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Old 11-05-2021, 07:06 AM   #1
ZepSL2
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Default Brake problem

So car has been sitting for a week I hop in start it up brake peddle goes to the floor. Service light comes on. I pump the brakes a few times nothing, still to the floor, still no resistance. I figure i had a leak and it was so i get out (car still running) pop hood look in brake fluid reservoir and it is full. Hmmm........ Just to be sure I then look at each wheel and see no brake fluid. Hop back in car shut it down.

Now i pump the brakes to see if I can get them firm. A few pumps and ROCK SOLID and right at the beginning/top of peddle movement. I hold the brake for over a minute to see if there is a slow leak and ZERO movement.
I start car back up and brakes are back and no service light!

WTF???? (scary to drive a car with brakes that can just go out)


I decided to drive around the block a few times and the brakes are working now but a bit spongy though. The more i drove the less spongy they got

1999 SL2 with ABS (63K miles)


Thoughts?
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Old 11-05-2021, 08:03 AM   #2
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Default Re: Brake problem

pump them up with the car off until they are solid and then while holding the brake down start the car.

Petal should drop 1" to 1 1/2". Any more than that and the booster is bad.

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Old 11-05-2021, 12:06 PM   #3
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Default Re: Brake problem

The brake booster may be bad, but that test above isn't going to find this particular variety of "bad".

The pedal pushes on a rod, that pushes on the booster, that then pushes on the master cylinder. For the brake to go suddenly back-and-forth from good to bad (and back to good), there must be a mechanical piece in that "push" train that is disconnecting. My best guess is the pivot at the pedal arm to first push rod is broken in some fashion.

go to the photos below and scroll down to the cut-away diagram on the second page, to see what is inside a typical pedal/booster/master arrangement

https://images.search.yahoo.com/sear...g&action=click
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Old 11-05-2021, 02:01 PM   #4
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Default Re: Brake problem

Only 63k miles on this '99 SL2? A garage queen rarely driven?

When were brakes serviced, including replacing brake fluid. New DOT-3 brake fluid is almost clear with a light honey color. Since it absorbs moisture in the air (the master cylinder cap is vented), fluid eventually turns dark, lowering its boiling point. While not written in stone, once brake disc pads are replaced, pushing caliper pistons back to home position, replacing brake fluid with bleeding is recommended (all for wheels). About a pint of fluid is used in brake flushing/bleeding procedures so a quart is the minimum needed.

When pumping the brake pedal with engine off, the vacuum power brake boost unit is exhausted of reserve vacuum hence the initial pedal application is soft as power assisted braking uses this reserve vacuum. Subsequent pedal pumps should result in exhausting the vacuum reserve as the pedal travels less until al vacuum is depleted. This is the point when only the brake master cylinder is creating hydraulic pressure on brakes without power assist from the depleted vacuum boost unit. You're feeling only the hydraulic pressure feedback from the master cylinder. This is considered normal.

When the engine runs, vacuum is supplied to the brake vacuum boost unit. Applying brakes automatically couples power assisted braking with hydraulic pressure. Under most conditions, the pedal will sink to about half way and feel semi soft - power brake units multiply forces on the master cylinder to provide neck snapping emergency stops regardless whether or not abs is activated. When your brake pedal went to the floor with engine running zero leaks anywhere, this points to a master cylinder problem. Something like 800-1200 psi is generated in brake systems. Despite being assured of the brake pedal not going to the floor while pumping the pedal with the engine off, the power assisted vacuum boost unit still applied pressure in proportion to pedal effort to overcome the master cylinder going to the floor. This will repeat as long as nothing is done and as erratic as it appears with no rhyme or reason.

Understanding the difference between reliable time tested hydraulic brake systems and vacuum power brake assist units can help determine where fault lies. Even if the brake system is gone over and replacing brake fluid, this problem may remain as the heart of hydraulic brake systems is the brake master cylinder generating hydraulic pressure, not the power brake unit. Worse case scenario of a dead abs and dead power brake unit is the default hydraulic brake system that will bring a vehicle to a stop. It will take a huge effort to stand on the brake pedal when power assisted braking fails. . The pedal going to the floor is not a power brake unit issue. A worn master cylinder is. Personal experience with the same symptoms from 40 yrs ago before abs.
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Old 11-06-2021, 05:44 AM   #5
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Default Re: Brake problem

Quote:
Originally Posted by Highmile View Post
pump them up with the car off until they are solid and then while holding the brake down start the car.

