So I have been fighting this low brake pedal issue since I got the car. Basically, the brakes do not start engaging till the pedal is like 2 inches from the floor. Because of the massive brake pedal travel, I can't even lock the wheels by flooring the brake pedal. I took it to a mechanic and just spend $1000 to have the brakes bled and rear e-brake cables changed since they were seized. I have 4 wheel disc brakes and car is an 1988 model. The mechanic can't figure out why there is not brakes and was trying to tell me he thinks it is normal...

This is the second mechanic it has been to. The first changed the master cylinder and a rubber line thinking that was the problem.

I now have like $2500 in trying to fix the brakes and at this point it is not even worth it to take it to a third mechanic, so looking for ideas here.
The e-brake does somewhat work now, it will hold the vehicle from moving at idle in drive, but when pulling it while it driving I can't even feel it and if the car is coasting when I pull it I also can't feel it doing anything.

 

Those rear calipers should be the cast iron Delco Moraine. If so then the pistons need to be rotated out to take up the pad gap. This is normally done by using the parking brake. But with seized cables, this wasn't being done.

There is a tool that is cube shaped with prongs on it to engage the piston and turn it. IIRC, need to remove the caliper from the bracket and remove the pad to access the piston.

RBob.

 

That's about all you will ever get; I've never owned a Thirdgen that will lock-up the rear wheels when the Parking Brake handle is pulled.

If the parking brake handle travels all the way to the top of it travel range than you can adjust the floor cable to take up some of that slack,....... that will allow you to get a bit better 'bite' on the rotors when you pull on the handle. Easiest way to make this adjustment is to remove the driveshaft, get a pair of small vise grips to hold the cable in place, then tighten the adjustment nut ( 13mm IIRC ).

Service manual says,

 

Would using the parking brake every day eventually fix this? Or do I need to adjust the piston manually?

Also, is this the tool https://www.amazon.com/Supercrazy-Brake-Piston-Caliper-SF0134/dp/B00L6I16NK/ref=asc_df_B00L6I16NK/?tag=hyprod-20&linkCode=df0&hvadid=330565141591&hvpos=&hvnetw=g&hvrand=3124354090016965147&hvpone=&hvptwo=&hvqmt=&hvdev=m&hvdvcmdl=&hvlocint=&hvlocphy=9003956&hvtargid=pla-635315236776&psc=1

 

Possibly, could work the parking brakes multiple times just to see if it works/helps.

Appears to be the required tool.

RBob.

 

Sammy, you mentioned awhile back that your engine had came built from the previous owner. Observe your WUD and watch where your kPa is hovering. If it's above 60-kPa in P/N and close to if not over 70-kPa in Gear, it is a low vacuum issue. For the money wasted on those mechanics, you should have reached out and I would have helped you install a hydroboost system for just the cost of the system...

- Rob

 

In a general way, brake booster systems (hydro, vacuum, or otherwise) CANNOT be responsible for "low pedal" type complaints. "Hard pedal", yes; "pedal locks itself after pushing", yes; ANY NUMBER of assist-related complaints, yes; but NOT "low pedal".

Note please, that I am NOT saying "his brake booster is fine", I am NOT saying "hydroboost isn't a good idea", NOT saying "your idea can't help him", NOT NOT NOT NOT NOT NOT NOT NOT NOT NOT NOT NOT. Only, that NO boost system can be responsible for "low pedal". It simply isn't possible for a booster to be the part that allows too much brake fluid to have to move inside the hydraulics before the frictions contact the rotors. Not possible.

I recall when Frod put HB on certain cars back in the 70s. Don't recall the details; but seems to me like that was the VERY FIRST statement in the "troubleshooting" table. "Hydroboost CANNOT cause a low pedal, vibrating pedal, squealing noises, ..." basically a litany of the mechanical or hydraulic problems that a brake system can have.

In this case, d00d has the old Saginaw disc brake system, which is NOTORIOUSLY bad. It just wasn't real well thought through. Even if it worked OK enough when new, or at least well enough to get it past the regulatory bodies, it has aged with less grace than those middle-aged supermodels you see with the trout pout and Joker lips and all that.

