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Soft pedal - brakes go to the floor?

Tiny
TCOB
  • MEMBER
  • 2001 CHEVROLET SILVERADO
  • 6.0L
  • V8
  • RWD
  • AUTOMATIC
  • 100,000 MILES
Feels as if you have barely any braking power to stop, have to anticipate and apply several car links ahead to stop. Found leaking master cylinder and hydro boost also they were changed and still no better, did bench bleed master cylinder and I did bleed hydro boost. Peddle comes back slow and brakes seem to be squeaking some. Can anyone help
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Friday, June 13th, 2014 AT 2:32 PM

42 Replies

Tiny
HMAC300
  • MECHANIC
  • 48,601 POSTS
It probably has air in anti lock unit you'll have to rebleed it and or have a pro do it so he can open the valves on the abs with a scanner. can take up to 3 qts. These guides can help you fix it.

https://youtu.be/w7gUsj2us0U

and

https://youtu.be/WDxvEQrMkBg

and

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

Please run down this guide and report back.
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Wednesday, November 22nd, 2017 AT 11:27 AM
Tiny
TCOB
  • MEMBER
  • 19 POSTS
Thank you. Very helpful to know. I think I went thru that much fluid and no good so again I thank you!
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Wednesday, November 22nd, 2017 AT 11:27 AM
Tiny
CHJONAS
  • MEMBER
  • 2 POSTS
  • 2001 CHEVROLET SILVERADO
Brakes problem
2001 Chevy Silverado V8 Four Wheel Drive Automatic alot miles

I was wanting to know if you can answer my question because I have done everything that I know to do. My brake pedal goes to the floor when my truck is running I have checked for any visible leaks, bled the whole system, and installed a new master cylinder. I even went as far as cleaning out the brake calipers. Nothing seems to help the fact that I have absolutely no brake pedal. I am getting ample amount of fluid to each caliper. Is there any way to adjust the push rod on the brake booster itself? Any help that you can give me will be greatly appreciated. Thanks. It is a vacuum Brake booster, too.
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Monday, February 22nd, 2021 AT 5:26 PM (Merged)
Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 109,645 POSTS
Are you sure there are no leaks at the rear wheel cylenders? Have you checked the rubber brake hoses to the calipers to see if they are expanding when the brake is applied? As far as adjustment, I would suggest double checking to see if there is one on the pushrod. However, I don't believe there is on this vehicle.

Let me know what you find.
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Monday, February 22nd, 2021 AT 5:26 PM (Merged)
Tiny
CHJONAS
  • MEMBER
  • 2 POSTS
Four Wheel Disc Brakes. Braided Stainless lines no rubber ones. In the process of rebuilding all four calipers, but just can't figure out why the brake pedal goes to the floor. When engine is off you can pump the brakes and you can feel the pedal stiffen up but soon as you start it there is absolutely NO pedal. Everything seems to be correct by all the checks in my Haynes manual. Maybe I will stumble across it, soon I hope.
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Monday, February 22nd, 2021 AT 5:26 PM (Merged)
Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 109,645 POSTS
Let me know. If there is no adjustment on the pushrod and nothing is leaking, my guess is you got another bad master cylender. Brakes are really a simple system. You get a pedal, but as soon as you get the assist, you are able to push the pedal to the floor. That sounds like the MC. If there are no leaks, everything is bled, the calipers are good. Fluid then has to be bypassing in the MC.

Do you have 4 wheel disc or rear drum brakes?
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Monday, February 22nd, 2021 AT 5:26 PM (Merged)
Tiny
SPCQUIGGA
  • MEMBER
  • 4 POSTS
It sounds like air in the ABS system. I have the same issue with my truck, this is what I was told it was.
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Monday, February 22nd, 2021 AT 5:26 PM (Merged)
Tiny
PIPERJR
  • MEMBER
  • 2 POSTS
  • 2001 CHEVROLET SILVERADO
  • V8
  • 4WD
  • AUTOMATIC
  • 75,000 MILES
I have replaced my master cylinder, rotors, calipers and completely bled my brake system and still have no pedal I have thoroughly checked for leaks and have none, what am I missing I would love to give a donation but I have just spent 700 bucks and am flat broke will someone please help me out

I tracked it down in searching for leaks but found no bleeder. Do I just crack the line, and if so how to know which one there are 5.
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Monday, February 22nd, 2021 AT 5:26 PM (Merged)
Tiny
RASMATAZ
  • MECHANIC
  • 75,992 POSTS
You need a special tool to bleed it-check the parts store but here is a guide that will help you as well

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

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Monday, February 22nd, 2021 AT 5:26 PM (Merged)
Tiny
PIPERJR
  • MEMBER
  • 2 POSTS
Thank you
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Monday, February 22nd, 2021 AT 5:26 PM (Merged)
Tiny
FRANK VAUGHN
  • MEMBER
  • 2 POSTS
  • 2001 CHEVROLET SILVERADO
  • 6.0L
  • V8
  • 4WD
  • AUTOMATIC
  • 131,000 MILES
My truck is a 2500hd with hydroboost.

