Newly installed aluminum master cylinder spongy brakes

[74bronk]

So did what previous guy suggested removed all Teflon and even bench bled , bled all 4 wheels .. no more foam looks good . Question what are the symptoms of a bad booster, or failing booster? I’m just not thrilled with the brake pedal. vehicle stops but just feel the pedal “should”be stiff as a horse c..k

 

[Brush Hog]

Probably just need time to get used to the feeling of power brakes. Just like upgrading to power steering it works just makes the job easier.

 

[El Kabong]

So did what previous guy suggested removed all Teflon and even bench bled , bled all 4 wheels .. no more foam looks good .

Good. Sounds like you're one step closer.

Question what are the symptoms of a bad booster, or failing booster? I’m just not thrilled with the brake pedal. vehicle stops but just feel the pedal “should”be stiff as a horse c..k

To me vacuum assisted brakes never feel as stiff as manual brakes. Think of it like someone else stepping on the brakes with you when you do. It doesn't feel the same to you because someone is doing part of the work. How does it stop compared to before?

As far as symptoms of a bad booster, I've always heard a "Whoosh" whenever the brake was applied on a bad one. Sometimes it's quiet & you can't hear it from the driver's seat, but with my head under the dash & applying the brake by hand I've been able to hear that vacuum leak.

If the pedal is too low, the 2 main factors (once all air is out of the system) I've seen have been adjustment of drum brakes & length of the rod from booster to M/C. A tiny adjustment on that rod can make a big difference.

Are your self adjusters working? With the drum off you should be able to give the cable a little tug & see the adjuster pawl climb up the star wheel, then the pawl turn the star wheel downward when you release the cable. If it doesn't spin the wheel you need to free it up by cleaning & lubing the threads. Also confirm that by turning the outer side of the starwheel downward it should make the adjuster longer. If it gets shorter the adjusters are reversed left & right.

Self adjusters operate when you back up, step on the brake, then let off the brake. Each series of on & off moves the starwheel one tooth, so it can take awhile to dial them in. I back up & step on & off repeatedly quickly until the vehicle stops. Then do it again several times.

Once the brakes are adjusted correctly the cable doesn't move enough to pull the pawl up until the brakes wear down some.

2 questions: Have you tried partially applying the parking brake then seeing how the brake feels? What method are you using to bleed the brakes?

 

[ksagis]

Some maybe obvious things to help get air out - I’ve had luck in tapping on calipers, etc to help promote bubble migration, and also temporarily “pulling” flex lines down to eliminate high spots and bubble traps.

In super bad cases, going as far as removing calipers, putting a block to simulate the rotor, and making bleeder the absolute high point.

 

[Wild horse 75]

Bad rubber hoses can cause a soft feeling pedal. Incorrectly adjusted drum brakes can also create a low soft pedal. I’ve found when a booster fails either you’ve got a vacuum leak that you can hear or the pedal is rock hard cause there’s no assist and you’re fighting the internal spring in the booster. Power brakes will always have a softer pedal feel than manual brakes. Some are worse than others. Almost every GM I’ve ever owned has a soft spongy pedal. And there was nothing wrong. Still stop like a hot damn but just a crappy pedal feel. If the truck stops like it should you might just have to learn to live with the pedal feel.

 

[74bronk]

Bad rubber hoses can cause a soft feeling pedal. Incorrectly adjusted drum brakes can also create a low soft pedal. I’ve found when a booster fails either you’ve got a vacuum leak that you can hear or the pedal is rock hard cause there’s no assist and you’re fighting the internal spring in the booster. Power brakes will always have a softer pedal feel than manual brakes. Some are worse than others. Almost every GM I’ve ever owned has a soft spongy pedal. And there was nothing wrong. Still stop like a hot damn but just a crappy pedal feel. If the truck stops like it should you might just have to learn to live with the pedal feel.

Can anyone else confirm that about GM power boosters? Cause basically that’s what I have on my bronco.

 

[74bronk]

Good. Sounds like you're one step closer.


To me vacuum assisted brakes never feel as stiff as manual brakes. Think of it like someone else stepping on the brakes with you when you do. It doesn't feel the same to you because someone is doing part of the work. How does it stop compared to before?

As far as symptoms of a bad booster, I've always heard a "Whoosh" whenever the brake was applied on a bad one. Sometimes it's quiet & you can't hear it from the driver's seat, but with my head under the dash & applying the brake by hand I've been able to hear that vacuum leak.

If the pedal is too low, the 2 main factors (once all air is out of the system) I've seen have been adjustment of drum brakes & length of the rod from booster to M/C. A tiny adjustment on that rod can make a big difference.

Are your self adjusters working? With the drum off you should be able to give the cable a little tug & see the adjuster pawl climb up the star wheel, then the pawl turn the star wheel downward when you release the cable. If it doesn't spin the wheel you need to free it up by cleaning & lubing the threads. Also confirm that by turning the outer side of the starwheel downward it should make the adjuster longer. If it gets shorter the adjusters are reversed left & right.

