Brake pedal goes to the floor

Tiny
MIKE DESROSIERS
  • MEMBER
  • 2004 CHEVROLET SILVERADO
  • V8
  • 2WD
  • AUTOMATIC
  • 132,000 MILES
I replaced my pads on my 2004 chevy silverado and bled the brakes. I know I did all this right. The brakes are fine until I turn the car on. Then the brakes go right to the floor like the system is full of air. I have 130K+ on this truck and hear that they were made with faulty master cylinders. I can change that very easily. My question is how do I know it is not the brake power booster unit. Is there a way to check the master cyl vs the power unit. Thanks for your help,
Mike
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Sunday, August 21st, 2011 AT 4:28 PM

31 Replies

Tiny
2CEXPT
  • MEMBER
If you're not leaking anywhere-and is sinking to the floor-replace the master cylinder,its not coming from the booster.

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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Sunday, August 21st, 2011 AT 4:30 PM
Tiny
MIKE DESROSIERS
  • MEMBER
I have thoroughly checked for leaks (thinking that was the problem).
I will replace the master cyl and start from there.
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Sunday, August 21st, 2011 AT 4:48 PM
Tiny
MIKE DESROSIERS
  • MEMBER
I do have a question about bleeding the brakes on this truck. Should I try bleeding the brakes with the power on or with the truck running?
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Sunday, August 21st, 2011 AT 5:25 PM
Tiny
2CEXPT
  • MEMBER
You can follow this guide explains is perfectly.

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

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Sunday, August 21st, 2011 AT 5:31 PM
Tiny
MIKE DESROSIERS
  • MEMBER
I ordered a new master cylinder from Autozone (they were the only ones that could get it for me the same day). I received it at 5:30 pm Sunday night. After I bench bled the new master cylinder per the new manufacturer instructions, I installed the MC. I bled the brakes, and I have done many disc and drum brake jobs over the years for my family and I (and we are all still alive), and the same problem still exists. The brakes get hard when we are sitting there bleeding them, but once I start the engine, they go straight down to the floor I have checked thoroughly for leaks and have not found any. Since I have replaced the master cylinder (MC), it seems like the only choice left is the power booster. Yet, a problem like this sure seems like there is air somewhere in the lines. It seems like there is a possibility that there is some sort of leak that I am not able to detect. I am thinking that my next move is to take it to a brake shop and get the system vacuum bled. What are your thoughts with my problem?
Thanks,
Mike
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Monday, August 22nd, 2011 AT 3:46 AM
Tiny
2CEXPT
  • MEMBER
You may need a scanner to open the valve in the ABS while bleeding I have seen this problem before.
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Monday, August 22nd, 2011 AT 6:04 AM
Tiny
MIKE DESROSIERS
  • MEMBER
You were right I took the truck to the shop and they had to used their scanner to open the valve to get the air out, All fixed thanks again for you help.
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Monday, August 22nd, 2011 AT 3:36 PM
Tiny
2CEXPT
  • MEMBER
Glad you could get it fixed, that kind of problem can be tough. Please use 2CarPros anytime we are here to help

Cheers
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Monday, August 22nd, 2011 AT 5:26 PM
Tiny
APRYLBAKER
  • MEMBER
  • 2004 CHEVROLET SILVERADO
  • 5.3L
  • V8
  • 4WD
  • AUTOMATIC
  • 140,000 MILES
I changed out the brake lines, the master cylander and the booster. There are not front brakes. I used the computer to test the ABS module. It is working. I manually bled the master cylander. I bled all four wheels. Still no brakes. Not sure what is causing it with everything brand new. It's getting fluid. It will pump up when the car is off, but as soon as it's started, it goes to the floor.
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Monday, February 22nd, 2021 AT 5:22 PM (Merged)
Tiny
ASEMASTER6371
  • EXPERT
Good afternoon,

Since you have a scan tool, I would do the automated bleed procedure for the ABS module. Sounds like you have air in the ABS module.

Roy

ABS Automated Bleed Procedure

Notice: When adding fluid to the brake master cylinder reservoir, use only Delco Supreme 11, GM P/N 12377967 (Canadian P/N 992667), or equivalent DOT-3 brake fluid from a clean, sealed brake fluid container. The use of any type of fluid other than the recommended type of brake fluid, may cause contamination which could result in damage to the internal rubber seals and/or rubber linings of hydraulic brake system components.

Notice: Refer to Brake Fluid Effects on Paint and Electrical Components Notice in Service Precautions.

Important: This procedure may be performed on all vehicles EXCEPT those equipped with option code JL4, Vehicle Stability Enhancement System (VSES).

Important: The base hydraulic brake system must be bled before performing this automated bleeding procedure. If you have not yet performed the base hydraulic brake system bleeding procedure, refer to Hydraulic Brake System Bleeding (Manual) Hydraulic Brake System Bleeding (Pressure) in Hydraulic Brakes before proceeding.

