I'm at my absolute wits end- Fading Brake pedal despite best efforts

[Azca]

If the pedal isn't hard as a rock, explain how it could be the booster, I just don't see it.

We took vacuum off booster, had hard manual pedal but it faded to no brakes just the same.

It is not about the booster, you are correct, as Beno pointed out it is about the travel distance. Due to the extra distance, if not adjusted, and the resistance of the mechanicals, it will not simply glide until it makes contact. It will "feel" spongy to most people, at least to those of us who aren't experts.

In my case after changing a MC, brakes, all fluids, the brake booster, and bleeding with the two man method, pneumatic bleeding, running a hose from each brake and lpsv to the master cylinder I still had crappy spongy feeling brakes. After replacing the booster I had quite a bit of brake travel and the position of the brake pedal was not too my liking so I climbed back under to adjust. After three complete turns of the adjustment rod I had the best brake sensitivity I have had since I bought it. Nice and firm. No issue with the "travel distance" I have been reading either.

As someone who has to work with personnel who are not electrical experts when troubleshooting electrical issues in electrical distribution systems, it is sometimes difficult to understand what the real issues are, you have to read between the lines. I recently had this when trying to diagnose issues related to power supplies failing at a computer facility. What I am getting at is we all try to describe the problems we are seeing, but if you are not in the business, your descriptions may be misleading. The main culprit for spongy brakes is air somewhere in the system. But when you have ruled that out it must be something else. In my diagnosis of my brake problem I did not understand the ramifications of the push rod not being adjusted, how would I, I am not a professional. I also did not know how it would "feel". A true brake expert probably would have figured this out toot sweet after they also bleed the brakes, or even before if tested.

In the end you pay for experience in one of two ways. You either pay for the professional who has the experience or, you pay for your leaned experience. The later is often times much more expensive...

 

[Dave 2000]

My 80 brakes are brilliant....well alright the handbrake is a bit of a sissy but it passed the inspection. The pedal moves a very small amount before it is applying the brakes, press a little hard and you can feel the brakes coming on strong, once stopped I pressed as hard as I physically could, the pedal is solid.

Unless there is a problem 80's do not have spongy brakes.

regards

Dave

 

[Chester]

It is not about the booster, you are correct, as Beno pointed out it is about the travel distance. Due to the extra distance, if not adjusted, and the resistance of the mechanicals, it will not simply glide until it makes contact. It will "feel" spongy to most people, at least to those of us who aren't experts.

In my case after changing a MC, brakes, all fluids, the brake booster, and bleeding with the two man method, pneumatic bleeding, running a hose from each brake and lpsv to the master cylinder I still had crappy spongy feeling brakes. After replacing the booster I had quite a bit of brake travel and the position of the brake pedal was not too my liking so I climbed back under to adjust. After three complete turns of the adjustment rod I had the best brake sensitivity I have had since I bought it. Nice and firm. No issue with the "travel distance" I have been reading either.

As someone who has to work with personnel who are not electrical experts when troubleshooting electrical issues in electrical distribution systems, it is sometimes difficult to understand what the real issues are, you have to read between the lines. I recently had this when trying to diagnose issues related to power supplies failing at a computer facility. What I am getting at is we all try to describe the problems we are seeing, but if you are not in the business, your descriptions may be misleading. The main culprit for spongy brakes is air somewhere in the system. But when you have ruled that out it must be something else. In my diagnosis of my brake problem I did not understand the ramifications of the push rod not being adjusted, how would I, I am not a professional. I also did not know how it would "feel". A true brake expert probably would have figured this out toot sweet after they also bleed the brakes, or even before if tested.

In the end you pay for experience in one of two ways. You either pay for the professional who has the experience or, you pay for your leaned experience. The later is often times much more expensive...

Not an expert, and on this endeavor, describing the symptoms, however poorly, probably adds to the confusion.

As it was at the beginning, and still is now, spongy all the way to the floor, virtually no brakes. It has felt like a bad master cylinder from the beginning. Where an open line has some resistance to the floor, it has more resistance than that. Maybe the resistance all the way to the floor is like a bleeder valve slightly opened.
Initially, this started suddenly, as if brakes were fine when he parked it, and he had no brakes when he got in the next morning. (some, it could hold him still at idle, but couldn't do more than that)

 

[Chester]

I'm restoring the parking brake now, new rotors and shoes, springs and hardware kit. Over the course of several weeks, the parking brake has been doing a lot of work. This past spring, the linings were fine when we put on new pads, but this has been some torturous duty.

