Originally Posted by wellmax
one time I when through 2 or 3 rebuilt master cylinders on my 1984 cj with power brakes, before I got one that worked properly.
I was using advance auto, I would just take them back and they got me another one.
I bench bled the master cylinders using the inserts and short tubes provided with each kit. used the handle of my ratchet or screwdriver to pump the master cylinder, had to make many pumps until the bubbles stopped.
then installed the master cylinder and all was good,
once I got a good master cylinder.
brakes on a old jeep are marginal at best, power brakes make it much better.
I had this similar problem with Auto Zone masters. I have read where several of the guys went through this as well. Wish we still had the old days when you could buy a rebuild kit for $3 and do it yourself!
Originally Posted by Msmall
I do need to do the power brake upgrade. Part of the reason I've put the minor bubbling on the back burner.
I also want to k so what is going on with this. It seems like when the brakes are engaged and the rod is pushed into the master that it is forcing air in. As it e rod is catching air when out and then pushing air in when engaged.
Your concept is good, but one of the steps in bleeding a master is to make sure it is level. That's where a vice and a level come in handy. I suppose it is to ensure bubbles aren't trapped in pockets inside the body. Wipe the master off really well, depress your brake pedal slowly to avoid squirting, and watch for leaks. If your plunger is grabbing air you will be losing fluid at the rear of the master. It could be running down the inside of your firewall as well as outside. If you don't have evident leaks then I think you should try bench bleeding again. Use shorts strokes on the master, not long ones (don't know why, just what the directions say to do!). You could really use a second set of eyes, if you don't already have them. It takes a LOT of strokes to get the air out.