Self adjusters operate when you back up, step on the brake, then let off the brake. Each series of on & off moves the starwheel one tooth, so it can take awhile to dial them in. I back up & step on & off repeatedly quickly until the vehicle stops. Then do it again several times.

Once the brakes are adjusted correctly the cable doesn't move enough to pull the pawl up until the brakes wear down some.

2 questions: Have you tried partially applying the parking brake then seeing how the brake feels? What method are you using to bleed the brakes?

Q:2 I’ve been using the old pump and open the bleeders starting from farthest point from MC ending on closest point.
Q:1 The parking brake I haven’t tried because I just put new lift kit on installed new cables not sure if it is adjusted correctly yet affraid to push it and then I can’t get it to disengage

 

[DirtDonk]

Can anyone else confirm that about GM power boosters? Cause basically that’s what I have on my bronco.

Nothing really to confirm actually. All vacuum brake boosters act this way.
When they are not activated by vacuum, the pedal is rock hard and so tight that pushing it seemingly does no good. If you’ve ever tried to stop a vehicle with a stalled engine, you have run into this.
If you were to push your foot on the brake before you start the engine, then start the engine while your foot is still pressing the pedal, you would normally feel the pedal drop quite a bit as vacuum assist is introduced into the equation.
The mid 70s Ford passenger cars were probably among the worst for spongy, soft, long travel pedal action.

So it might actually be hard to tell the difference between a spongy pedal from a brake booster versus a slightly spongy pedal from a little air in the system.
You can certainly tell the difference, but it’s hard if you haven’t experienced both.
Maybe a video of your pedal action? I don’t know if that could help us out here, but it’s probably worth a shot.
What are you doing with a GM booster? Is that something in one of the kits? Maybe we’ve been using GM boosters all along and I just wasn’t aware of it? Anything is possible.
Especially since Ford boosters always seem to be in short supply!
Or are we talking about a hydroboost unit here? Guess I better go back and re-read before I put my foot in my mouth any further!

 

[DirtDonk]

Q:1 The parking brake I haven’t tried because I just put new lift kit on installed new cables not sure if it is adjusted correctly yet affraid to push it and then I can’t get it to disengage

Nothing wrong with leaving the parking brakes out of the equation while working on things. But I can’t think of any reason to be afraid they might not release.
If the current drum setup is releasing from hydraulic, there’s no reason for them not to release from mechanical, unless you have them assembled incorrectly.
With no pressure from the connection, what happens when you press the parking brake pedal now? Does it ratchet down normally?
Then when you put your foot behind the pedal and pull the release, does it come up?
If so, then, adjusting them properly, shouldn’t change that.

 

[DirtDonk]

Going back to the first page, does your pedal still go near to the floor?
How far from the floor is it with no pressure on the pedal?
Maybe we can compare your current static height to that of other Broncos. Especially good with factory power brakes to compare to.

As everyone is saying, power boosted brakes often feel softer at the pedal. But actually mushy and super long travel at the pedal, still sounds like air in the system.
Or an improperly adjusted booster rod.
We have talked about that already, haven’t we?

You said all the soft hoses are new? And you’ve been bleeding using the normal method it sounds like, so theoretically everything should be good.
By now I assume you have put a lot of fluid through the system!

 

[El Kabong]

Q:2 I’ve been using the old pump and open the bleeders starting from farthest point from MC ending on closest point.

I'm gonna toss this in here, just to make sure we're on the same page:

2 Man Brake Bleed​

1-Usual safety stuff (Block the wheels, trans in correct gear, on safe axle stands if jacked up, etc.). -Sometimes Broncos are high enough you might be able to do this without jacking it up.​

2-Check the level of the brake fluid, add if needed. Recheck periodically & add as needed throughout the bleeding process. Do not allow it to run out. If it runs out, you must start over.​

3-Have your helper pump the brake pedal a few times & then hold it down. Do not let the pedal up while the bleeder is open.​

4-Open the bleeder valve, observe the fluid flowing from the bleeder. Fluid & air bubbles can spray, it's best to run a clear hose from the bleeder into a container. Some would say wear safety goggles. Keep your mouth closed ;D.​

5-Close the bleeder valve while the pedal is still depressed.​

6-Have the helper pump the brake pedal, observe height of pedal.​

7-Repeat steps 2-6 until no bubbles are seen in the fluid from the bleeder valve, then move to the next wheel, following this order: RR, LR, RF, LF (On newer trucks with the RABS valve, it's RR, LR, RABS valve, RF, LF. On trucks that are newer still with 4 wheel ABS, I don't know). Be sure that each bleeder is closed before moving on. If the brakes are otherwise in good condition, adjusted, & not leaking, the pedal should be firm when done.​

8-Check the level of the brake fluid, add if needed. Recheck again soon to be sure fluid isn't leaking.​