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Air in master cylinder? Bleeding issues.

96xj_twood

NAXJA Forum User
Location
SC, USA
I emptied the reservoir of most of its brake fluid a few months ago with plans to swap my master cylinder before my XJ hits the road again after a big repair project. I put the cap back on when I was done removing fluid.

I've since decided that my master is probably fine and my brake system issues were caused by overheating due to my over tightening of the new shoes I installed.

So I put on new calipers and rotors, and want to evacuate all the old fluid. But the brake pedal is not pumping up and holding any pressure for me to start bleeding the system.

Would an empty'ish reservoir with the cap on allow air into the master and have created this problem? No cracks or damage on the cap. The seal looks to be fine as well but im no expert.

Should I just pull the master and bench bleed it?

Or could I use a pneumatic bleeder kit from Harbor Freight and straighten this out?

I don't have anybody to work the pedal for me so I was just trying to pump up the brakes and shove a board in between the pedal and seat. Then I found the pneumatic bleeder kit and thought it may help me do this easily by myself. But i'm not sure how good it is going to work if I have gotten air into the master cylinder.

Any suggestions? Thanks for reading.
 
Or you may be able to fill the master, crack a few bleaders or all of them and walk away for a while. See if it will gravity bleed even if its only enough to get it going.
 
Or you may be able to fill the master, crack a few bleaders or all of them and walk away for a while. See if it will gravity bleed even if its only enough to get it going.
This is what a buddy suggested. Seems way easier than pulling the master all the way off.
 
I just did mine and I used a pipe one end on the pedal and warped a bungee cord around the steering wheel and hooked to the other end of the pipe. Open bleeder then close, then pull pedal up and repeat.
 
two options for not pulling the master and bench bleeding.

buy speed bleeders (worth every bit of the $10 a pair they cost)
or buy a vacuum bleeder. The HF air compressor powered one works well if you have a compressor large enough to power it, and it's cheap.
It's replaced my legitimate mighty vac unit as my go to for brake bleeding.
 
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