Best answer in this case is for the OP to do several things HIMSELF (he MUST leave "shop" out of it):
-

• Buy new (not necessarily "new" new, just, not the old ones that are on the car, unless they're already "new")
• Install the "recall kit" into them
• Adjust them properly, i.e. until they are JUST BARELY off of the rotors
• Install the "Grainger spring" in the proportioning valve, can't recall their part # off the top of my head but a brief search of this forum for "Grainger" and "spring" should turn it up
• If the pedal is STILL low, bench-bleed the master cylinder
• Use the parking brake EVERY SINGLE TIME WITHOUT EXCEPTION that he steps out of the car, and twice on Sundays, just for good measure; John's scan of the FSM page gives a pretty strong hint in that direction, no??

That said, I have HB in my truck. I LOVE it. It is SO MUCH BETTER than vacuum boost it's not even fair. It would make a great upgrade.

But it makes no sense to attempt an "upgrade" to a subsystem that's fundamentally BROKEN in some other way besides what the "upgrade" addresses.

 

Well... I don't want to turn this thread into an argument, it serves no purpose. And, it's not that I don't agree with the above, but I'm pretty sure it is a low vacuum issue. Just need him to confirm his kPa on his WUD screen at idle. Realistically, after spending $2500.00 on two different shops, the assumption here is that every conceivable part in the braking system has been gone through. However, I doubt they scanned his engine data, nor even hooked up a vacuum gauge to see the Hg for that matter. But to the point, spending $2500.00 on an inferior braking system from the 80's for it not to work was an absolute waste of money, and an upgrade for $800.00 would have suited him very well. For that kind of money the guy could have gone LS1, to put things into perspective...

- Rob

 

Vacuum does not cause a low pedal.

 

Grainger spring part numbers are here,

https://www.thirdgen.org/forums/brak...ng-torque.html

​​​

 

Sigh...

During highway speeds or off idle from stop light to stop light...?

Followed by...

.

New master cylinder installed by first mechanic, followed by brake bleeding all around from the second with the addition of new e-brake cables. Let's assume that the brake shop knows what they are doing and that fluid was actually coming out when the pedal was being depressed during the process...

What is the intent here for pulling the e-brake while driving? Are you trying to drift? A hard pedal from low engine vacuum comes after the initial attempt at trying to stop during a low speed. You will be moving say 5-mph, hit the brake, but the brake goes to the floor barely catching, so you lift and hit the brake again (pumping) out of desperation but now you notice the brakes feel hard and locked out. This is more than likely due to a large camshaft especially when the mechanic himself claimed it must be normal because he found no issue when manually checking the brake system with the proper equipment...

Edit: This is also why there is a market for vacuum canisters.

- Rob

 

So the low/soft brake pedal happens at all driving conditions and feels the same were brakes do not begin to engage the rotors until pedal almost touches the floor. The kPA in park is around 55 I believe. Fluid does come out the bleeders when pressing the pedal right away. I was only pulling the ebrake while coasting below 5 mph to see if was engaging the rear calipers properly. Regarding the cam, it's very mild in my opinion. It doesn't have much lope to it like I have seen on sbc's that I have owned.

I did call the mechanic who worked on the brake cables, and he said they tend to stretch an inch or two and need readjustment to work properly. This seems to be the case because I noticed when I picked the car up I could barely pull the ebrake up, but now the ebrake has pretty much full travel. Will be tightening up the cable after the holidays to see if helps and update the thread. If that doesn't work I'll try the square tool thing and see if that works.

Is there a way to test the master cylinder to see if it needs bench bleeding without taking it off the car? The car did blow a brake line in the front after it was replaced and the resivoir for the front brakes did run dry. It was bled by me to regain function of the brakes and later bled again by the second mechanic. I would like to note that the low brake feeling existed before the brake line started leaking.

 

Good deal. For that kind of money with no positive results, let the freaking mechanic get back on it.

Okay, this is what I was talking about. 55-kPa is about 13" of vacuum at idle. When you go into Gear, expect to drop about another 2" of vacuum, so expect to be close to 11" to 10" of vacuum when you're in Drive. It's the overlap that might be your issue. Now will a vacuum canister fix your issue? I have no idea. But... it is something to remember to tell the mechanic when you get there okay....

Best of luck with it...

- Rob

 

Low vacuum CANNOT cause a low pedal. CANNOT.

