Brake Problems

[Jae 'Bird]

I've got an issue, I just finished re-doing the rear drum brakes as the old wheel cylinders blew. I also replaced the rearmost brake lines as they were rusted. I did everything correct, I think, and then it was time to bleed them, which is where the issues started. I of course started with the right rear as it was farthest from the master cylinder. I was bleeding it using the two person method and it was going ok but I was confused because I was getting micro-bubbles and they didn't seem to go away, I even tried using grease to "seal" up the threads to make sure it was closed up, I saw someone on the lube tube do it. Long story short I get about the same thing with all four wheels and when I started the car, the brake pedal was super mushy, I assume the micro bubbles are not ok to have right? I'm just making sure, and second, would air be coming in through the bleeder threads? is that possible. Lastly, would a power bleeder tool help to get rid of the micro bubbles that seem to be my issue? Thanks for the help in my predicament.

 

[theterminator93]

I've found that bubbles tend to form in the drain hose that gets attached to the bleeder screw when I use a power/vacuum bleeder, but not when having a helper depress the pedal. So if you're still getting bubbles, there's more bleeding to be done.

I suspect, however, that your rear brake hardware may just be out of adjustment, leaving a gap between the shoes and drum which leads to a terribly mushy pedal until the shoes and drums make contact. Double check to be sure the self-adjuster mechanism isn't gummed up or stuck, then try and "open it up" a little to take up the bulk of the slack. When you apply and release the brakes while in reverse it's supposed to trigger the adjuster screw, and take up slack incrementally as the shoe linings wear.

 

[MadMikeyL]

How long was the system opened? If it was open long enough to completely drain the master cylinder, then you may need to bleed the master by itself first. Also the drum brake cars had a diagonal split system, so you may need to bleed the front brakes as well. I would start by bleeding the master, then bleed all four wheels.

 

[Grog6]

It's 20 year old fluid too, do a gravity bleed first, to replace all the fluid in the lines. A gravity bleed is where you open all 4 bleeders, and run a quart of fluid thru them. (I start with a quart bottle of new fluid, and let it drain thru until it almost fills the beer bottles I keep for that. clear glass bottles work best, you can see just how bad the crap you're draining. After I almost fill them, while I still have some left in the bottle, I do the classic 2 person bleeding. Replacing 20 yo fluid is important. Make sure not to let the master reservoir go empty during any part of the process.