Skip the auto shop - Our mechanics make house calls

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

asked by on

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.

A: Hello and thank you for your question. When...

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.

Was this answer helpful?

Need advice from certified mechanic? Get help now!

Over 1000 mechanics are ready to answer your question.
The statements expressed above are only for informational purposes and should be independently verified. Please see our terms of service for more details

Ask a Mechanic
(100% Free)

Have a car question? Get free advice from our top-rated mechanics.

Ask A Mechanic
Over 10,000 questions answered!

Get an instant quote for your car

Our certified mechanics come to you ・Backed by 12-month, 12,000-mile guarantee・Save up to 30%

Get a quote

What others are asking

Q: Protection mode is blamed for engine shutting down

Hello there, thank you for asking about your 1991 Buick Reatta. What the previous owner is saying could be correct. Resistor sensing contacts are located in the ignition key lock cylinder of your vehicle. When the key is inserted, these...

Q: Rear wheel not turning

If your rear parking brakes were on when you parked the car then it's possible that the parking brake cable or the brake shoes are seized to the brake drum. I recommend having a certified mechanic come and diagnose the...

Q: Brakes not working properly.

This can be caused from several different failed parts. First off the loss of fluid is a major leak in the system and an inspection would be needed to locate the leaking part. I have seen rusted lines causing a...

Related articles

What Causes Hoses to Leak?
While the largest part of your engine is mechanical, hydraulics plays a significant role. You’ll find fluids at work in a number of different areas. Your car's fluids include: Engine oil Transmission...
How to Avoid Back Pain in a Car
If you have back problems, sitting in a car for an extended period of time can be excruciating. Even without back problems, you could experience discomfort and soreness from...
How Much Does a Mechanic Make in Vermont?
Automotive technician jobs in Vermont have an average mechanic salary of $37k, with some mechanics earning a salary of $53k.