Petal should drop 1" to 1 1/2". Any more than that and the booster is bad.

Highmile
'95 SL1 742k and counting
just did this (5 am here in Philly) and it only dropped an inch WHEN IT IS WORKING. When it is not working to the floor. After it runs for 5 minutes it is almost to normal. I even can short stop with the best of them.


It is when i first turn engine on that it is not working



Oh and another thing before i started the car up i pushed the brakes and it was ROCK SOLID still from 24 hours ago when i 3 pumped the brakes and did the hold test. So no vacuum leak in booster.

I also idled for a few minutes pushed brake to floor and shut engine off and brake pedal stayed down. It didn't start to rise so i think the check valve is good.
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Old 11-06-2021, 05:46 AM   #6
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Default Re: Brake problem

Quote:
Originally Posted by billr View Post
The brake booster may be bad, but that test above isn't going to find this particular variety of "bad".

The pedal pushes on a rod, that pushes on the booster, that then pushes on the master cylinder. For the brake to go suddenly back-and-forth from good to bad (and back to good), there must be a mechanical piece in that "push" train that is disconnecting. My best guess is the pivot at the pedal arm to first push rod is broken in some fashion.

go to the photos below and scroll down to the cut-away diagram on the second page, to see what is inside a typical pedal/booster/master arrangement

https://images.search.yahoo.com/sear...g&action=click
not much to it but no way for me to tell if a rod etc is broken and with engine off it works fine. I mean i can put huge pressure on the peddle and there is no strange sounds or unexpected movement
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Old 11-06-2021, 06:16 AM   #7
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Default Re: Brake problem

Quote:
Originally Posted by fdryer View Post
Only 63k miles on this '99 SL2? A garage queen rarely driven?
yes and I forgot to mention new master cylinder put on 3 years ago. That is why i did the engine off 3 pump push and hold. When my old MC went out If i held the brake down hard for a minute or more it would slowly go to the floor. turned out fluid was blowing by the MC seals.


Quote:
Originally Posted by fdryer View Post
When were brakes serviced, including replacing brake fluid. New DOT-3 brake fluid is almost clear with a light honey color. Since it absorbs moisture in the air (the master cylinder cap is vented), fluid eventually turns dark, lowering its boiling point. While not written in stone, once brake disc pads are replaced, pushing caliper pistons back to home position, replacing brake fluid with bleeding is recommended (all for wheels). About a pint of fluid is used in brake flushing/bleeding procedures so a quart is the minimum needed.
full service was 3 years ago when MC was replaced. front calipers are brand new. rear drums are originals. I checked again for leaks today and found none.



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Originally Posted by fdryer View Post
When pumping the brake pedal with engine off, the vacuum power brake boost unit is exhausted of reserve vacuum hence the initial pedal application is soft as power assisted braking uses this reserve vacuum. Subsequent pedal pumps should result in exhausting the vacuum reserve as the pedal travels less until al vacuum is depleted. This is the point when only the brake master cylinder is creating hydraulic pressure on brakes without power assist from the depleted vacuum boost unit. You're feeling only the hydraulic pressure feedback from the master cylinder. This is considered normal.
yes and why i did the engine off 3 pump rock solid pedal and hold test. Going by that the MC is fine and there are no major leaks.



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Originally Posted by fdryer View Post
When the engine runs, vacuum is supplied to the brake vacuum boost unit. Applying brakes automatically couples power assisted braking with hydraulic pressure. Under most conditions, the pedal will sink to about half way and feel semi soft - power brake units multiply forces on the master cylinder to provide neck snapping emergency stops regardless whether or not abs is activated. When your brake pedal went to the floor with engine running zero leaks anywhere, this points to a master cylinder problem. Something like 800-1200 psi is generated in brake systems. Despite being assured of the brake pedal not going to the floor while pumping the pedal with the engine off, the power assisted vacuum boost unit still applied pressure in proportion to pedal effort to overcome the master cylinder going to the floor. This will repeat as long as nothing is done and as erratic as it appears with no rhyme or reason.
hmmm... since it was a new OEM MC put in 3 years ago that is all i can say is hmmm.... lol



