bleeders? And then no brake pedal?
 
I have speed bleeders on my 98, makes the job a bit easier as they close by themselves, then when you are done you tighten them up all the way. Reminds me, need to order that pressure bleeder and a different colored fluid this winter, I want to completely change the fluids in all three jeeps and the oldsmobile this spring.
 
Did it have pedal before you started working on it? If you did, I'd guess the master cylinder needs to be bled.
Getting all the air out of the master cylinder can be a pain, sometimes it goes easy and sometimes it takes a lot of work.
 
try cracking the fittings on the master cylinder one at a time,just crack have someone slowly push pedal to see if air comes out. Do both lines see if that helps badge714
 
DanZ said:
pump bleeding with two people
This does not describe procedure.

If your assistant is pumping the peddle a lot, the fluid is becoming aerated and you'll never get the air out. Also, you have to be certain that your assistant holds the peddle down until you close the bleeder, then let the peddle up. All peddle movements should be gradual, not rapid.
 
Thanks for the help guys.


turned out they gave me two right side calipers and therefore the bleeder was on the top on the pass side and on the bottom on the driv. side. Partsource was all out so i just turned the driver's side caliper upside to bleed it so the bleeder was on top. Then reinstalled on the rotor. All is good now.

Thanks again
 
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