StopTech BBK problem

[Dang94]

Hi Guys,
Just wondering if anyone can help me out with some brakes advice.
I'm having issues with my Stoptech big brake kit i had installed on my 94 SC NSX.
The brake pedal is extremely hard to press and the braking is extremely weak to the point of being dangerous when trying to brake from a high speed.
When i stand on the brake pedal, it applies the brake force really slowly and then it will pinch the brake on the front left wheel and cause it to lock up.
I'm running the standard stoptech street performance pads.
I have had an issue with my ABS system. It start squealing and making noise previously and now i believe it's not working at all.
Does anyone have any idea why my braking performance could be this bad and if it could be related to my ABS issues?

 

[Old Guy]

The brake pedal is extremely hard to press

Does that mean that you press on the brake pedal; but, the brake pedal does not seem to move or has little movement or does that mean that the brake pedal goes through its normal range of motion; but, you don't get much braking action?

If the pedal is not going through its normal range of motion you could have a hydraulics issue which may or may not be related to the Stoptech calipers. I would be more inclined to say not related; but, there are insufficient details. If the pedal range of motion is normal did you go through the Stoptech bedding in procedure and are you sure that the pad or disc surfaces were clean / uncontaminated after installation? Did you do a full front and back replacement of the rotors and calipers or just the front?

When i stand on the brake pedal, it applies the brake force really slowly and then it will pinch the brake on the front left wheel and cause it to lock up.

The first part of that sentence could be consistent with a problem with your brake booster. There are links to .pdf copies of the 1991 service manual on Prime and if you check on page 19-14 there are fairly simple functional tests (no tools required) you can carry out on the brake booster to determine whether it is 'mostly OK' or 'pretty much dead'.

Does the left front lock up completely without any ABS action? If so, then you clearly have an ABS problem and you might want to get that sorted. I have the last version of the ABS system so I am not familiar with the early ABS issues; but, in general ABS systems should fail safe and not reduce braking force. If you have an ABS problem I think it is different from your current lack of brake torque problem.

 

[docjohn]

You really need a healthy brake system for a BBK upgrade to work. Yours is 27 y/o. If you have not refreshed all the wearable components I would consider just upgrading to the newer 2000 and up system which does away with the solenoids..

 

[solidol]

The way you're describing it it sounds like your vacuum brake booster is gone. Need more details. Was everything working fine right before the ST install?

 

[RYU]

Part of installing new brakes is bleeding the system. Old parts (seals and such) will be stressed during this process. You ought to change your master cylinder and/or booster

 

[B2FiNiTY]

good time to change the booster and master.

 

[Dang94]

Does that mean that you press on the brake pedal; but, the brake pedal does not seem to move or has little movement or does that mean that the brake pedal goes through its normal range of motion; but, you don't get much braking action?

If the pedal is not going through its normal range of motion you could have a hydraulics issue which may or may not be related to the Stoptech calipers. I would be more inclined to say not related; but, there are insufficient details. If the pedal range of motion is normal did you go through the Stoptech bedding in procedure and are you sure that the pad or disc surfaces were clean / uncontaminated after installation? Did you do a full front and back replacement of the rotors and calipers or just the front?



The first part of that sentence could be consistent with a problem with your brake booster. There are links to .pdf copies of the 1991 service manual on Prime and if you check on page 19-14 there are fairly simple functional tests (no tools required) you can carry out on the brake booster to determine whether it is 'mostly OK' or 'pretty much dead'.

Does the left front lock up completely without any ABS action? If so, then you clearly have an ABS problem and you might want to get that sorted. I have the last version of the ABS system so I am not familiar with the early ABS issues; but, in general ABS systems should fail safe and not reduce braking force. If you have an ABS problem I think it is different from your current lack of brake torque problem.

Thanks for your input.
The pedal doesn't travel far at all when i press the brake, it feels like a 1-2inch travel and i have to stand on the brakes really hard to pull up. The brakes seemed fine before i did the upgrade, even with the ABS issue.
I assume my mechanic went through the bedding procedure but can't be sure.
I have stoptechs on the front and rear and I did a full replacement of rotors and calipers
The fronts left locks up without any ABS activation and I will upgrading to the NA2 ABS soon.
From what people are saying, sounds like I should replace the master cylinder and booster.

 

[Dang94]

The way you're describing it it sounds like your vacuum brake booster is gone. Need more details. Was everything working fine right before the ST install?

The brakes felt fine before the upgrade. Far better than they are now.
The brake pedal will only travel 1-2 inches and i have to stand on it really hard to pull up.
Sounds like the booster could be the culprit.

 

[Kaz-kzukNA1]

Very likely you lost the vacuum booster assist but you may have multiple issues so be careful.
It's the brake and safety issue.

If master cyl failed or bleeding issue, it would be the other way round.
The pedal would travel further or even sunk to the floor, spongey pedal feeling, etc.

Testing the vacuum assist is easy.

1. Press on the brake pedal several times before starting the engine.
This will release any vacuum left in the system.

2. While keep pressing down on the brake pedal, start the engine.
Don't need applying high brake pressure.
Enough with the pedal pressure just like when you are stopping at the red traffic light.

3. As soon as the engine starts, you should feel the pedal sunk further.
This is the vacuum assist effect.
If not, you need to find the cause and no need carrying out the next step.

4. Once you have confirmed the effect of the vacuum assist, release the brake pedal and don't touch it until after the next step.

