Q: Brake pedal sinks

asked by on October 09, 2016

Brake pedal sinks, I added fluid, it wasn't very low.brakes was good before. It keeps taking fluid. I haven't seen any signs of leaks at calipers, master cylinder, or under dash. Pedal will feel good when sitting if I pump it. Once key is turned it sinks. And yes my check engine soon light comes on shortly after driving. Could this be the master cylinder?

My car has 82000 miles.
My car has an automatic transmission.

Brake pedal is lower than usual Inspection $79.99 - $89.99 Get a Quote

This is a sign of a potential vacuum leak in the brake booster. When there is not enough vacuum in the brake booster, this will cause a hydraulic pressure drop resulting in a soft brake pedal. If you’d like, a certified YourMechanic technician can come to your location and help you with a Brake pedal is lower than usual Inspection to confirm that this is the issue, and also help to perform a Brake Booster Vacuum Pump Replacement to repair this issue.

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

Problem with noisy brakes

Depending on what part you purchased, you might be ok. Brakes usually only make noises if they are installed incorrectly, or if the friction material (brake pads) are not solidly connecting to the rotors. If the rotors have high spots...

2004 Ford escape motor swap

Hi Chase. Thanks for your question today. Unfortunately, we really can't help you with this, as it's not a service that our mobile mechanics offer or something we specialize. Your best option is to try to locate a Ford engine...

Change engine oil soon

This change oil soon light is telling you it is time to get the oil and filter changed. Whoever changes the oil and filter for you will need to reset the light for you so you can start fresh until...

How often should my tires be rotated?

Since tires are such an important part of your driving experience, it is crucial that you have the rotated whenever they are scheduled for maintenance. To tell how often your tires should be rotated. Follow the recommended service schedule...

How can I tell if it's my timing chain or something else?

Hi, thanks for writing in. Unfortunately, I will need a bit more information before confirming if the issue lies in your timing chain or not. Your car can certainly run and start with a timing issue, however it is not...

new ac compressor now not energizing clutch

Hello. From what you describe, it sounds like there may be some sort of issue with the clutch pressure / cycling switch. These switches are responsible for activating the compressor when they detect that the pressure is at or temperature...

The brakes won't bleed in my 2000 Ford Expedition

This vehicle has anti-lock brakes and the ABS hydraulic control unit is blocking fluid flow to the rear brakes, preventing you from bleeding out the air that got into the system when the line broke. You will need to use...

Spark plug hole stripped

Sometimes the hole can be saved, and sometimes it cannot. Methods for repairing the hole include chasing it with a tap, or using a HeliCoil kit. A HeliCoil is a coil-wire insert used to create new threads in the cylinder...

Question about buying radiator for 1999 ford ranger v4 2.5l

Hi Javier. Thanks for the question today. In cases like this, you want to replace what you currently have active, as it's possible that the previous owner has removed the OEM transmission cooler, which may be the reason for the...

Related articles

P0140 OBD-II Trouble Code: O2 Sensor Circuit No Activity Detected (Bank 1, Sensor 2)
P0140 code definition O2 Sensor Circuit No Activity Detected (Bank 1, Sensor 2) What the P0140 code means P0140 is the OBD-II...
P0330 OBD-II Trouble Code: Knock Sensor 2 Circuit Malfunction (Bank 2)
P0330 code definition P0330 is a general OBD-II trouble code that is indicating a malfunction in the knock sensor circuit 2. Note:...
P0156 OBD-II Trouble Code: 02 Sensor Circuit Malfunction (Bank 2 Sensor 2)
P0156 P0156 trouble code definition Oxygen Sensor Circuit Malfunction (Bank 2 Sensor 2) What the P0156 code means The purpose of the oxygen sensor is to monitor the amount of oxygen present in the exhaust and relay this information to...