Quote:
Originally Posted by fdryer View Post
Worse case scenario of a dead abs and dead power brake unit is the default hydraulic brake system that will bring a vehicle to a stop. It will take a huge effort to stand on the brake pedal when power assisted braking fails. . The pedal going to the floor is not a power brake unit issue. A worn master cylinder is. Personal experience with the same symptoms from 40 yrs ago before abs.
I think you are on to something and I'll tell you why since i did the test just 30 minutes ago. Takes no effort to brake when it is working so IMHO booster is fine/power assist is not the issue. Because of the engine off test 3 pump hold and it was rock solid for over a minute i decided to take the car for a spin and slam the brakes on a wet street and the Brakes locked up

the ABS NEVER CAME ON. I checked the fuse it was good. I now think the ABS pump is dead??? What is strange is as i drive the car the pedal gets closer and closer to normal. If ABS was issue could that cause this behavior? When you first start car up what does ABS system/pump do? Could it some how remove fluid out of the system then driving for a few minutes is why it goes back to normal as everything stabilizes?

thoughts?
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Old 11-06-2021, 09:10 AM   #8
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Default Re: Brake problem

1- the vacuum brake boost unit uses a check valve for one reason; vacuum from the intake manifold occurs only when the engine's running. When the engine is off, tis check valve prevents the vacuum reserve in the brake boost unit from letting in atmospheric air into the brake boost unit. When you pump the brake pedal with engine off, you're metering vacuum on each pedal press for power assisted braking. The vacuum reserve is only good for a few pedal presses until the vacuum is used you hence the pedal becoming firmer on subsequent pedal presses until the brake boost is lost and you're feeling 100% hydraulic pressure.

If the check valve fails, you'd lose power brakes as soon as the engine stops. You won't feel anything while driving and braking. The check valve is to retain vacuum in the boost unit once the engine is off as in a sudden dead engine while driving yet you'll still have power assisted braking for several pedal applications, enough to bring the car to a stop.

2- unless you're familiar on how to disable power brakes, disabling the vacuum line to the brake boost unit and plugging the vacuum line, you cannot test the brake boost unit. If you manage to disable the vacuum line to the brake booster unit then you'd have only the basic brake system. Be extremely aware that you may not have leg strength to stop a moving car at speed without power assisted braking. If you disable vacuum to the brake boost unit, you assume all risks to injury to yourself, your car and anyone/anything you come into physical contact with if you don't anticipate a worse case scenario of zero power assisted braking.

I drove a 2-seat Fiat 850 Spyder with plain hydraulic brakes. No power brakes. The car weighed less than 2k lbs and can lock up its brakes on 13 inch narrow tires easily. It didn't need power brakes because the car was very light. Try stopping a car weighing 3k lbs without power brakes. If you do, do it in a secluded parking lot or seldom used road away from traffic. You don't want to find out the hard way when power brakes are lost or deliberately disabled and rely only on the basic hydraulic brake system.

Once a master cylinder is replaced and past its warranty, no one will tell you its going to work forever. You already replaced the original mc and now on your second one. Since there's no guarantee that your replacement will last as long as the original.......... don't assume it's fine. And you haven't mentioned whether or not a full brake fluid replacement was performed when the mc was replaced. Hydraulic brake systems are not diy friendly by any stretch of the imagination. Unless you're familiar with how hydraulic pressure is created to distribute pressure to all four wheels, periodic fluid replacement and ensuring your diy repairs are similar to brake shops liable for any mistakes from taking short cuts or performing less than professional repairs, you assume all risks for diy mistakes. While it's not rocket science, hydraulic systems are not discussed in detail due to misinformation and misleading suggestions on troubleshooting brake systems. Add abs into this and more misinformation is spread.

Abs is invisible to the hydraulic brake system until a panic stop occurs when a driver feels the immediate foot massage - once abs activates, this allows steering away from a crash but may likely end up crashing into something anyway. The ones activating abs, most likely from tailgating at speed and not rear ending the vehicle in front learn not to tailgate. Inadvertent abs activation whether intentional or not can be a learning experience. If your car never activates abs when you jam the brake pedal and you can hear the brakes lock up from the squealing tires then you have another problem that may or may not be related to the brake pedal going to the floor.

