Mushy brake pedal, no matter what.

[DeCaff2007]

More like it goes right to the floor, engine off.  Still goes to the floor with minor resistance, engine on. 

76 T/A with rear drum.  All factory stuff, no upgrades.

There's no leaks and the fluid is topped off. 

Everything bleeds pretty easily except for the front driver side.  Really have to pump that pedal to get anything to move (not forcefully, just the fluid moves really slow).

Regardless, I can bleed the brakes all day and the pedal will not stiffen up. 

I thought perhaps the brake booster is bad (long story there) and I can hear *some* whooshing upon pedal press.  However, I was under the impression that a bad booster would cause a hard pedal with no movement. 

Also, I just got the proportioning valve unstuck this morning.  Turns out it was blocking off the front brakes.  I was able to free up the pressure differential valve and blew air through both front and rear sides.  It's now clear as a bell.

Any suggestions?

[FormTA]

WTF? You're alive! Man, good to hear from you! I have had bad Master cylinders right out of the box...

Is the masters cylinder original? I can't remember if you changed that years ago.

[roadking77]

Good Reaction Luke! DeCaff! Its like a long lost brother has come home. I am sorry I cannot help with your brake situation. I am just about to tackle the brakes on my car. May be a dumb question but did you bench blead the Master? As Luke mentioned could the master by bad? When they did my 77 the first 2 (1 I got from inline tube, the other Napa) were bad out of the box. When I called inline they said it was the mechanics fault, Napa replaced the bad one I got from them and the third one worked perfect. I did have problems not long after the initial install with the pedal going to the floor. Turned out there was a fitting that was not perfectly tight, BUT it was not leaking. Maybe check to see if everything is socked up properly.
Anyway good to hear from you.

[DeCaff2007]

WTF? You're alive! Man, good to hear from you! I have had bad Master cylinders right out of the box...

Is the masters cylinder original? I can't remember if you changed that years ago.

Yes I'm alive and hello, FormTA, roadking77.  I'm surprised you all even remember me.

The MC is aftermarket junk that I purchased locally YEEAARRRSS ago.  It wasn't even a direct fit as it is adjustable.  Made in china garbage that actually bears the Delco Moraine stamp. 

EDIT:  I meant the vacuum booster, not the MC, sorry. 


Bench bled?  Likely yes. 

Yes, all fittings are tight.

I'm too old for this lol.

[FormTA]

How could we forget you? You could fill this forum with what you've be up to

[DeCaff2007]

How could we forget you? You could fill this forum with what you've be up to

That would violate several forum rules, I'm sure.

So, I'm reading that a failed vacuum booster will cause a hard pedal.  How so?

[FormTA]

Just a educated guess,  but with no power assistance you don't the leverage or strength to push it. Just a guess though.  Or maybe when they fail they lock up?

[DeCaff2007]

Well, between this forum and evil social media, I have a new MC on order.  I've also ordered a new brake booster because I just don't like the one that's in there now. 

We  shall see what happens.

[FormTA]

Make sure you double check the booster fitment.  The first one I got from autozone (I think that's where it came from) had the wrong ange to the mounting brackets and the MC would have hit my hood if I didn't notice it.

[ryeguy2006a]

Welcome back man! Same exact thing happened to me and it was a combination of a bad MC and stuck proportional valve. Hope you get it straightened out!

[DeCaff2007]

Welcome back man! Same exact thing happened to me and it was a combination of a bad MC and stuck proportional valve. Hope you get it straightened out!

I checked the proportioning valve, too.  It indeed had blocked off the FRONT brakes.  Not anymore!  Weird part is, I was still having a hard time pushing brake fluid through the front brakes. 

I don't mean excessive force on the pedal, I mean having to pump it many, many times to get anything to flow.

[scarebird]

YOu still have air in the lines.  Gravity bleed thoroughly - we are talking at least a quart run thru.

[DeCaff2007]

YOu still have air in the lines.  Gravity bleed thoroughly - we are talking at least a quart run thru.

Yes, that's fine I'll do that.  Now I have another question.

Does anyone have a more effective way to turn the bleeder screws on the REAR brakes?  A 5/16 combination wrench can just BARELY fit in there.  Well, as I go back and forth to loosen/tighten as my old man pumps the pedal, the wrench just gets looser and looser on the bleeder screw.  Eventually, I have to reposition the wrench to hopefully get a better grip on things. 

This is a with a 6 point combo wrench. 

Actually, I would upgrade to rear disc as I have all the parts to do it, EXCEPT for the fact that I've already ordered the new MC for rear drum. 

[aussieta]

maybe time to replace the flexible lines
2 to front and 1 at diff
are the back brakes assembled and adjusted correctly
i recently found my car had incorrect low drag calipers on the front

[DeCaff2007]

maybe time to replace the flexible lines
2 to front and 1 at diff
are the back brakes assembled and adjusted correctly
i recently found my car had incorrect low drag calipers on the front

The rear brakes... been through ALL of that.  I don't think I have the correct parking brake cables (they seem too short and won't connect to the front cable), but that won't affect the brake pedal. 

Rubber lines could be a culprit.  We'll see what happens when the MC/Booster comes in.

[DeCaff2007]

It's done!  The new master cylinder and brake booster...  then bleeding the brakes until the cows came home....  did the trick.

I now have FULL pedal and the car stops like the day it left the factory.  Now, I have to get the correct connector and switch for the proportioning valve so the BRAKE light will illuminate correctly if there's ever a problem.

Thanks guys.

[FormTA]

Glad you got it working. I wonder which one was the real problem though.  My bet is on the master cylinder though....

[scarebird]

Actually, I would upgrade to rear disc as I have all the parts to do it, EXCEPT for the fact that I've already ordered the new MC for rear drum.

I have found that master will work just fine on rear disc too.

[FormTA]

Really? I had a tough time finding the aluminum 81 disk master cylinder for my car when I swapped to the 4th gen. I love the feel but I am concerned if and when I have to replace it that it will be impossible to find.

[79GoldnTan]

Great, glad you got it figured out. Super glad to see you are still around. Hoping you and yours are all well. Keep on keeping on!