I have put on new:
A master cylinder.
An ABS unit.
Complete brake line set.
Calipers.
Rotors.
Pads.
I still have now pedal with the engine running bit a moderate pedal with engine off.
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Monday, February 22nd, 2021 AT 5:26 PM (Merged)
Tiny
MHPAUTOS
  • MECHANIC
  • 31,937 POSTS
Sounds as if you still have air trapped in the hydraulic system. This guide can help you fix it.

https://youtu.be/w7gUsj2us0U

and

https://youtu.be/WDxvEQrMkBg

and

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

Please run down this guide and report back.
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Monday, February 22nd, 2021 AT 5:26 PM (Merged)
Tiny
FRANK VAUGHN
  • MEMBER
  • 2 POSTS
I have done the automated bleed with the scan tool many times, it still does not yield any different results.
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Monday, February 22nd, 2021 AT 5:26 PM (Merged)
Tiny
MHPAUTOS
  • MECHANIC
  • 31,937 POSTS
Is the pedal free play excessive? You only need a few mm or so, excessive pedal free play will give a low pedal.
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Monday, February 22nd, 2021 AT 5:26 PM (Merged)
Tiny
FRANKVAUGH69
  • MEMBER
  • 1 POST
No free play if engine is running the peddle will not return and there is no brakes until you get to the floor
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Monday, February 22nd, 2021 AT 5:26 PM (Merged)
Tiny
MHPAUTOS
  • MECHANIC
  • 31,937 POSTS
Typical of air still trapped in system, you may have one circuit affected, try clamping off all flexi hoses and see if pedal is ok, if so remove one clamp at a time and see what the pedal does.
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Monday, February 22nd, 2021 AT 5:26 PM (Merged)
Tiny
LM7_AR501
  • MEMBER
  • 2 POSTS
  • 2001 CHEVROLET SILVERADO
  • 5.3L
  • V8
  • 2WD
  • AUTOMATIC
  • 230,000 MILES
My brakes keep going out when I fully turn my steering wheel on either side. Brake pedal will get really hard when I completely turn the steering wheel and when I let go of the steering wheel the brake pedal just sinks and brakes go out I have to pump the pedal for them to come back. Works perfectly fine when going straight. I’ve already replaced master cylinder and brake booster and still no difference. Truck does have a cam Not sure if that could be causing problems but I’m just out of luck and can’t find anything on the internet. Any help would be very much appreciated!
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Monday, February 22nd, 2021 AT 5:26 PM (Merged)
Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 109,645 POSTS
Hi,

That is odd. The brakes are a simple hydraulic unit. It shouldn't matter if you are turning the wheel when braking.

Tell me, is it the brake pedal gets hard to push when turning or it goes to the floor? If it goes to the floor, try something. Have a helper turn the wheels and apply the brakes while you watch the rubber brake hoses which attach to the rear of the brake calipers. See if one is expanding. I attached a pic and highlighted what I'm referring to.

Also, let me know if the vehicle has a traditional vacuum brake booster or if it is a hydrostatic system that functions via the power steering pump pressure.

Let me know.

Joe
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Monday, February 22nd, 2021 AT 5:26 PM (Merged)
Tiny
LM7_AR501
  • MEMBER
  • 2 POSTS
When I fully turn I can feel the brake pedal pushing back and getting hard but as soon as I let go of the steering wheel it completely sinks down and I have to press it a few times as I straighten out the steering wheel to get my brakes back. I believe it does have the traditional vacuum brake booster.
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Monday, February 22nd, 2021 AT 5:26 PM (Merged)
Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 109,645 POSTS
Okay, I need to confirm which system you have. Interestingly, the hydro-boost systems show technical service bulletins related to full turns and brakes applying themselves.

Take a look at the pic below. I highlighted a vacuum brake booster. Is that what is located behind the brake master cylinder?

Let me know.
Joe
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Monday, February 22nd, 2021 AT 5:26 PM (Merged)

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