In everyday brake repairs, all brake repairs are performed with engine off. This means abs cannot operate and shouldn't interfere with brake fluid replacement. Fluid flushing and bleeding is the same whether or not abs is part of the brake system. Since abs is off, all abs valves are closed to the brake hydraulics, making fluid replacement a no-brainer. In theory and in virtually every brake repair, abs remains invisible to the brake system whether in repairs or driving. Once emergency/panic braking occurs and abs activates, the motor pressurizes the system, blocks off driver braking input, and performs high speed calculations on which wheel is locking up to release brake pressure then reapply pressure, cycling hundreds of times per second, comparing the fastest wheel speed to the slowest/stopped wheel. The foot massage is the feedback from motorized hydraulic pressure and valves opening and closing as abs is performing all the braking instead of the driver that's now along for the ride. If an accident is avoided and brake pedal released, abs shuts down and returns to standby condition awaiting another panic stop.

If for unknown reasons a brake repair was performed with engine running, fluid was replaced, and somehow abs was activated, these three conditions can contribute to allowing air into the abs system that may result in unusual brake problems. Abs is never flushed or bled and requires GMs scantool and trained technician to perform abs bleeding procedures. Since virtually every vehicle with abs doesn't need abs servicing, abs is left alone otherwise introducing problems can occur from incorrect assumptions or procedures.

In our Saturns and from service manuals, turning the ignition switch on sends power everywhere. The instrument panel gauges and indicators all turn on as part of the lamp test. The pcm performs its own power up self tests. The airbag and abs modules performs their own power up self tests at this time. These modules turn on their indicators in the i/p cluster then turn off if their self tests pass. However, abs has one more step in its self tests, waiting for the driver to drive. On the initial drive off, the abs unit detects wheel speeds and some may hear a zinging sound from the engine. This is the abs motor turning on then off and possibly exercising all the solenoid valves. All occurring under 15 mph on the first drive after each and every startup. If all goes well, the abs indicator remains off. The abs indicator is the only tell tale informing the driver of abs status. If for any reason the abs indicator turns on and remains on, abs detected an internal error and disables itself from interfering with everyday braking. On some models, if the abs indicator flashes during panic stopping, this tell tale along with the foot massage is alerting the driver of abs activation.
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Old 11-06-2021, 01:17 PM   #9
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Default Re: Brake problem

Oops, you stated at the beginning that this has ABS, but I overlooked that. ABS turns a fairly simple and reliable braking system into one with many new possible problems! I may not be able to help here.

The symptom that (I think) you are describing, a complete loss of all pedal resistance and then mysterious recovery, does not relate to a MC problem or a booster vacuum system problem; I urge you to not waste any more time wondering about those. However, the booster may not always be "passing through" the push to the MC, so the booster may have to come off for visual inspection.

Did you inspect the brake pedal arm and push-rod at all? Just a simple peek at it may be all it takes...
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Old 11-07-2021, 08:07 AM   #10
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Default Re: Brake problem

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Originally Posted by fdryer View Post
However, abs has one more step in its self tests, waiting for the driver to drive. On the initial drive off, the abs unit detects wheel speeds and some may hear a zinging sound from the engine. This is the abs motor turning on then off and possibly exercising all the solenoid valves. All occurring under 15 mph on the first drive after each and every startup. If all goes well, the abs indicator remains off.
well there is a noise that kicks in about oh 5 to 10 seconds after i start driving I always wondered what that sound was maybe it is the ABS, It sounds more like ummmm..... geez not zinging more like a fluttering sound (SUPER LOUD) and it last a few seconds and it only does it that one time until car is shut off and restarted then it does it 1 time again etc... like you said above.

Quote:
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The abs indicator is the only tell tale informing the driver of abs status. If for any reason the abs indicator turns on and remains on, abs detected an internal error and disables itself from interfering with everyday braking. On some models, if the abs indicator flashes during panic stopping, this tell tale along with the foot massage is alerting the driver of abs activation.
[/QUOTE]

well I see the ABS light come on for a few seconds at startup then it goes out so it must be passing the first few tests. Then as I pull away it does what I described above.

Yeah ABS did not engage and wheels locked I slid on wet road about 20 feet. I would have done it on gravel but no idea where near me is a gravel or dirt road lol

My other Saturn the ABS never made that strange sound and it worked great. Got the pulsating pedal if i say braked hard in snow etc...

What happens if i pull the ABS fuse? I assume I get the ABS dash light and it stays on forever but can it be driven or/and tested?
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Old 11-07-2021, 08:13 AM   #11
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Default Re: Brake problem

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Originally Posted by billr View Post

However, the booster may not always be "passing through" the push to the MC, so the booster may have to come off for visual inspection.

