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Brake issue

Tiny
MR2000BRAVADA
  • MEMBER
  • 2000 OLDSMOBILE BRAVADA
  • 4.3L
  • 6 CYL
  • 4WD
  • AUTOMATIC
  • 126,500 MILES
I recently had to replace my master cylinder. I've been flooded bled the brakes and still goes to the floor. I've also had to replace one caliper it was bled. Everything on the system worked before and now I just can't get it to build any brake pressure.
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Sunday, June 20th, 2021 AT 9:34 AM

15 Replies

Tiny
ASEMASTER6371
  • MECHANIC
  • 52,797 POSTS
Good afternoon,

Did you bench bleed the master cylinder first before installing?

https://www.2carpros.com/articles/how-to-replace-a-brake-master-cylinder

You also need to do the automated bleed procedure for the ABS unit. You will need a scan tool that can perform this procedure. Without it, you cannot get the air out of the unit.

https://www.2carpros.com/articles/how-to-bleed-or-flush-a-car-brake-system

https://www.2carpros.com/articles/brake-pedal-goes-to-the-floor

I attached the procedure below.

Roy
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Sunday, June 20th, 2021 AT 12:32 PM
Tiny
MR2000BRAVADA
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Here's what I've done in order:

New Master cylinder was bench bled.
Installed new calipers, both were iffy at best. New lines to front calipers.
Bled entire system as per your service guide. Manually, then tried vacuum bleeding. Still no pressure. Replaced Master cylinder again. With new unit. Followed same bleeding process. Nothing. Used my Tech2 scanner to do automated bleed then vacuum bled entire system again. Still nothing. I'm completely stumped. In 30 years of being a mechanic I've never had one do this. I have no DTC codes, brake light is out as is abs warning light. And yes they have been checked to make sure they light. I'm at the end of my knowledge.
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Sunday, June 20th, 2021 AT 6:27 PM
Tiny
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Okay, try this:

Use vice grips and clamp off all the rubber brake lines.

After that, see if you have a pedal.

If you do then release one pair at a time until you lose the pedal. That will tell you that there is something at that wheel not allowing a brake pedal.

If there is still no pedal, then it is from either the master, as I doubt it since you replaced it 2 times, or the ABS unit itself.

As far as bleeding, I suggest a pressure bleeder. It forces the fluid through the lines and if there is still air, it will force the fluid out the bleeders.

Roy
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Monday, June 21st, 2021 AT 1:48 AM
Tiny
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Cool, I will give it a try this afternoon. Pressure bleed as soon as I can get my hands on a pressure bleeder. Mine has gone missing for a while now. Thanks, will get back to you this afternoon.
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Monday, June 21st, 2021 AT 3:56 AM
Tiny
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You are welcome.

Look forward to hearing an update.

Roy
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Monday, June 21st, 2021 AT 3:57 AM
Tiny
MR2000BRAVADA
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Okay, took the time to try your idea. Clamped off the rubber line helped some. Pedal still goes down quite a ways but it doesn't go to the floor. I have access to a know good ABS unit from a 2000 bravada parts car. Its has the 2 not the K in the 11th VIN position. Both were made in Moraine. Which makes a big difference on parts I've learned the hard way. Is it worth trying if so what's the do and don't on this vin stall. Never had the pleasure of changing the thing.
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Monday, June 21st, 2021 AT 5:33 AM
Tiny
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Sure. Remember, it will need to be flashed to your car's VIN number.

I attached the procedure for the replacement below for you. Make sure you do the automated bleeding again when you are done.

https://www.2carpros.com/articles/how-to-replace-a-abs-controller

Roy

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Monday, June 21st, 2021 AT 2:20 PM
Tiny
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What is having it flashed? I just noticed I have two broken pins in my tech2 on the main plug on the scanner itself. When it rains it pours.
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Monday, June 21st, 2021 AT 3:10 PM
Tiny
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Because the used module is for another car with a different VIN number. It will not function and the ABS light will always be on.

Roy
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Monday, June 21st, 2021 AT 4:37 PM
Tiny
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Sorry I misunderstood the question. Of course. Yep and now I have to find someone with a tech2 as mine I noticed has 2 broken pins in the 32 pin connector. So it fails the self test # 8 RTC. If it isn't one thing it's another.
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Monday, June 21st, 2021 AT 4:45 PM
Tiny
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I agree.

Keep me updated with the results.

Roy
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Monday, June 21st, 2021 AT 4:50 PM
Tiny
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Will do thanks Roy you been a huge help.
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Monday, June 21st, 2021 AT 5:42 PM
Tiny
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You are welcome.

Always glad to help.

Roy
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Monday, June 21st, 2021 AT 7:23 PM
Tiny
MR2000BRAVADA
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I should know something more a little bit today. I've had to work on my backup car the last two days at a fuel pump go out in a 1997 Ford Escort fortunately it was easy to change but just the time so I should be back to you hopefully sometime this evening.
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Wednesday, June 23rd, 2021 AT 9:40 AM
Tiny
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Sounds great.

Look forward to hearing from you.

Roy
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Wednesday, June 23rd, 2021 AT 9:42 AM

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