RustyRacer

My friend and I have been trying to get the brakes to work for a few hours and we're stumped. It bleeds great no air, or atleast seems as though theres no air. The brake pressure builds up nicely. Then I turn it on and press the brakes and it goes right to the floor. There is vacuum in the booster because I pulled off the hose and it went pshht. Is it maybe the rod from the booster to the master cylinder or is there maybe a problem in the master cylinder? Maybe something missing?

Scott1982

1) Have you recently replaced the master cylinder or has this been sitting?

2) If you just replaced it - you likely have air in it - do a search on bench bleeding - you must fill the internals before you install or it will be full of air.

3) If you havent just replaced it, likely it is rusted and fluid is going past the seals - look around - do you see fluid anywhere?

4) You can double check the mech connection to the pedal - but I would think that is okay - never no though...


Scott

orion84gsl

iTrader: (5)

I would say you are loosing pressure in your master cylinder. New one isn't too expensive. Or get a rebuild kit for the one you have, cheaper but more involving.

yetterben

I am haveing the same issue although with a new master!

RustyRacer

1. Yes I replaced it a few months back, and it wouldn't build pressure at all.
2. We bled the top and side, slightly pulled off the lines and bled those too.
4. It builds up pressure but when I turn on the car and hit the pedal it goes right to the floor. I'm thinking something about the pin that goes into the MC isn't adjusted properly, but how do I know if its less than a millimeter from the MC? Maybe it is the vacuum?

Scott1982

The only way I can think of for the pedal to go to the floor is that you have air in the master... That is the first problem to address, I don't believe you can generate enough vacuum to floor the pedal with full hydraulic capability (unless you have a leak).

When engine is off (no vacuum), can you put your foot to the floor on the brake pedal? You must be able to given what you have described...

http://www.misterfixit.com/brakbld1.htm


Scott

RustyRacer

I did the bench bleed when I got it, though I don't know if I did it that well. I can push my foot to the floor when the car is off. I also don't know if I have the brake pedal connector rod at the right length, I have to push it in a bit maybe a 2 or 3 mm to get the pin to slide into place. The pedal doesn't really stiffen to the point I can't press it anymore, but it does get better than when the car is running.

Okay I went out to the car, with the engine off I pressed the pedal and it built a little pressure, but I also heard a huffing sound coming from the booster by the pedal. I put RTV around the booster when I installed it.

I was reading on another web page that the internal seal could be bad.

Scott1982

Not sure what internal seal you are referring to - but your master is either bad or needs bleeding. Since you said you put in on a few months ago - I should assume it is new (or was it from a donor?)

Not that hard to take apart if you have done a wheel cylinder. 9 times out of 10, just cleaning them is good enough although rebuild kits aren't expensive. When you put it back together, put fluid in there, helps the bleeding.

Scott

RustyRacer

Well, I did what you suggested Scott. the second piston had a chip but a burr was kinda catching on the wall. The seals looked great. I'll be doing the big bleed tomorrow morning. The plunger off of the BB comes out nicely, but it doesn't want to go back in on the dowel straight on. Can that be adjusted?

Scott1982

Not sure what the BB (Brake Bleed?) is? If plunger does not go one cleanly, find cause, should be fixable. Picture?

Scott

RustyRacer

Sorry, brake booster. When I press the brakes it goes fairly smoothly, then it gets tight, then lets go and goes to the floor. Binding on the brake booster?

Scott1982

Huum, never fiddled with one of those... Maybe someone else can chime in?
You have the master cylinder off, and the pedal motion is not smooth through the booster? Sounds like you need a new booster?

Scott

RustyRacer

Sweet, my dad and I went and worked on it. I bled the hell outta the brakes and the front passenger was chock full of air and old brake fluid. Don't always trust your friend I suppose. Gonna eat breakfast and try it out. It kinda slips slowly, so I'll magically get it to the garage so they can do a full bleed of the system. Thank you very much Scott. Have a great day, I know I will.

blackdeath647

iTrader: (2)

i would have told you it was air if i would have read it before :P, i had the same problem and it took me about 1.5 hrs of bleeding, (forgot to bench bleed it, i'm glad i didn't screw anything up) but it's working properly now....never trust friends haha, that's why i get them to sit in the car and press the brake, i do the rest lol.

Scott1982

Happy to see you have it going again!

RustyRacer

Wow, that was quite an experience. Hit the brakes and it shifts to the right, then to the left then straightens out and gets mushy. I don't think I'll be taking it in quite yet as the funds are kinda low right now. Probably needs pads, rotors and drums. I'll just keep tinkering with it. Thanks for the help.

axle

check pads and shoes now and manually adjust them the auto adjust doesn't always work the greatest on these old cars

RustyRacer

Got a little greedy and drove it, got about 3/4 to H so I turned it off and coasted for a while. No chocolate in the oil, so I don't think it went bad. Cooling system next week.

Scott1982

You can likely rebuild the calipers and slaves for little $, just takes some time. It will be worth it to have all good stopping equipment so that it is smooth and pulls evenly. No worse than what you just did with the master. Although, calipers always make me use foul words when rebuilding them. Pads cost < $20 auto autozone, have not priced shoes as they always seem to be okay (cause they dont adjust so well)

Scott

badfun

I just changed out my MS and having the same problem I guess I need to bleed them some more? I did a bench bleed before i installed.