Did you inspect the brake pedal arm and push-rod at all? Just a simple peek at it may be all it takes...
interesting


no i did not it was 5am both days and pitch dark out and 30 degrees Ill have to dig out a flash light and give it a look see. (I'm night shift so I sleep during day light like a vampire)
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Old 11-07-2021, 10:17 AM   #12
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Default Re: Brake problem

Pulling the ABS fuse means the ABS light stays on and the brakes work properly.

ABS does a noisy self test (louder in 1st gens, probably quieter in 3rd) as soon as the car first hits 5mph, forward or reverse, and if you need to brake at that time...may GM help your soul 'cause the brakes wont do a darned thing until it's over.
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Old 11-07-2021, 10:39 AM   #13
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Default Re: Brake problem

ZepSL2, owning or driving a few vehicles and recognizing when abs performs its self tests on the first drive of the day helps when trying to compare abs braking. You're fortunate enough to have two cars with abs and noticing one locks up brakes (indicating abs failure) while the other car does the foot massage when abs activates.

It doesn't matter if the 'test' surface is a wet road, gravel, dirt, large parking lot or private driveway to test abs braking as long as it's performed safely without distractions (traffic, people, obstacles, etc). I use a snow covered street to test abs and tire traction as tires wear down. Rainy days allows learning about tire traction and abs too when performed in a safe manner, under 30 mph away from traffic. There's always the hard way of learning tire traction limits and abs when an expensive crash occurs........

The abs light is part of abs wiring to turn on the abs light. If the abs fuse(s) are pulled then the unpowered abs circuit can't turn on its abs light. Pulling abs fuses will disable abs operation. Whether or not the abs light turns on is anyone's guess. You've already proven abs didn't activate by feeling and hearing brakes locking up, tires squealed and car skid. The question is why abs didn't activate and why the abs light didn't turn on long before you found out abs wasn't working. Your descriptions of unusual abs behavior is very strange. When abs fails, it's supposed to turn on the abs light to inform the driver that abs isn't available. Brakes still work as they were designed.

You can pull abs fuses as this does not kill the brake system. The basic hydraulic brake system remains as designed since it was invented - hydraulic pressure to operate four wheel brakes regardless whether or not abs is functional or dead. Remember, you are deliberately disabling abs and rely on brakes before abs was invented. You assume all personal risks in testing, troubleshooting and determining why abs failed in addition to the brake pedal going to the floor. Perform braking tests carefully and never assume brakes work since you already know the pedal goes to the floor. Brakes are compromised (worse case scenario) with no guarantee they work in everyday driving. As a diyer, you assume these risks. Brake repair shops or GM are your other options if you feel this is beyond you. The vacuum powered brake boost unit isn't the problem, leaving the abs and hydraulic brake system to diagnose.

It's well known long before the invention of abs for every vehicle's ability to lock up brakes. Abs simply prevents brakes from locking up while allowing drivers to steer away from an impending crash. The vibrating brake pedal is the tell tale along with a flashing abs indicator.

Last edited by fdryer; 11-07-2021 at 10:46 AM.
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Old 11-07-2021, 03:46 PM   #14
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Default Re: Brake problem

Btw, whoever replaced the master cylinder would leave the brake pedal/brake boost push rod as is to eliminate adjusting the push rods. This presumes a straight replacement of one mc with a direct replacement mc so rod adjustment isn't needed. This maintains alignment when brake boost is needed. Is this what occurred or did someone adjust this rod?

Whether you're aware of this or not, power assisted brakes vary the amount of power braking in direct proportion to brake pedal travel. Little brake pedal travel, little power assist. More brake pedal travel, more power assist up to maximum assist without blowing master cylinder seals. With my limited knowledge, I've never read of anyone misadjusting the rod (perhaps shortened) to increase when power assist comes on). Lengthening the rod implies delaying assist. It's possible although unlikely for anyone to misadjust this rod and have more power assist, overcoming the master cylinder, effectively allowing power assist to push past the design limits of new master cylinder piston seals. This would suggest incorrect rod adjustment and damaging the mc piston seals.

It wouldn't be surprising for this mc to fail. This is in addition to a problem with abs.
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Old 11-09-2021, 03:17 AM   #15
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Default Re: Brake problem

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Originally Posted by fetchitfido View Post
Pulling the ABS fuse means the ABS light stays on and the brakes work properly.

