Brake Pedal Goes to Floor When Engine Running: Resolved

Brake pedal goes to floor when engine running situation may occur when the brake pedals malfunction. Your brake pedal may sink when the brake fluid leaks or the brake line sucks in the air.

Brake Pedal Goes To Floor When Engine Running

A defective brake booster or master cylinder will also push the brake pedal to the floor. Keep reading to discover how you can detect and fix these issues.

Why Does Your Brake Pedal Go to the Floor When The Engine Is Running?

Your brake pedal goes to the floor when the engine is running because of brake fluid leaks, the air in the brake system, and a broken brake booster. The brake pedal also sinks because of a faulty master cylinder and excessive loss of brake fluid.

– A Brake Fluid Leak

When the brake line wears out, it causes the brake fluid to leak. The brake pedal takes in air from outside and sinks to the floor. The fluid may also leak from the calipers.

As the fluid leaks, the braking system lacks the pressure and force necessary to function. Consequently, the brake pedal goes to the floor when you press it.

– Defective Brake Booster

The brake booster delivers the braking power when you need to stop the car. A malfunction in the booster increases your vehicle’s stopping distance.

Why Brake Pedal Go to the Floor When The Engine Is Running

As the booster wears out further, the car fails to stop when you step on the brake pedal.

A bad brake booster cannot generate enough brake pressure to stop the car, especially in the case of an emergency.

– Insufficient Brake Fluid 

Your vehicle loses braking power as the level of the brake fluid declines. You may get a warning on your dashboard or control module when the level is too low. Ignoring the warning is risky because the braking system may malfunction.

Constant leaks may reduce the brake fluid to an insufficient level that cannot stop the car from causing an accident. Repair leaky brake calipers or brake lines to avoid losing all the fluid.

– Faulty Master Cylinder 

If the question “Why does my brake pedal go to the floor but fluid is full?” crosses your mind, check the cylinder. A functional master cylinder is essential for the car to slow down or stop when you apply the brakes. The cylinder compresses every time you step on the brake pedal, causing the pressure to increase in the brake lines. The car stops because of the high pressure in the master cylinder.

A bad brake master cylinder cannot generate enough fluid pressure to stop or slow down the vehicle. The brakes may become spongy if the seals in the brake cylinder are damaged and leaky. You will have spongy brakes that sink to the floor.

– Air Trapped in the Brake Line 

When you step on the car’s brakes, the brake lines may trap in some air, giving you a spongy feeling. The problem occurs when the brakes are not bled properly after installing a new master cylinder.

Air Trapped in Car Brake Line

The brake pedal should be firm and not spongy. Hence, you can easily tell when the braking system is sucking air from outside.

– Bad Driving Habits 

Aggressive driving can cause your braking system to malfunction. If you like to step on the brakes frequently and suddenly, your brake pedals may become spongy with time. The braking fluid heats up and loses its thick density every time you press the brake pads hard.

If you increase the pressure on the pedal, the fluid becomes thinner. You will feel the pedal sinking to the floor because the brake fluid lacks sufficient power to sustain the braking system.

How Do You Fix Your Brake Pedal Sinking to the Floor?

To fix your brake pedal sinking to the floor, determine if your car has enough fluid to run the braking system. If refilling the fluid does not raise the pedal, check brake lines, master cylinder, and brake booster for defects. Repair the broken parts and recheck the pedal’s position.

– Check and Refill the Brake Fluid 

The brake fluid level should be the first thing you check when the brake pedal goes to the floor with the engine running. Refill the container if the level is low below the standard level. Respond to any signals or warnings of insufficient brake fluid and always keep the level at the recommended level at all times.

The process is simple, but you can also ask your mechanic to refill it. If the fluid level is sufficient, inspect other parts for defects.

– Inspect the Master Cylinder 

The next component to check is the cylinder behind the brake pedal. Check if the seals are worn out and leaky. Stop at the next car service or your mechanic’s shop for a replacement.

Remedies for Brake Pedal Sinking to the Floor

Avoid driving around with a leaky cylinder. If the seals are old but not leaky, you can replace them. However, installing a new cylinder is inexpensive and recommended.

– Check the Brake Lines and Calipers for Leaks 

Brake fluid leaks mostly come from the brake caliper and lines. The leaks lead to an insufficient level of brake fluid in the can. Hence, you need to inspect the brake lines for holes or cuts. The easiest way is to check all the wheels for oil residues indicating leaking brake fluid.

Inspect the bleeder screws and calibers as well for any fluid residues. Your part is to inspect and confirm any leaks. A professional mechanic will help you install new brake lines if necessary to stop the leaks and restore the braking system function.

– Repair the Faulty Brake Booster 

A damaged brake booster requires immediate repair or replacement for your safety. The booster is between the brake pedal and the master cylinder.

Pull out the vacuum tube and press the pedal to repair the booster. If the pedal is back up again and firm, you can reinstall the booster. The braking system may have other broken parts if the booster repair does not fix the sinking pedal.

– Go to a Garage

A functional brake system is essential for your and other road users’ safety. Hence, you need to treat any braking problem as an emergency. If the brake pedal is spongy and on the floor, do not wait for the brakes to fail. Inspect and fix any broken parts immediately.

In addition, pass by a service center to confirm that all parts are working well, including the brake light and pads. It is advisable to change worn-out parts every year to prevent mechanical issues. A good mechanic will detect failing components and replace them during regular maintenance appointments.

To fix a sinking brake pedal, bleed the air out of the system, repair the master cylinder, and fix any fluid leaks. If all else fails, visit your mechanic to inspect any defects in the brake booster, calibers, and brake lines. Ensure that the brake fluid is sufficient, and then test drive.


1. What Causes a Hard Brake Pedal Before Starting the Car? 

A hard brake pedal before starting the car is caused by a malfunctioning electric pump or insufficient power steering fluid. Your car could also be missing a serpentine belt. A broken brake booster, cracked vacuum hose, and failing vacuum pump can also cause a stiff brake pedal.

2. Why Is My Car Brake Pedal Spongy? 

Your car brake pedal is spongy because of the air in the braking system. Pressing the pedal several times removes the air. Other causes include a small master cylinder bore, booster pin gap, a leaky brake hose, contaminated brake fluid, and fluid leaks.

3. Is Hard Braking Harmful? 

Yes, hard braking is harmful to your braking system. The pressure and heat from stepping hard on the brakes damage the brake hose and drive shaft. Constant hard braking can also cause the brake fluid to leak, leading to a sinking brake pedal and other braking issues.

Conclusion of Why Does My Brake Pedal Go to the Floor When Engine Is Running


We have outlined the major causes of a sinking brake pedal and quick solutions to the braking problems.

Here is a quick summary of the main points:

  • A low brake fluid level and air in the system can cause the brake pedal to sink.
  • The brake pedal goes down to the ground if the master cylinder and brake booster are broken.
  • Leaks through broken calipers and brake lines lead to insufficient brake fluid.
  • Hard braking damages the braking system and drive shaft.

Fixing these braking issues is important for your safety. You can use the tips shared here to diagnose and fix a sinking pedal before driving to a mechanic or service center.

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