5. Stop the engine.

6. Press on the brake pedal at the same pressure multiple times noting the pedal height change at each pedal stroke.
Every time when you press on the pedal, the pedal stroke gets shorter and pedal height gets higher, thus getting closer to you.
This will confirm the vacuum seal.
If the pedal height doesn't change at each stroke, you have bad seal.


Without the vacuum assist, you are like trying to stop the car without running the engine.
Even at walking speed, you will need massive pressure to stop the car.

From what you wrote, you haven't managed to transfer the pad material evenly to the new disc surface yet and if without the vacuum assist, I won't even drive the car.


Kaz

 

[Old Guy]

Kaz has provided you with the functional test for the brake booster that is described in the service manual. Easy to do so you should be able to determine whether you have a booster issue. If the brakes worked normally before you did the upgrade I would not rush out to replace the booster and certainly not the master cylinder. Lack of movement in the pedal is definitely not a master cylinder failure symptom and a booster problem could be as simple as a failed check valve or the vacuum connection to the booster coming loose.

I assume my mechanic went through the bedding procedure but can't be sure.

Highly unlikely. The bedding in procedure requires repeated application of the brakes from high speed which means that the tech is going to have to find a stretch of highway with little or no traffic to do the procedure. I suspect that a lot of owners do their bedding in late at night on a deserted section of highway to avoid causing an accident or getting pulled over by the guys with the red and blue flashing lights because of erratic driving behavior. The requirement for a bedding in procedure depends on the brake pad material. You should read the application data that came with the brake pads or go to Stop Tech's website to review their guidelines for bedding in the pads

Centric_and_APC_Technical_Whitepaper_C4-Bed-In-Performance-8-2018_1.pdf (centricparts.com)

 

[Dang94]

Very likely you lost the vacuum booster assist but you may have multiple issues so be careful.
It's the brake and safety issue.

If master cyl failed or bleeding issue, it would be the other way round.
The pedal would travel further or even sunk to the floor, spongey pedal feeling, etc.

Testing the vacuum assist is easy.

1. Press on the brake pedal several times before starting the engine.
This will release any vacuum left in the system.

2. While keep pressing down on the brake pedal, start the engine.
Don't need applying high brake pressure.
Enough with the pedal pressure just like when you are stopping at the red traffic light.

3. As soon as the engine starts, you should feel the pedal sunk further.
This is the vacuum assist effect.
If not, you need to find the cause and no need carrying out the next step.

4. Once you have confirmed the effect of the vacuum assist, release the brake pedal and don't touch it until after the next step.

5. Stop the engine.

6. Press on the brake pedal at the same pressure multiple times noting the pedal height change at each pedal stroke.
Every time when you press on the pedal, the pedal stroke gets shorter and pedal height gets higher, thus getting closer to you.
This will confirm the vacuum seal.
If the pedal height doesn't change at each stroke, you have bad seal.


Without the vacuum assist, you are like trying to stop the car without running the engine.
Even at walking speed, you will need massive pressure to stop the car.

From what you wrote, you haven't managed to transfer the pad material evenly to the new disc surface yet and if without the vacuum assist, I won't even drive the car.


Kaz

Thanks for that Kaz, Much appreciated. I will get onto it soon.
The brake pedal feels exactly like the engine has turned off. I have stopped driving the car, i almost collided with a SUV on the on ramp of a freeway a few months ago. If the SUV hadn't of seen me coming and got out the way, i would of slammed into him at 65mph. Scary moment.

 

[Dang94]

Kaz has provided you with the functional test for the brake booster that is described in the service manual. Easy to do so you should be able to determine whether you have a booster issue. If the brakes worked normally before you did the upgrade I would not rush out to replace the booster and certainly not the master cylinder. Lack of movement in the pedal is definitely not a master cylinder failure symptom and a booster problem could be as simple as a failed check valve or the vacuum connection to the booster coming loose.



Highly unlikely. The bedding in procedure requires repeated application of the brakes from high speed which means that the tech is going to have to find a stretch of highway with little or no traffic to do the procedure. I suspect that a lot of owners do their bedding in late at night on a deserted section of highway to avoid causing an accident or getting pulled over by the guys with the red and blue flashing lights because of erratic driving behavior. The requirement for a bedding in procedure depends on the brake pad material. You should read the application data that came with the brake pads or go to Stop Tech's website to review their guidelines for bedding in the pads

Centric_and_APC_Technical_Whitepaper_C4-Bed-In-Performance-8-2018_1.pdf (centricparts.com)

Thanks for your help. I will go through the bedding in procedure when i sort out the pedal issue.
Just one thought, I was wondering if the booster issue could be caused by incorrect fitting of the BBK when installed?

 

[Miner]

Thanks for your help. I will go through the bedding in procedure when i sort out the pedal issue.
Just one thought, I was wondering if the booster issue could be caused by incorrect fitting of the BBK when installed?

Always a possibility. If the installer was working around the master cylinder, and disconnected the vacuum line, then failed the reconnect. An old rule of troubleshooting is to look where some type of maintenance was done last.

 

[Dang94]

Always a possibility. If the installer was working around the master cylinder, and disconnected the vacuum line, then failed the reconnect. An old rule of troubleshooting is to look where some type of maintenance was done last.

Cheers, It could a possibility considering everything was fine before the install. I will get everything checked out.