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Master cylinder issue


NAXJA Forum User
Hi folks.

My son's wheel cylinders blew out in the back of his 2000, and he let all of the brake fluid leak out before he noticed. We've already replaced all the brake parts and we're getting ready to bleed the system, but since all the fluid was gone, I pulled the reservoir and cleaned it, reassembled, and decided to "bench bleed" the master cylinder in place without actually removing it from the jeep.

My issue is, I have bled.all of the air out of the front port of the master cylinder (closest to the radiator), but the rear port is still steadily producing large bubbles. I think air is getting reintroduced to the system somehow, but I can't figure out how. the plastic bleed fitting seems tight, as does the clear tubing. the tubing ends are submerged in fluid. The reservoir is not completely full but at the full line, and the fluid doesn't seem to be going down anymore. What am I missing?

The mc has to be level in order to get all the air out! The prop valve may also be needed to be bled and to reset the piston.
Thanks RCP Phx for the response. I did eventually figure out that I used the wrong plastic fitting on that line. It was the right size but the wrong thread pitch and even though I had it screwed in tight, it was still sucking in air. I changed it for the finer threaded fitting, and it started to behave like I expected.

Brake job complete.