 

[Trux]

I would also check your caliper pistons. The boot seal on the pistons could be ripped allowing air in slowly, thus the slow degradation of braking power over a short period of time.

The fronts could also be stuck in the closed position not pushing on the brake pad - ie no brake power.

 

[musthave]

Update

A few have stated that we're just throwing parts at this rather than finding the true issue.

I've thrown about $1500 of parts at it in fact. But, everything I've bought thusfar are items that needed to be done. Almost like a "while you're in there" thing.

New rotors on all 4, front were OK, had a little life left, but why go through the hassle of taking apart again in a few months, replaced all 4.

New front calipers, we were getting a black substance that looked like rubber on the front right, you replace them in pairs, so both front calipers were replaced.

New pads on all 4, mine probably had a little life left, but again, I'm in there, might as well make them right.

New hoses 6 of 7 done, many people mentioned possible ballooning of hoses, we didn't see any, but a few of the hoses were in need of replacement, easier to get all of them done and know that they are right, and that they aren't the culprit. I still need to aquire a top rear hose and have that replaced that too.

New brake shoes on rear, the right inner / outer axle seals had went bad so there was a bit of a mess. Shoes were pretty shot so they were replaced.

New master cylinder, it only made sense to start here. Tried a NAPA rebuilt one, had the same brake issue so I replaced with new OEM. Oddly, the new one didn't come with the rubber boot/seal that fits into the booster. The original one didn't have it, but the NAPA one did. Odd.

New LSPV, enough people have said that they go bad, my boot had taken a beating, so it made sense to replace it. I'd prefer to keep things the way MR. T designed them, I do agree that it would be a lot easier to delete and use proportioning valves and STILL might do that.

Replacement ABS Actuator, not a new one, but a known working one. Based on the jig that we made up to test the cycling of it and using it both on the newly acquired ABS Actuator, and the one presently installed, we believe that the ABS actuator is good. From what I've heard, they don't really go bad very often. I'd prefer not to delete, but is an option that is still available.


Only thing left is the booster. Is mine good, I don't know. I know that without vacuum to it, I get a incredibly hard pedal, with it connected I get a pedal that is absolutely being assisted by the booster.

Everything is installed, bled the system 5 times around until out of brake fluid, and now have better brakes. Not right yet, but they feel like they're on their way. Driving today and will bleed again this evening to get some more air out after I pick up another gallon of brake fluid.

We are at a point where we can diagnose better with caps and plugs as needed and do so knowing what the issue isn't.

 

[ChiTown]

I have a question and please don't take offense. Which way are the bleeder screws on the front calipers pointing, up or down?

 

[musthave]

I have a question and please don't take offense. Which way are the bleeder screws on the front calipers pointing, up or down?

The screws point up as they should No offense.

 

[izzyandsue]

Found this on the FSM, page BR15 for checking the booster:

BRAKE BOOSTER ASSEMBLY
OPERATION
1. OPERATING CHECK
(a) Depress the brake pedal several times with the engine off
and check that there is no change in the pedal reserve
distance.
(b) Depress the brake pedal and start the engine. If the pedal
goes down slightly, operation is normal.
2. AIR TIGHTNESS CHECK
(a) Start the engine and stop it after 1 or 2 minutes. Depress
the brake pedal several times slowly. If the pedal goes
down furthest the 1st time, but gradually rises after the
2nd or 3rd time, the booster is air tight.
(b) Depress the brake pedal while the engine is running, and
stop the engine with the pedal depressed. If there is no
change in the pedal reserve travel after holding the pedal
for 30 seconds, the booster is air tight.

 

[musthave]

Found this on the FSM, page BR15 for checking the booster:

BRAKE BOOSTER ASSEMBLY
OPERATION
1. OPERATING CHECK
(a) Depress the brake pedal several times with the engine off and check that there is no change in the pedal reserve distance.
(b) Depress the brake pedal and start the engine. If the pedal goes down slightly, operation is normal.
2. AIR TIGHTNESS CHECK
(a) Start the engine and stop it after 1 or 2 minutes. Depress the brake pedal several times slowly. If the pedal goes
down furthest the 1st time, but gradually rises after the 2nd or 3rd time, the booster is air tight.
(b) Depress the brake pedal while the engine is running, and stop the engine with the pedal depressed. If there is no
change in the pedal reserve travel after holding the pedal for 30 seconds, the booster is air tight.