Note again, I am not saying, "his idle vacuum is fine", "he has enough vacuum", "he won't benefit from improving the vacuum or the system", etc. etc. etc. NOT. NOT. NOT. NOT. NOT. NOT.

Only, that the cause of a low pedal, CANNOT be low vacuum.

His problem is in the HYDRAULIC or MECHANICAL parts of the brake system. HAS TO BE. There is no other thing that can cause a low pedal. Either there is too much space between the frictions and the steels, requiring too much fluid to be moved into them before they contact; or, there's air in the system, of which the most likely place is in the MC from not being properly bled on the bench before installation, which is NECESSARY in these cars because there is SO MUCH cylinder that ends up ABOVE the line fitting and therefore traps air in there that CANNOT be removed by normal gravity or pressure bleeding; or the MC itself is defective; or there's some other mechanical problem.

But the cause of his "low pedal" CANNOT be related to vacuum.

Telling some "mechanic" that has ALREADY PORKED THE POOCH on this job stuff like that will only confuse the issue further and cost him more money without fixing the car.

He CERTAINLY has enough vacuum at times other than idling, such as when coasting at cruising type speeds with the car dragging the engine, that if vacuum was his ONLY problem, he would have a normal pedal AT LEAST SOME of the time. Vacuum CANNOT be the cause of his low pedal.

Mr./Ms. msammy93 HIM/HERSELF needs to do this work to this car, and leave "shop" and "mechanic" out of it, since unfortunately they're obviously incapable of doing anything useful beyond merely emptying msammy's wallet.

 

Sofa is correct. Vacuum assist is just what the words sound like: a pedal effort assist. It does not change the relationship between pedal travel and braking system pressure. It only changes foot effort to make the pedal travel. If you lost all vacuum assist then the pedal would be really hard to push but you'd still get the same braking if you could manage to push the pedal through it's travel.

A low pedal means part of the pedal movement is being wasted on something that's not making pads build pressure on the rotor.

Ideally, foot moves pedal --> pedal moves a piston --> piston moves fluid --> fluid moves caliper pistons --> pressure skyrockets in hydraulics after all the hard parts come in contact --> more hydraulic pressure, more braking force. The only reason there is any pedal travel at all after the pad meets rotor is because parts aren't totally rigid and flex under pressure.

So a low pedal (wasted movement) could be,

* too much gap between hard parts before they come together.
* weak parts that flex too much under pressure.
* air in the system that compresses.
* a slow leak.

 

Ouch!

Owning an old car and paying somebody else for work is a tough position to stay in. I put 100X more time in my old Firebird to keep it running than all my other cars combined. Speaking for myself, there is no way I could afford to have the Firebird if I didn't work on it myself.

 

I'm not familiar with thirdgen rear calipers, but if they are the eldorado style with the lever- if you can live without the e brake change out to late 9o's d52 s10 front calipers, world of difference. My 2015 Honda has this pos design- guess what, both seized on a mt car even when the ebrake is used daily.

 

Is there a way to check if the issue is with the master cylinder while it's on the car?

 

So I checked it today and it actually 48 kPA at idle 825 rpm. Btw, what's kPA does a stock engine have? Just wondering as I thought my engine sounds very mild at idle. Supposedly it's a "nitrous can" whatever that means lmao

 

Hey, 48-kPa isn't that bad, but I would still make a point of telling the mechanic so he is aware. Mechanics nowadays rarely venture into anything unrelated than what they are paid to do, using an analogy from my field, it's kinda like not being able to talk investments with a customer without being licensed, despite knowing about them. Stock engines should have close to, if not over 20" of vacuum at idle because it runs a broom stick of a cam, roughly 30-35-kPa. Yours may sound very mild, but a good exhaust will conceal overlap to the unknowing, but a gear head will hear it right away through the exhaust, regardless. The most recent video of my engine before I pulled it sounded very mild at idle too, and very smooth thanks to the exhaust, yet the kPa was close to 60-kPa in P/N (12.5" of vacuum). and close to 70-kPa in gear (10" of vacuum). I had the same exact issue as you, no brakes whatsoever after the first pump, was impossible to drive in bumper to bumper traffic without a vacuum canister for fear of hitting into someone, and would definitely not trust it on the highway at those speeds pre-canister. The canister helped, but hydro-boost is better. Doesn't mean the stock brake system won't work, but after spending $2500.00 for the stock brake system to work normally, it better sing and dance for you... which is why I suggested hydo-boost.

