Newly installed aluminum master cylinder spongy brakes

[74bronk]

Ok no more foam in brake fluid. brakes are better (basicly back to where they were with old MC. The brakes work but just not rock hard very spongy just like from Day one of the Wild horses front disc conversion. Starting to wonder if I should just disable the power boost and go manual!

Another issue…..
now the brakes (Front) pull to the right and seems like the left rear want to swing around to the left . Very dis hearting at this point. Any advice or help appreciated

Did you bench bleed the mc again AFTER you tightened and fixed the air leak that was causing the bubbles? You can't skip steps (sorry).

Air in lines will make some individual corners work slightly better and you might experience pulling.

Start from scratch and follow every single step mentioned earlier. We don't know if you have the calipers installed correctly or not. More than a few little things that add up and make it hard to diagnose.

Wish ya the best. I did brakes at a GM dealership 100 yrs ago... every step has to be done right or you will have symptoms. Once you finish it up you will be SO glad you did all the conversion work.

No I didn’t bench bleed it after

 

[nvrstuk]

I really understand the pain here... I think we've all been here but get a fresh start and go through it step by step (again) and unless there's some mechanical issues then hopefully you've got it!

Sounds like you are running stock drums in the rear still?

After you have bled the system and you have "some pedal" after bleeding the system, make sure you adjust the rear shoes properly.

This means that you use the star adjuster with the wheel up off the ground and rotate the wheel until you can hear the brake shoes starting to rub against the drum.
Continue to rotate the star adjuster until you cannot turn the wheel-at all.

Then start to rotate the star adjust the other direction so you are "loosening it" and as you're backing off the star adjuster continue to try to turn the wheel. It will soon rotate some but be dragging on the shoes inside. You WANT this!
You can still hear the shoes rubbing against the drum slightly as it rotates, then you know you have the shoes adjusted properly, repeat for the other side. It's a "I've done this multiple times & I know it's right" feel. For you, spin it by hand and if you can get 2-3 rotations before it stops and the shoes are rubbing when it spins you are good.

This will usually if everything else is done properly will take up that extra long pedal stroke that you might have.

Good luck.

 

[DirtDonk]

Starting to wonder if I should just disable the power boost and go manual! Because with motor not running brakes are very hard and stiff.

That’s how they’re supposed to work. The hard pedal has nothing to do with getting rid of air or sponginess. It means that the booster is not able to assist.
If you disable the booster, you will very likely want to run a smaller master cylinder. So you’ll need a new master cylinder to begin with.
With the typical 1 1/8 inch diameter bore master cylinder that goes along with vacuum boosters, the pedal pressure needed to get the brakes to work is excessive to say the least.
Yes, it’ll work without the booster and it’s been done. But it’s very hard to stop.
You’d want a master cylinder more in the 1 inch or even 7/8 inch size category.
But here you’ll run into a long travel because the GM brake calipers are larger than the Ford calipers. Part of their advantage and disadvantage.

But speaking of going without a booster.… You literally have to get rid of the booster.
You can’t just disable it because then you would have to literally stand on the brake pedal and still might not be able to stop the vehicle safely.
Brake boosters are meant to work with vacuum. Without vacuum, you struggle to get the vehicle stopped in any situation. And that’s any vehicle with any vacuum booster.
So if you are going to run with no booster connected, you would literally have to remove the booster and hook the master cylinder directly to the brake pedal rod.

Another issue…..
now the brakes (Front) pull to the right and seems like the left rear want to swing around to the left . Very dis hearting at this point. Any advice or help appreciated

Any uneven braking coming from the rear is likely shoe adjustment related. Unless one side has become contaminated with oil or brake fluid.
Or could even have mismatched sizes of slave cylinders. Although if it didn’t do this before, and you haven’t changed anything in the rear, then that’s not very likely.
But it won’t be master/Booster related, because they use a common brake line until the rear axle.
Same for the front. Common brake line down to the proportioning valve or H-block, and down to the axle, where it splits off to each side.
Perhaps it’s all coming from the front and the rear just feels like it’s following.

First things first though, and that would be to look over the top of each front tire and verify that you can see plenty of daylight between the caliper and the steering knuckle.
If one side is touching, even only slightly, it will give you uneven braking. And more material will need to be ground off the knuckle.
Other things can cause pull too of course, but that’s at least the first thing to look for.

 

[nvrstuk]

Not trying to be blunt, but if people don't understand what a booster does and what the symptoms are if it doesn't work then because brakes are KINDA important- not just for you but for other innocent people around you - then it should go to a shop so you can be almost gauranteed that they are done right and won't fail causing.... well, causing what brakes do when they won't stop the vehicle.... just saying.

 

[74bronk]

Did you bench bleed the mc again AFTER you tightened and fixed the air leak that was causing the bubbles? You can't skip steps (sorry).

Air in lines will make some individual corners work slightly better and you might experience pulling.

Start from scratch and follow every single step mentioned earlier. We don't know if you have the calipers installed correctly or not. More than a few little things that add up and make it hard to diagnose.

Wish ya the best. I did brakes at a GM dealership 100 yrs ago... every step has to be done right or you will have symptoms. Once you finish it up you will be SO glad you did all the conversion work.

Bench bleed again ”one more time into the breach” will do …..

 

[DirtDonk]

Any luck getting more work time in on it this weekend?
Lots of things can cause a pulling, as mentioned. Were you able to check stuff?
Enquiring minds need to know...