ABS does a noisy self test (louder in 1st gens, probably quieter in 3rd) as soon as the car first hits 5mph, forward or reverse, and if you need to brake at that time...may GM help your soul 'cause the brakes wont do a darned thing until it's over.
ahhh yeah my other car was 2002 this one is 1999 and the noise is LOUD.

I'll try with fuse pulled and let everyone know what happened.

really? no brakes during that ? geez what kind of design is that!
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Old 11-09-2021, 03:28 AM   #16
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Default Re: Brake problem

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Originally Posted by fdryer View Post
It doesn't matter if the 'test' surface is a wet road, gravel, dirt, large parking lot or private driveway to test abs braking as long as it's performed safely without distractions (traffic, people, obstacles, etc).
yes i know but that was about MY TIRES i do not like flat spots


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Your descriptions of unusual abs behavior is very strange. When abs fails, it's supposed to turn on the abs light to inform the driver that abs isn't available. Brakes still work as they were designed.
well the MC was replaced so who knows what happened with ABS. Maybe they messed it up some how or let air get into it? i do not remember ever needed ABS since then so didn't know ABS was not working. Bad system GM made here.


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You can pull abs fuses as this does not kill the brake system. The basic hydraulic brake system remains as designed since it was invented - hydraulic pressure to operate four wheel brakes regardless whether or not abs is functional or dead. Remember, you are deliberately disabling abs and rely on brakes before abs was invented. You assume all personal risks in testing, troubleshooting and determining why abs failed in addition to the brake pedal going to the floor. Perform braking tests carefully and never assume brakes work since you already know the pedal goes to the floor. Brakes are compromised (worse case scenario) with no guarantee they work in everyday driving. As a diyer, you assume these risks. Brake repair shops or GM are your other options if you feel this is beyond you. The vacuum powered brake boost unit isn't the problem, leaving the abs and hydraulic brake system to diagnose.
well I am gonna get brakes looked at in a few weeks. My inspection is Dec so gonna do it all then. The car is not driven much so it can wait until then

thanks for your input
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Old 11-09-2021, 03:34 AM   #17
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Default Re: Brake problem

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Btw, whoever replaced the master cylinder would leave the brake pedal/brake boost push rod as is to eliminate adjusting the push rods. This presumes a straight replacement of one mc with a direct replacement mc so rod adjustment isn't needed. This maintains alignment when brake boost is needed. Is this what occurred or did someone adjust this rod?
no idea. Took it in got it fixed left (I just sat in waiting room for about an hour) Brakes then worked great.


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It's possible although unlikely for anyone to misadjust this rod and have more power assist, overcoming the master cylinder, effectively allowing power assist to push past the design limits of new master cylinder piston seals. This would suggest incorrect rod adjustment and damaging the mc piston seals.

It wouldn't be surprising for this mc to fail. This is in addition to a problem with abs.
well for now I'm leaning to ABS problem because it doesn't work. If i pull ABS fuses and this still happens then I'll let my mechanic look at it. He didn't do the MC replace I took it to a brake shop for that.
...
1999 SL2 DOHC
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Old 11-18-2021, 09:59 PM   #18
PrestonIII
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Default Re: Brake problem

My guess is that the master cylinder is going bad.

To test:

With the engine running, push the brake pedal very easy. When you feel some resistance, wiggle the pedal up and down, again, really easy.

If the pedal slowly travels down towards the floor as you wiggle it, then the master cylinder is failing towards total failure.

Verification:

If you hit the pedal quick and hard, the pedal stays at the top and is firm. Yet the slow and easy method causes it to fall to the floor. This indicates a failing master cylinder.

Why:

There is an umbrella shaped seal inside the master cylinder bore. When you push the pedal, fluid is held below the umbrella and forces back against the umbrella causing it to open further and push out against the cylinder wall creating a very good seal. (That is why hitting the pedal hard makes a good seal). If you don't hit the pedal hard, then the umbrella doesn't expand against the cylinder wall, and fluid can leak past it. (This is the failure wherein the pedal can go to the floor)

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Old 11-19-2021, 12:57 AM   #19
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Default Re: Brake problem

Master cylinders since about 1965 have been dual units. Losing just one cup seal will not allow the pedal to go all the way to the floor, like I think the OP described. It is possible, I suppose, that both cups are failing simultaneously; but real unlikely. Even more unlikely is that they both magically heal themselves so that normal braking is restored.
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