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Q: Lost power to my front brakes but i still have power to the back.

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i feel like i have lost power to my front brakes and am not sure if the are releasing all the way. i feel all the breaking coming from the back end. i have bled all four corners and still have no pressure. the peddle goes all the way to the floor. i am suspecting that it could be the proportioning valve but i am not positive. is there any way to know for sure if it is my PV or could it be my master cylinder?

My car has 160000 miles.
My car has an automatic transmission.

Hello and thank you for your question. When you were able to bleed all four brakes FR, FL, RR, RL, then the proportioning valve is okay. If the valve was sticking, you would not be able to get any fluid out from it.

When you step on the brakes and the pedal goes to the floor and your pedal is spongy, that is a sign of air in the system. Try bleeding all the ports in the vehicle including the master cylinder. Once you have done so, test the brake pedal for any firmness.

If the pedal is still spongy, check all over the brake system for any external leaks. If there are no leaks found, then your master cylinder has failed internally and will not apply correctly.

To verify this condition, press on the brake pedal all the way to the floor and feel the sponginess. Then pump the brake pedal fast. The pedal should start to get firm and then go down to the floor and become spongy again. This means the seals inside the master cylinder are leaking internally.

I recommend replacing the master cylinder and bleeding the vehicle again. If you need assistance with diagnosing your brake system or replacing the master cylinder, then contact a technician, like one from YourMechanic, to assist you.

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