Brakes not working properly and pedal goes to the floor why?

Hello, I am Danny,

It sounds like you are having trouble with the master cylinder. These will wear out with time due it being constantly used (brakes applied). I have attached a tutorial showing what is involved for its replacement. I would suspect there is air in the lines. 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 these guides and report back. Hope this helps and thanks for using 2CarPros.
Danny-

Replaced front disk pads and calipers also master cylinder. Rear okay. Bled all four wheel/brakes, but still no brakes and little pressure on front drive side.

You must bench bleed the master before you install it. Here are guides to help you bleed the master:

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

and

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

Please let us know what happens.

Cheers, Ken

Also, if you have ABS the module needs to be bled. You need a scan tool to bleed the module or you will never get rid of the air.

Roy

Bleeding the ABS System
Perform a manual or pressure bleeding procedure. If the desired brake pedal height results are not achieved, perform the automated bleed procedure below.
The procedure cycles the system valves and runs the pump in order to purge the air from the secondary circuits normally closed off during normal base brake operation and bleeding. The automated bleed procedure is recommended when air ingestion is suspected in the secondary circuits, or when the BPMV has been replaced.

Automated Bleed Procedure

Notice: The Auto Bleed Procedure may be terminated at any time during the process by pressing the EXIT button. No further Scan Tool prompts pertaining to the Auto Bleed procedure will be given. After exiting the bleed procedure, relieve bleed pressure and disconnect bleed equipment per manufacturers instructions. Failure to properly relieve pressure may result in spilled brake fluid causing damage to components and painted surfaces.

1. Raise the vehicle on a suitable support. Refer to Vehicle Lifting.
2. Remove all four tire and wheel assemblies.
3. Inspect the brake system for leaks and visual damage. Refer to Brake Fluid Loss or Symptoms - Hydraulic Brakes. Repair or replace as needed.
4. Inspect the battery state of charge.
5. Install a scan tool.
6. Turn ON the ignition, with the engine OFF.
7. With the scan tool, establish communications with the EBCM. Select Special Functions. Select Automated Bleed from the Special Functions menu.
8. Bleed the base brake system.
9. Follow the scan tool directions until the desired brake pedal height is achieved.
10. If the bleed procedure is aborted, a malfunction exists. Perform the following steps before resuming the bleed procedure:
^ If a DTC is detected, refer to Diagnostic Trouble Code (DTC) List and diagnose the appropriate DTC.
^ If the brake pedal feels spongy, perform the conventional brake bleed procedure again.
11. When the desired pedal height is achieved, press the brake pedal in order to inspect for firmness.
12. Remove the scan tool.
13. Install the tire and wheel assemblies.
14. Inspect the brake fluid level.
15. Road test the vehicle while inspecting that the pedal remains high and firm.

I have replaced this car with new pads calipers master cyl rear wheel cyl also front rotors but I still have a low brake pedal along with the front calipers not releasing. What could be the problem after bleeding the system and I've also replace the front brake hoses. Rear brakes work fine. Can you Help. Thanks Dan Leake.

You may want to try a pressure bleeder. Once air gets into the ABS system, it can be real hard to get out. Some have to be bled electronically with a scan tool.

Brake pedal can be pumped to firm while engine is off, but goes to the floor and pumping does nothing once the engine is started. I changed rotors and pads on the front of my car listed above LS model. I collapsed the caliper cylinder with bleeding screw open on the left, while on the right I did it without opening the bleeding screw. Then I bled the left side. Now I have no brakes. There are no leaks anywhere. Please help.

If all you did was replace pads and rotors and now this is happening then we most likely have air in the lines. I understand that you can release the caliper by breaking the bleeder loose but it is not a good idea to open the system as you will let air in and then it is required to bleed the whole thing.

Here is a guide that will help with that:

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

The best way to compress the caliper is with a piston compressing tool that basically forces the fluid back to the reservoir.

After you bleed all the brakes starting with the right rear, left rear, right front, and left front and it still goes to the floor, we need to go through this guide:

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

Let us know what you find and we can go from there. Thanks