This has probably been addressed a thousand times before. I've searched and read several threads here as well as on other forums but cant seem to find what I'm looking for, so hopefully you kind folks can help.

Background:
I bought my 76 in April 2014. It had spongy brakes but it stopped well enough, so I drove it off and on till fall (not the best idea, I know that now). One night I noticed the pedal went almost to the floor before the car stopped, so I parked it for the fall/winter. I finally dug into the brakes a few months ago and found the left rear caliper was leaking, so I replaced it and put new pads on the car all around. The others appeared fine. Nice and dry. I bled the car as best I could, but the pedal never felt very firm. Still pretty spongy. I thought I simply had done an inadequate job bleeding the system, so I finally decided to pay a shop to do it, just to rule out my own incompetence.

The brakes still feel spongy. They're a little better than before, but the pedal goes halfway to the floor before the brakes even Start to grab. Once I get stopped, there is only about 1/4" to 1/2" of travel left before it's at the firewall. Now maybe maybe I'm expecting too much, but I think I should have a lot more pedal than that.

I've read that there's a rod in the Booster that actuates the piston in the MC... perhaps that is somehow improperly adjusted? Or maybe something to do with the vacuum fitting on the booster?

I've read several times on this forum, and others, that when everything is right the pedal is "rock hard" and the brakes can "throw you through the windshield." Maybe that's an exaggeration, but still. I just want good brakes so I can move on to other things. I can't well do much with a car that won't stop reliably. What am I missing here?

 

With the master cylinder lid off gravity bleed the brakes again; giving each bleeder screw about 5 minutes of bleeding time to ensure all of the air has been purged. Be sure to keep the master cylinder near full during the whole bleeding process. Then when you're done park it on a steep incline with the nose pointing down and apply the brakes about 10 times to purge the air out of the nose of the master cylinder. You should end up with a hard brake pedal.

 

The master cylinder is actuated by the booster through a pushrod, which needs to be a specific length. If someone before you has done a replacement of either booster of cylinder, then you may have to check the length of this pushrod.

But... I'd try all easy options first!

 

I am having the same issue with my '77. I have bled the MC and brake lines alot and still have spongy or no brakes at all.

 

I played with this for years . had changed everything but the booster. was turning the car off . I leave it in gear with my foot on the brake because other wise I get pre ignition . as the engine shut down I noticed that the brake pedal started putting pressure on my foot . I changed it the other day now I have brakes real good brakes . only thing was I got the booster from napa and they said it was a exact replacement . I have a real high brake pedal and no way to adjust it down . but have pretty much all ready got use to it .

 

it goes without saying, but just in case, you didn't really put oil in the system did you? oil or petroleum products will swell and destroy the rubber components in the brake system. Always use brake fluid...not trying to be offensive, but you said leaking oil, and I've seen people do this very thing. take the cover of the MC off and the gasket is swelled up like a balloon...

 

I should gravity bleed again? Even after having a shop use their super-special pressure flush machine?

where can I find the information for the correct pushrod length? I'm at work (on lunch) at the moment so I can't check my shop manual, but I assume it'd be there, correct?

There's not one mention of oil in this thread, prior to your post. Not sure where you got that idea...

Thanks for the help guys. While it's hotter than Satan's buttcheeks here and my car doesnt have A/C, I'd still rather be driving it than my DD. Got to get this brake problem figured out.

 

To the top.

Any more responses? So far I have suggestions to re-bleed and to check the brake booster pushrod length. Anything else? I'd like to look over everything at once instead of doing it piecemeal.

Thanks.

 

I'm in the same boat as you. I replaced my LR brake caliper yesterday. I did not bleed the system. I replaced the same caliper 7 years ago. I had a motive brake bleeder (one man job) and bled the system. It worked. I do not have it anymore (the plastic bottle cracked) I have not tried the "gravity bleed method" As for the suggestions you received, there is noting piecemeal about it. Based on what you described, it is obvious that air is in the system. As for the suggestion about checking the pushrod length, you can do it but more than likely. it is at the proper length and it will be a real pita to readjust it. IMO that would be the last thing I would do.

Try bleeding the system again. You can also replace the bleeder screws with those that have a check ball in them (commonly known as "speed bleeders" available at your local auto parts store) They prevent air from being sucked back into the calipers.

Is/was your brake warning light on when you discovered the leaking caliper? Was the MC fluid level low on either reservoir?

 

The push rod in question was discontinued for 77. For up to 76, take the two nuts off that hold the master cylinder to the booster and pull it away, you will see the push rod. It's simple to adjust, but be warned that if you get it too long the master cylinder will not release all the pressure and the brakes will drag and get hot.

 

All I can tell you is I tried everything and never got a decent pedal. Honda Civic brakes were far superior. I bought a Motive Bleeder. Went around the car twice. Super easy and fast. Used low pressure. Good pedal for the 1st time and haven't touched them since.

 

actually, the original post specifically stated "left rear caliper was leaking oil"...I didn't make that up.