- Rob

 

Not really...

It has to be held level while bleeding it. I don't think it's possible to do that with it in the car. I don't even think you can unbolt it and warp it any kind of way, far enough to get it level.

"Bleeding" relies on any air in the system rising to the highest point inside the various things the fluid is in, allowing it to be pushed down the lines to the calipers, where the bleeder screws are at the very top of the fluid chamber, and it can escape. The MC however, has 2 cylinders (one for front brakes, one for rear) which are each around an inch dia and 2" long; but the lines go into the side of them at the middle. If the cyl is held level, then the line fittings are at the top; but when the cyl is tilted the way it is when installed in these cars, the half of each cyl that's in front of the lines, is ABOVE the line fitting for that cyl. The air that's in there CANNOT be bled out in that position. Doesn't matter if you "gravity bleed" it (what most of us do in our driveway), "pressure bleed" it (using compressed air to force fluid down the lines from above), "vacuum bleed" it (using suction at the calipers to "suck" fluid down through the lines), or WHAT. You can run a gallon of fluid through it every single day from now to Doomsday using ANY or ALL bleeding methods of your choice, and 2 gallons every Sunday just for good measure, and that air will STILL be right there. I should note that our cars are somewhat unique in this way: in most vehicles, the MC is MUCH more nearly level than in ours when in its normal home.

Only solution is to remove it, clamp it in a vise or otherwise hold it still, put little "bleeder hoses" on it (like they give you when you buy a MC at the parts store) that allow the fluid that the cyl expels when you operate it, to return to the reservoir, while their ends are submerged in the reservoir fluid to prevent air from entering them from that direction. Then the cyl can be installed, and it will be free of trapped air. I strongly suspect that this is the reason, or at least part of it, for your brake system's failure. If I had just bought a car and it had this behavior, it's the first thing I would do. Next thing would be to go through the rear caliper list I gave you, because those calipers are well and widely known to be a total POS, but those things that I told you about will DRAMATICALLY improve their performance, to the point they may even almost be the equal of drums.

Messing with the power assist however, in ANY manner way shape form or fashion including even THINKING about intake manifold kPa, is GUARANTEED to accomplish EXACTLY NOTHING toward fixing a "low pedal" complaint. It is NOT the cause of the problem you're trying to fix. It would be logically the same as, if your car wouldn't start, buying it new tires. It may well be that it needs new tires; it might be undriveable with the ones that are on it; the new tires might be 100 times better in every way than the old tires; new tires might be A Good Idea IN EVERY WAY; but the engine STILL WON'T START. Tires won't fix a no-start no matter how much of A Good Idea they might be. In the same way, messing with the power assist WILL NOT FIX a low pedal, no matter what. It's simply the wrong thing to work on, given the goal at hand to be achieved.

 

Is there any possibility the pushrod between the vacuum booster and the master cylinder is too short causing the delay in braking??? I know I have had to adjust the pushrod once when I replaced a master cylinder, I replaced it twice with the same recurring issue, then I checked and the pushrod was too long in my case causing the brakes to drag. Everything was stock and parts were new and they didn't play nice together in my situation, so Im throwing it out there to check the pushrod and make sure there is no slack in between since most people just bolt them together assuming that all is well, as it very well should be, but I would double check since its easy to do.

 

Sammy, I’m in West Windsor NJ, did you solve your brake issue?

I’m no expert or mechanic, just owned my car since 1987. Becoming active here since I want to start working on mine (yet again). And met StreetLethal here a couple weeks ago, he isn’t far from us either, but would listen to them before me.

As the others have mentioned, the rear calipers are not very good on our cars, I struggle with mine all the time. I had to replace both rear calipers a while back, and my brakes were decent for a while. I believe they need to be adjusted, and don’t believe any mechanics actually know how to do so. At least the few that I have encountered. I’m planning to check a few things; take the calipers off, check that the pin on the back of the pad is actually in place of the caliper piston, adjust the calipers emergency brake arm position making sure it engages with minimal movement (1/8 or 1/4 iirc).

Basically will follow this video:
Let me know if ya want to catch up, since we are very close to one another...