Q: Brake pedals not firm halfway down

asked by on May 19, 2016

My car's brakes have been fine until now. Recently, however, the brakes seem to "fade", or not have as much pressure when the brake pedal is halfway down. It will then firm up again. This happens when I'm driving. If the car is shut off, the pedal pump has plenty of pressure and stays firmly up. I guess that means the hydraulic part of it is fine.

I thought maybe the vacuum assist was the problem, since the problem only happens when vacuum is applied. I replaced the power assist, but the problem remains. The only other thing I can think of would be the master cylinder, but the pedal is fine when the engine is off. Why are my brakes or brake pedal less firm while driving?

Brake pressure is uneven Inspection $79.99 - $89.99 Get a Quote

Lack of brake power assist would typically result in a hard brake pedal, not one that sinks to the floor. My guess is that the master cylinder is faulty. A bad master cylinder will often result in a pedal that sinks to the floor.

Whatever the cause, this is a potentially dangerous situation that should be inspected firsthand by a professional. I suggest you contact the team at YourMechanic to inspect your uneven brake pressure since we make house calls.

The statements expressed above are only for informational purposes and should be independently verified. Please see our terms of service for more details

Get an instant quote for your car

Our certified mechanics come to you ・Backed by 12-month, 12,000-mile guarantee・Fair and transparent pricing

What others are asking

Blinker clicks too fast

The blinker issue is likely a burnt out bulb or a flasher relay. You can turn on your flashers/hazards to verify bulb operation. If all the bulbs work then you may need a new flasher relay. A left mirror...

Brake bleeding problems

You are going to need to have the ABS module put into bleed function using a scanner that can enable this function or have a mechanic that has a scanner (with this function) and a pressure bleeder to pressure bleed...

I have a 2002 ford focus 1.6 zetec it died when I was driving I have replace the coil pack and checked fuses and have no spark

Hi there. Sometimes when oil splatters under the hood, it can and often will cause damage to electrical harnesses and connections that control many ignition system components. The most common is the crankshaft position or cam position sensor. If these...

I changed my oil pump and now when I try to start it it only clicks once

Unfortunately you have already damaged the motor running the engine until it dies when it lost oil pressure. The bearings for the crankshaft and camshaft have been starved of oil and seized the engine. You will need to have the...

I have a 2013 BMW M5 41.5kmi on it: is it necessary to replace rotors when replacing brake pads?

Thanks for writing in about your BMW M5. The rotors should be checked to be correct thickness. They should only be replaced if they're damaged or below the minimum thickness. If you're unsure if you're rotors need to be replaced,...

Car won't start but the engine turns over

Hi there. There are several reasons for a no start condition. It could be a timing belt if the engine turns over faster than usual. It could be a fuel pump, even though it is heard (pressure not within specification)....

Getting a Check engine light and codes

These codes are related to intake air ports not opening and closing at proper times. This can be related to carbon buildup inside the intake, a vacuum leak, or a faulty electric solenoid depending on the setup. I would start...

When my car is idling the rpms and battery gauge drop off and it acts like it wants to die.

Hello Nick, What are you are describing sounds like potentially a dirty or failing idle air control valve which reads the air intake into the engine. The computer uses this data to make adjustments to the air/fuel ratio to keep...

Too much vibration from the engine when I stop on the road during drive, I hear some sound when I make a left turn.

You could have both of those problems. The ticking sound when you turn is most likely the CV joint. As for the vibration at a stop, an engine mount will usually show signs while driving as well, but not always....

Related articles

How Long Do Brake Rotors Last?
Brake rotors, sometimes called discs, are an important component of the braking system on any vehicle. The brake rotors are the part of...
How to Handle a Car With Total Brake Failure
Brake Brake failure is terrifying and most motorists consider it to be a worst-case scenario. Here are a few things to keep in mind in case you find yourself in such a situation. Awareness of your surroundings is key....
How to Replace a Proportioning Valve
The brakes on the rear wheels may lock up when the brake is applied especially when surfaces are wet if the proportioning valve is failing.