1. Install a scan tool to the vehicle.
2. Start the engine and allow the engine to idle.
3. Depress the brake pedal firmly and maintain steady pressure on the pedal.
4. Using the scan tool, begin the automated bleed procedure.
5. Follow the instructions on the scan tool to complete the automated bleed procedure. Release the brake pedal between each test sequence.
6. Turn the ignition OFF.
7. Remove the scan tool from the vehicle.
8. Fill the brake master cylinder reservoir to the maximum-fill level with Delco Supreme 11 GM P/N 12377967 (Canadian P/N 992667) or equivalent DOT-3 brake fluid from a clean, sealed brake fluid container.
9. Bleed the hydraulic brake system. Refer to Hydraulic Brake System Bleeding (Manual) Hydraulic Brake System Bleeding (Pressure) in Hydraulic brakes.
10. With the ignition OFF, apply the brakes 3-5 times, or until the brake pedal becomes firm, in order to deplete the brake booster power reserve.
11. Slowly depress and release the brake pedal. Observe the feel of the brake pedal.
12. If the brake pedal feels spongy, repeat the automated bleeding procedure. If the brake pedal still feels spongy after repeating the automated bleeding procedure inspect the brake system for external leaks. Refer to Brake System External Leak Inspection in Hydraulic Brakes.
13. Turn the ignition key ON, with the engine OFF; check to see if the brake system warning lamp remains illuminated.
14. If the brake system warning lamp remains illuminated, DO NOT allow the vehicle to be driven until it is diagnosed and repaired. Refer to Symptoms - Hydraulic Brakes.
15. Drive the vehicle to exceed 13 kph (8 mph) to allow ABS initialization to occur. Observe brake pedal feel.
16. If the brake pedal feels spongy, repeat the automated bleeding procedure until a firm brake pedal is obtained.
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Monday, February 22nd, 2021 AT 5:22 PM (Merged)
Tiny
APRYLBAKER
  • MEMBER
I will try that, thanks.
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Monday, February 22nd, 2021 AT 5:22 PM (Merged)
Tiny
ASEMASTER6371
  • EXPERT
Okay, then you will need a pressure bleeder. That is where you put an adapter on top of the master cylinder and apply air pressure to the fluid. Then open the bleeders one by one until all the air is out.

You have air trapped in the lines and the foot method of bleeding is not enough to get the air out of the system.

Roy
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Monday, February 22nd, 2021 AT 5:22 PM (Merged)
Tiny
APRYLBAKER
  • MEMBER
I will try that, thanks.
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Monday, February 22nd, 2021 AT 5:22 PM (Merged)
Tiny
ASEMASTER6371
  • EXPERT
You are welcome.

Always glad to help.

Roy
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Monday, February 22nd, 2021 AT 5:22 PM (Merged)
Tiny
EMMA ADAMS
  • MEMBER
  • 2004 CHEVROLET SILVERADO
  • 5.3L
  • V8
  • 4WD
  • AUTOMATIC
  • 180,000 MILES
I put new brake lines new rotors, calipers, pads, bled the master cylinder. I have ABS brakes. I bought a scanner tool I bled the ABS system. Also, when the engine is off I got full pedal, when the engine is running I push on the pedal it goes to the floor.
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Monday, February 22nd, 2021 AT 5:22 PM (Merged)
Tiny
ASEMASTER6371
  • EXPERT
Good evening,

This sounds like you still have air in the system.

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

When you bled the system, did you use a pressure bleeder? With it being a truck, using someone to push the pedal will not force the air out of the system.

I would rent a pressure bleeder and bleed the system.

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

I also noticed you did not replace the master cylinder. That may be the issue.

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

Roy
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Monday, February 22nd, 2021 AT 5:22 PM (Merged)
Tiny
SHERIHOJEM
  • MEMBER
  • 2003 CHEVROLET SILVERADO
  • 4.3L
  • V6
  • 2WD
  • AUTOMATIC
  • 160,000 MILES
Replaced all four brake pads and rotors, calipers, master cylinder, booster, ABS pump and control, bled brakes many times, still brake pedal going to floor. No pressure, brake lines not leaking. Please hep
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Monday, February 22nd, 2021 AT 5:22 PM (Merged)
Tiny
ASEMASTER6371
  • EXPERT
Good morning,

Did you bench bleed the master before installing?

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

You most likely have air in the ABS unit. You need a scan tool to do the automated bleed procedure. I attached the procedure for you.

