69 Barracuda 318, brake pedal sags

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56Steve

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Hello,
My 69 Cuda brake pedal sags and keeps my brake light on. I have to pull it up to keep it off.
Any thoughts, I just put new brakes and brake lines on it.
Thanks in advance for any thought's.
Steve
 
56Steve said:
Hello,
My 69 Cuda brake pedal sags and keeps my brake light on. I have to pull it up to keep it off.
Any thoughts, I just put new brakes and brake lines on it.
Thanks in advance for any thought's.
Steve
Click to expand...
Did you replace the master cylinder?
 
Wondering if the pedal is actually low or the switch needs to be adjusted. Take a look at the switch and see if you can adjust it a bit. The master cyl is what holds the pedal up, if its actually low you could be looking at a master issue or possibly the wrong rod from the pedal to the master. Also make sure the bolt that holds the rod to the pedal is tight and correct. Its a shouldered bolt. Did it do this before you did the work? Check the easy stuff first!
 
340doc said:
Wondering if the pedal is actually low or the switch needs to be adjusted. Take a look at the switch and see if you can adjust it a bit. The master cyl is what holds the pedal up, if its actually low you could be looking at a master issue or possibly the wrong rod from the pedal to the master. Also make sure the bolt that holds the rod to the pedal is tight and correct. Its a shouldered bolt. Did it do this before you did the work? Check the easy stuff first!
Click to expand...
 
I did replace everything, It had no brakes.
Thanks, I will take a look under there.
 
>If you can put a toe under the pedal and manually return the pedal to the top of it's travel, and if the brake-lites then go out,;then the brake-lite adjustment is correct. If you then remove your toe, and the pedal flops down, then it's a pushrod adjustment solution.

Pushrod adjustment
>It's the springs inside the M/C that return the pedal to it's proper parked position,via the pushrod.The clip at the top of the M/C bore, keeps the piston from traveling too far, and coming out. So it's parked position is engineered in. And so you have to synchronize the pedal's parked position, to the M/Cs parked position.

>Assuming the pedal-bushings are free ,If the adjustment is too short, the pedal sags. This will show up, immediately after a new install
> It's also possible that the pushrod started out too long. Then the Compensating port was closed. Then, over time the pedal drops, as the pads or shoes wear, and compensating fluid is never introduced. This will begin to show up weeks after a new install.

>Hang on there is another possibility.
Inside the M/C, after the guts are installed, are three chambers. Two of those are for pumping fluid out to the slaves, and the third chamber is between them. If this chamber is full of air, then it is theoretically possible for the weight of the pedal to push the rearmost piston ahead until it hits the backside of the front one. Of course if it did that, it would take the pushrod with it, and then the pedal would also sag. The result of this, if the frontmost piston is plumbed to the front brakes, would be very poor braking as only the rear brakes would work.
If you suspect this, you will have to figure out how to fill that inter-piston chamber with fluid. This is most easily done by bench-bleeding it with one end slightly elevated, and watching for the air bubbles to finish escaping from that chamber thru the compensating ports.
 
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Had same issue. Turns out it was just the brake pedal switch that needed adjustment. super easy.
 
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I just had the same thing happen after replacing all front brakes, master cylinder, along with all hard and soft lines. I just found the brake light switch bracket and bent/pushed it towards the brake pedal lever. Problem solved
 
Mikey Yoh said:
I just had the same thing happen after replacing all front brakes, master cylinder, along with all hard and soft lines. I just found the brake light switch bracket and bent/pushed it towards the brake pedal lever. Problem solved
Click to expand...
Solved for now!
What happens if a brakeline bursts? and you run out of pedal before the back-up system even comes on line.
I mean think about it; peoples lives are at stake!
 
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AJ/FormS said:
Solved for now!
What happens if a brakeline bursts? and you run out of pedal before the back-up system comes on line.
Click to expand...
Whoa .... it was an eighth of an inch of adjustment! I swapped from drum to discs which required a different master cylinder; which required an adapter. So, yeah, solved forever.
 
Thanks for all of your help!!
I have been considering a disc brake conversion, is it difficult and pricey?
Thanks in advance!
 
56Steve said:
Thanks for all of your help!!
I have been considering a disc brake conversion, is it difficult and pricey?
Thanks in advance!
Click to expand...
I used a kit from Dr. Diff. Pretty easy to do. The way I look at it is that stopping is more important than going; well worth the money.
 
Mikey Yoh said:
Whoa .... it was an eighth of an inch of adjustment! I swapped from drum to discs which required a different master cylinder; which required an adapter.
Click to expand...
Mikey,
if your pedal is parked up against the factory stopper, then ignore the rest of this post.


But if you,(or anyone else reading this post),have a floppy pedal that does not park up high on it's factory engineered stopper, then read on.
> that ain't right. On a properly working system,If one end fails, the pedal will drop nearly to the floor.That is normal.
>If it's the front system that fails and you have lazy, out-of-adjustment rear drums,that pedal will be just about right on the floor, and the rear brakes would seem not to be working, in addition to the missing front brakes.
>If it's the rear that fails, the pedal will fall to a somewhat higher position,but still close to the floor, but I can almost guarantee that when it happens, you will panic and start pumping the brakes, never even stroking it to the bottom, and you will likely crash.
Now factor in a floppy pedal, that doesn't activate the front brakes until the pedal is right on the floor, and repeat these words;
"So, yeah, solved forever".
If you doubt this, go crack the rear brake-line, with someone else operating the pedal,and see how far the pedal drops.
This is just for If you have a floppy pedal, with the M/C pistons properly parked internally..
 
AJ/FormS said:
Mikey,
if your pedal is parked up against the factory stopper, then ignore the rest of this post.


But if you,(or anyone else reading this post),have a floppy pedal that does not park up high on it's factory engineered stopper, then read on.
> that ain't right. On a properly working system,If one end fails, the pedal will drop nearly to the floor.That is normal.
>If it's the front system that fails and you have lazy, out-of-adjustment rear drums,that pedal will be just about right on the floor, and the rear brakes would seem not to be working, in addition to the missing front brakes.
>If it's the rear that fails, the pedal will fall to a somewhat higher position,but still close to the floor, but I can almost guarantee that when it happens, you will panic and start pumping the brakes, never even stroking it to the bottom, and you will likely crash.
Now factor in a floppy pedal, that doesn't activate the front brakes until the pedal is right on the floor, and repeat these words;
"So, yeah, solved forever".
If you doubt this, go crack the rear brake-line, with someone else operating the pedal,and see how far the pedal drops.
This is just for If you have a floppy pedal, with the M/C pistons properly parked internally..
Click to expand...

Thanks for your response.
 
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