Performed this test again today. Test 1, operation is normal. Test 2 Operation appears normal, the only difference being on part B, after turning off the engine, the pressure pushing up towards me is increased.

 

[Howard705]

That only checks the assist part-diaphragm/valves. You don't need it to bleed or have a hard pedal.
You can cut the vacuum line and drive it if you have a good leg. Unless it's broken inside it won't give you a soft pedal.

 

[fonman]

I offer this for folks on here working with soft pedals and for Musthave when you get it fixed.

You can not really test or 'feel' a soft pedal properly without driving. Engine off and booster bled down, sure. Sitting still in park it just won't feel right even when it is.

 

[DARKNESS]

Unless there is a problem 80's do not have spongy brakes.

Do you have ABS?

 

[Trux]

It sounds like it's your lines detoriorating from the inside. I had the exact same problems on Nissan vehicle - had to have the lines cleared out from allot of rubber particles blocking the parts up.

Ballooning doesn't necessarily mean you'll see them bulge just from the outside. It happens when the pressure is applied ,and it's hard to see. Ballooning IMO means just complete damage or failure of the rubber to provide good back pressure to push against the calipers.

And I'm glad this didn't turn into a 7,978 pager, yet.....

 

[atomicshawn]

Any news? I feel like we're at the end of a mystery novel here.

 

[Pin_Head]

Maybe it is brake zombies: Some problems can never be killed.

 

[Trux]

You have been pushing the pedal to the floor and to get the air out - and THEN closing the bleeder valve while the pedal is still pushed to the floor with a 2x4 or something - correct?

Tried this to each valve etc. bc if you let the brakes up before you close the valve you're getting air in the system every time.

 

[Hornd]

It is not about the booster, you are correct, as Beno pointed out it is about the travel distance. Due to the extra distance, if not adjusted, and the resistance of the mechanicals, it will not simply glide until it makes contact. It will "feel" spongy to most people, at least to those of us who aren't experts.

In my case after changing a MC, brakes, all fluids, the brake booster, and bleeding with the two man method, pneumatic bleeding, running a hose from each brake and lpsv to the master cylinder I still had crappy spongy feeling brakes. After replacing the booster I had quite a bit of brake travel and the position of the brake pedal was not too my liking so I climbed back under to adjust. After three complete turns of the adjustment rod I had the best brake sensitivity I have had since I bought it. Nice and firm. No issue with the "travel distance" I have been reading either.

As someone who has to work with personnel who are not electrical experts when troubleshooting electrical issues in electrical distribution systems, it is sometimes difficult to understand what the real issues are, you have to read between the lines. I recently had this when trying to diagnose issues related to power supplies failing at a computer facility. What I am getting at is we all try to describe the problems we are seeing, but if you are not in the business, your descriptions may be misleading. The main culprit for spongy brakes is air somewhere in the system. But when you have ruled that out it must be something else. In my diagnosis of my brake problem I did not understand the ramifications of the push rod not being adjusted, how would I, I am not a professional. I also did not know how it would "feel". A true brake expert probably would have figured this out toot sweet after they also bleed the brakes, or even before if tested.

In the end you pay for experience in one of two ways. You either pay for the professional who has the experience or, you pay for your leaned experience. The later is often times much more expensive...

This is why I hate it when someone says I just replaced X parts because they have XXXX Miles on them anyhow.
Chasing parts to fix a problem is usually a huge waste of time, labor, and $. I like to know what failed and why.
I can tell you how often I hear "We changed X sensor and that did not fix problem, so it must need a computer."

That's where this site is truly priceless. There are multiple guys that have the same issue, that have already went thru the learning curve.

The Firewall Antifreeze mixing valve is a prime example. You can adjust or you can take it off and try blowing thru it to ensure no passage when closed or your AC blows hot. Leaking Knuckles and Clogged breathers is another example.

Now if someone could only determine why rear door courtesy lights and rear dome lights do not work on several rigs...

 

[NLXTACY]

Any news? I feel like we're at the end of a mystery novel here.

What's wrong with that?

 

[DARKNESS]

Feels more like The Neverending Story