Roy

Change Vehicle Bookmarks Library Request Conversion Calculator Technician's Reference - Collision

brake bleeding
44
Community 26 Create Quote
2003 Chevy Truck C 1500 Truck 2WD V6-4.3L VIN X
ABS Automated Bleed Procedure
Vehicle Brakes and Traction Control Hydraulic System Brake Bleeding Service and Repair Procedures ABS Automated Bleed Procedure
ABS AUTOMATED BLEED PROCEDURE
Antilock Brake System

Repair Instructions

ABS Automated Bleed Procedure

Note: When adding fluid to the brake master cylinder reservoir, use only Delco Supreme 11(r), GM P/N 12377967 (Canadian P/N 992667), or equivalent DOT-3 brake fluid from a clean, sealed brake fluid container. The use of any type of fluid other than the recommended type of brake fluid may cause contamination which could result in damage to the internal rubber seals and/or rubber linings of hydraulic brake system components.

Note: Refer to Brake Fluid Effects on Paint and Electrical Components Notice in Cautions and Notices.

Important: This procedure may be performed on all vehicles EXCEPT those equipped with option code JL4, Vehicle Stability Enhancement System (VSES).

Important: The base hydraulic brake system must be bled before performing this automated bleeding procedure. If you have not yet performed the base hydraulic brake system bleeding procedure, refer to Hydraulic Brake System Bleeding (Manual) Hydraulic Brake System Bleeding (Pressure) in Hydraulic Brakes before proceeding.

1. Install a scan tool to the vehicle.
2. Start the engine and allow the engine to idle.
3. Depress the brake pedal firmly and maintain steady pressure on the pedal.
4. Using the scan tool, begin the automated bleed procedure.
5. Follow the instructions on the scan tool to complete the automated bleed procedure. Release the brake pedal between each test sequence.
6. Turn the ignition OFF.
7. Remove the scan tool from the vehicle.
8. Fill the brake master cylinder reservoir to the maximum-fill level with Delco Supreme 11(r) GM P/N 12377967 (Canadian P/N 992667) or equivalent DOT-3 brake fluid from a clean, sealed brake fluid container.
9. Bleed the hydraulic brake system. Refer to Hydraulic Brake System Bleeding (Manual) Hydraulic Brake System Bleeding (Pressure) in Hydraulic brakes.
10. With the ignition OFF, apply the brakes 3-5 times, or until the brake pedal becomes firm, in order to deplete the brake booster power reserve.
11. Slowly depress and release the brake pedal. Observe the feel of the brake pedal.
12. If the brake pedal feels spongy, repeat the automated bleeding procedure. If the brake pedal still feels spongy after repeating the automated bleeding procedure inspect the brake system for external leaks. Refer to Brake System External Leak Inspection in Hydraulic Brakes.
13. Turn the ignition key ON, with the engine OFF; check to see if the brake system warning lamp remains illuminated.
14. If the brake system warning lamp remains illuminated, DO NOT allow the vehicle to be driven until it is diagnosed and repaired. Refer to Symptoms - Hydraulic Brakes in Hydraulic Brakes.
15. Drive the vehicle to exceed 13 kph (8 mph) to allow ABS initialization to occur. Observe brake pedal feel.
16. If the brake pedal feels spongy, repeat the automated bleeding procedure until a firm brake pedal is obtained.
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Monday, February 22nd, 2021 AT 5:22 PM (Merged)
Tiny
IVY KING
  • MEMBER
  • 2003 CHEVROLET SILVERADO
  • 5.3L
  • V8
  • 4WD
  • AUTOMATIC
  • 190,234 MILES
Blew a brake line replaced brake line and pedal bled all brakes starting at the passenger rear. No air was coming out any more but still do not have brakes.
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Monday, February 22nd, 2021 AT 5:23 PM (Merged)
Tiny
CARADIODOC
  • EXPERT
I assume the symptom is the brake pedal goes too far to the floor. If that is what is happening, the best suspect is the master cylinder was damaged. Crud and corrosion builds up in the lower halves of the bores where the pistons do not normally travel. When surprised by a sudden leak, we almost always push the pedal as far as possible, and that runs the rubber lip seals over that crud and can rip them. The same thing happens when do-it-yourselfers pedal-bleed improperly with a helper. Pushing the brake pedal over half way is likely to damage the master cylinder. This does not apply to a master cylinder that is less than about a year old.

Also, if the reservoir was run empty, and the truck has four-wheel-anti-lock brakes, you may need to bleed the system with a scanner. That will allow you to command the computer to open two valves to allow those chambers to be bled. If you have rear-wheel-ABS (RWAL), which used to be more common on trucks, no special procedure is needed when bleeding those vehicles.

If you need to replace the master cylinder and the truck does not have four-wheel-ABS, I can share a trick so you do not have to bleed at the wheels. This also works with ABS if you never let the reservoir run empty so there is no air in the hydraulic controller.
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Monday, February 22nd, 2021 AT 5:23 PM (Merged)

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