Paul

 

[nvrstuk]

Like Paul mentioned, always nice to get feedback and know you're making progress!

 

[74bronk]

Any luck getting more work time in on it this weekend?
Lots of things can cause a pulling, as mentioned. Were you able to check stuff?
Enquiring minds need to know...

Paul

So I bench bled it reinstalled then bled all 4 wheels then this happens …..the air bubble returned front part of MC only after I fixed this issue before. Plus the brakes are spongey as shit … I bled and I bled still getting foam front compartment of MC any help appreciated at this point

 

[nvrstuk]

MC is bad or you are sucking air past the fittings when bench bleeding it.

 

[gnpenning]

Seems to me some were have trouble with bleeder screws not seating properly and sucking air.

 

[ksagis]

MC is bad or you are sucking air past the fittings when bench bleeding it.

Always wondered in this topic, if a fitting someplace in system is loose enough to suck air in, I would assume it would also leak fluid out at some small rate and provide a clue of which fitting is the problem? Or is it possible a fitting leaks air in but not any fluid out?

Seem to me it’d leak some amount of fluid out, especially at higher pedal pressures.

 

[El Kabong]

Theoretically it's possible to suck air, but not leak fluid, since the fluid is thicker than air. I'd tighten each fitting just a little.

@74bronk What method are you using to bleed the brakes?

 

[74bronk]

Theoretically it's possible to suck air, but not leak fluid, since the fluid is thicker than air. I'd tighten each fitting just a little.

@74bronk What method are you using to bleed the brakes?

I have the fitting very very tight with Teflon tape. The plug on the opposite side is extremely tight with Teflon on it.

 

[Brush Hog]

I’ve always head Teflon tape or any sealer on brake fittings is a no no. Maybe try it without the tape. I could see that causing you to suck air but not leak fluid.

 

[74bronk]

Theoretically it's possible to suck air, but not leak fluid, since the fluid is thicker than air. I'd tighten each fitting just a little.

@74bronk What method are you using to bleed the brakes?

Question is it ok to use thread dope instead of Teflon tape on brake components?

 

[Wild horse 75]

Inverted flare fittings, banjo fittings and brake bleeders do not require any thread sealant of any kind as they don’t seal on the threads.

 

[Speedrdr]

Kind of a sideways hijack here. How do you keep the master from leaking AFTER it’s been bench bled wh n you’re taking out the adapters and hooking up the hard lines? Maybe it’s just put towels under it? Never installed a new master before. Bled lines a bunc, but…

Randy

 

[El Kabong]

I’ve always head Teflon tape or any sealer on brake fittings is a no no. Maybe try it without the tape. I could see that causing you to suck air but not leak fluid.

Inverted flare fittings, banjo fittings and brake bleeders do not require any thread sealant of any kind as they don’t seal on the threads.

x3. No teflon tape on brake fittings. Or on any other flare fittings for that matter. Your problem might actually be caused by the teflon tape.

Most brake line fittings are "Inverted double flare". Look at the top section showing the "Double/SAE 45⁰ inverted flare" in the pic below.

See how the tubing is folded over itself? That's the "Double".

In the cutaway view you can see how the flare fits inside the fitting. That's where the term "Inverted" comes in. (With regular [Household] flare fittings the flare sits over the fitting)

You can see how the flare matches up to a tubing seat in the bottom of the fitting. Where the flare hits that seat is where the sealing happens. The threads are just there to tighten the flare against the seat, not to seal anything.

That's why teflon tape doesn't help. And if a little piece of teflon tape finds its way onto the seat, it can actually cause the flare to not seal.

I never use pipe dope or anything at all on brake fittings. If I lived in the rust belt I might consider super carefully using a sparing amount of never-sieze on the external thread only. But would only be to aid in removal years down the road, not for sealing purposes. The reason for only using it on the external threads would be to prevent anything from being pushed down into the fitting. But here in the land of sunshine I don't use any on brake fittings.

 

[74bronk]

x3. No teflon tape on brake fittings. Or on any other flare fittings for that matter. Your problem might actually be caused by the teflon tape.

Most brake line fittings are "Inverted double flare". Look at the top section showing the "Double/SAE 45⁰ inverted flare" in the pic below.

See how the tubing is folded over itself? That's the "Double".

In the cutaway view you can see how the flare fits inside the fitting. That's where the term "Inverted" comes in. (With regular [Household] flare fittings the flare sits over the fitting)

You can see how the flare matches up to a tubing seat in the bottom of the fitting. Where the flare hits that seat is where the sealing happens. The threads are just there to tighten the flare against the seat, not to seal anything.

That's why teflon tape doesn't help. And if a little piece of teflon tape finds its way onto the seat, it can actually cause the flare to not seal.

I never use pipe dope or anything at all on brake fittings. If I lived in the rust belt I might consider super carefully using a sparing amount of never-sieze on the external thread only. But would only be to aid in removal years down the road, not for sealing purposes. The reason for only using it on the external threads would be to prevent anything from being pushed down into the fitting. But here in the land of sunshine I don't use any on brake fittings.

I’ll go through and remove all Teflon

 

[El Kabong]

I’ll go through and remove all Teflon

Good. That's stuff can be tough to remove. It turns stringy & can be difficult to get all the tiny pieces. A brush can be helpful for getting it out of threads.