My car is a four door LX, rear drums, non ABS.
This fall I believed I had a failing brake booster. My brakes would work normal sometimes and other times I would need to pump them. I never knew when to pump so somtimes I would give too much brake and end up looking like a newby driver.

I performed a booster check that was outlined in my Chilton manual as well as a vacuum check valve test. check valve passed, booster failed.

I thought I could live with it a bit more. But once winter set in, locking up the brakes when the booster worked, proved dangerous on ice.

So I bought a new booster. Along with it I bought some pads and shoes and drum brake hardware. I figured I might as well while I was at it.

Installing the booster was no fun, but I did it. And afterwards my brakes felt great. I drove around the block a few times and it seemed as though I fixed my problem. Nothing feels better than that. I was lovin it!

I pulled into my garage and performed the booster test again to be sure. The first step is to depress the brake pedal several times to make sure there is no change in pedal height. Well, while doing that, all of a sudden, the pedal gives and goes to the floor. Urrrg!!! No pedal!!! I start the car, try pumping, and I get nothing!

Long Story... please stick with me.

After sleeping it off and doing more research i inspected some things.

No leaks to be found, under car or under hood.
I cracked open the drums and replace the shoes and hardware.
Found a bad wheel cylinder on the drivers side, so I rebuilt it.
Started to bleed the system.
started at the rear drivers side, then front passenger, then front driver.
at the front driver, no fluid or air would come out unless I had my assistant continually pump the pedal.

at that point I stopped out of frustration, cold, and a broken finger.

my plan was to try and bleed from the passenger rear today. and maybe figure out how to adjust the rear brakes without taking the wheels off. My manual says something about an adjuster located on the inboard side, underneath the control arm. I'm not sure what the inboard side is... Hopefully it will be clear once I look at it.

Anyway, I'm kinda stuck just stabbing at things. I'm learning as I go. I'm thinking that I have to adjust the rear brakes, bleed all the air, and possibly flush the brake lines somehow? Alot of IDK's. Fluid being bled is also very very dark and dirty.

Please, the more ideas and suggestions. the better. Gotta baby coming this spring and need to get my car back on the road.

Thanks

 

...need to pump brakes to stop (but it will if you do)...pedal (sometimes tending toward always) goes to the floor...->bad master cylinder.

There's no reason for me to believe you ever had a problem with the booster. Bad boosters do one of two things, neither of which you have experienced. Either the pedal is very hard to press-- but the car will stop without the pedal going to the floor, or (uncommonly) the brakes slam on at the slightest touch of the pedal. Again the pedal does not go to the floor.

 

ok, just some questions though...
would I be able to still pump fluid out the bleeder screws by using the pedal if the master cylinder was bad?

also, I inspected the "push rods" between the booster and master cylinder for brake fluid, indicating a leak and bad master cylinder, and found everything to be shiny clean and dry.

also, I'm not loosing any fluid. Wouldn't a faulty master cylinder leak into my new booster and the fluid level in the reservoir go down?

And when i did change the booster, everything seemed fine for a bit. and my pedal never went all the way to the floor until I tested it again.

and what about the bad wheel cylinder I found. is it possible that I had more pressure after changing the booster which resulted in blowing out the seals and boots in the wheel cylinder, thus letting air into the system?

I just checked to see if my parking brake that use to always work, would stop the rear wheels from turning when applied. I pulled up like 11 or 12 clicks and only got a tiny bit more drag.

maybe i do need a new master cylinder, but i feel like there may be more involved.

 

Yeah sounds more like a bad master cylinder.

There's a good chance that with a bad master cylinder, you may not get all of the air out of the system when trying to bleed it. If an internal seal is bad, you may not have enough pressure to get all of the air out. You should replace the master cylinder and then bleed the system. You'll have to anyways after you replace it. Which you should ASAP because if the master cylinder completely fails, you won't have brakes at all and you and anyone around you is f**ked.

The master cylinder has seals inside of it. If a seal inside the master cylinder goes bad, you'll lose brake pressure. Just because the cylinder is bad doesn't mean it will leak externally.

Again, a bad master cylinder seal internally would likely have no visual signs. So you wouldn't see any fluid leaking around the cylinder and the fluid level shouldn't change.

You said that you replaced the rear brakes? You have to be careful when changing the rear shoes. If you tear either of the 2 rubber seals around the wheel cylinders or open the cylinder up, contaminants could easily get in and ruin the wheel cylinder.

After replacing the shoes, did you adjust them at all? If you didn't, that may explain why your e-brake engages so late. If you did adjust them, you may have brought the shoes in too far. Adjust the shoes until the rear brakes have a tiny bit of friction when you spin the drum over them and also bring the e-brake handle up and make sure it clicks only a few times, not 10+..

And yes, definitely sounds like a bad master cylinder. Replace it ASAP.

 

Yeah it sounds like a bad master, what can happen is the internal seals in it fail and fluid leaks past the piston that forces fluid to the wheel cylinders resulting in no pressure but no leaks as well. I had the same problem with my A/C Beetle (only simpler to diagnose) Try replacing the master and see where that get you.

MC

 

Thanks a ton people. That puts me on a better track I think. I was under the impression that there would be definite signs of leakage. I will the replace the master cylinder asap.

The wheel cylinder on the driver's rear was bad, so I replaced the seals and boots, and made sure to keep everything clean.

What I hate is to think that I wasted money on a booster I didn't need.
Do you think that a new booster was enough to finally kill a master cylinder that was on it's death bed?

Anyway, thanks again for the knowledge and help.
Should have checked here first before all the wasted time, money, and broken finger.

 

Just put a new master cylinder in and all is good. in fact after all the new parts, the brakes are better than ever. ya... imagine that... one bad thing though, now my parking break doesn't work.

The rear drums are adjusted properly. I tried to adjust the slack in the p-brake cables and found that the passenger side cable wont budge. So I took off the pass. side drum and took a look. Everything moves freely that should. But the cable seems to be frozen. so I used some rust blaster stuff and sprayed the two ends of the cable and waited. Still frozen. I don't understand this because it worked before and I swear I installed the shoes and hardware correctly.

Does anyone have any ideas? Should I just replace that cable? If so, how much of a pain is that?

Thanks for your help.

 

The cables can rust up at any time. They are not hard to replace but you will have to get under the car. To release the outside of the cable from the brake plate, push a box end wrench (I think 12 mm) over it to push in all the spring clips at once. Then it will pull out of the hole. I'm not sure how the end at the handle inside the car comes apart but it should be obvious once you take the plastic trim off.

 

OP, if you want to save, just buy the repair kit for the master cylinder.

 

My problem is similar to yours. I bought the car monday of last week, front brakes went out on thursday while driving in Folsom, my brother replaced the rotors and brake pads on Saturday. I drove to Reno, NV on Sunday and the distributor went out, no spark on Monday, going great so far! Hghhh Tuesday the guy Im dating helped me put in a brand new distributor. Sick on wednesday, drove home thursday, got home just fine. Woke up friday and drove to my appointment only for the car to start screaming at me when I came up to the stop sign, the brake pedal seemed to stick similar to when a gas throttle sticks. I actually lifted it up with my foot, then I applied the brake again and it went down to the floor board, I pumped the brake lightly and it came back up. Then it continued to scream at me. Car drives fine but it screams. What could this be? Has anyone ever experienced this before?