Brake Pedal Goes to Floor When Engine Running

Leakage in the brake fluid line or damage to any other braking system component results in brake pedal goes to floor when engine running. Readout more to find the fixes for the spongy brake pedal!

Do you feel no brake fluid pressure when car is running? It’s not something that you can’t ignore. It may give you a horrifying driving experience. So, you should consult a mechanic as soon as your car’s brake loses pressure.

There could be several reasons that cause the sinking brake pedal. Based on the basis, the corresponding fix may also vary. This article will discuss all the reasons and related fixes for the soft brakes when running.

brake pedal goes to floor

Causes of brake pedal goes to floor when engine running

There are several reasons for brake problems, such as no pressure You must know all these causes. Below are some most common causes of no pressure on the brake pedal. First of all check your brake pads if you face car brake problems.

1.     Loss of brake fluid

Brake fluid leaks are the most common cause of your car brakes going to the floor when the car is runningThe brake fluid leaks cause power loss. So, your vehicle must have enough braking fluid to provide continuous power to the car’s brake system.

You might be wondering how brake fluid is responsible for the flexible brake system. Let me explain the entire process to you. The brake cylinder compresses whenever you compress the foot on the brake pedal.

Consequently, the brake fluid will start flowing towards the brake caliper. It results in brake caliper sticking and high brake pressure. This higher braking force causes the brake pads to squeeze the brake rotor. It causes friction enough to stop the car.

So, now what do you think? Will brake fluid leak cause the brake pedal to move smoothly? No, it will not be able to induce enough pressure on the brake. Consequently, you’ll experience a spongy brake pedal when your car’s engine is running.

2.     Bad Master Cylinder

Another major reason for the brake pedal sinking is the bad master cylinder. The Master cylinder is responsible for hydraulic pressure that activates the wheels. The complete sealing of this cylinder prevents the fluid from leakage.

However, damage to the seals of the cylinder results in fluid leakage. Consequently, there will be pressure loss hence the soft braking power. And your car’s brakes will lose power and stop.

Due to the poor master cylinder, the brake pedals will either stop or not work at all. So, it’s better to repair the faulty master cylinder as soon as possible.

3.     Air in the Brake Line

Have you ever noticed that your car’s brake pedal loses pressure? However, you are wondering if you have just replaced the master cylinder. The reason is the air in the brake line.

Opposite to brake fluid, the air is compressible and hinders the movement of brake fluid within the brake line. As a result, you may feel no pressure on the brake pedal. Eventually, your car will not stop.

So, you must remove the air from the bar Line. You can do this only by bleeding it properly.

4. Bad Brake Booster

So, there’re chances that you experience a unique problem. For instance, your car brake pedal works properly but get stiff once it reaches the bottom. The reason is a bad brake booster. It’s primarily present between the master cylinder and brake pedal.

A brake booster helps in delivering enough power when you suppress the pedal. So, a good brake booster means you don’t have to put much pressure on the braking system.

Now the question is how you would know that brake booster is the culprit. Well, a higher stopping distance clearly indicates a faulty brake booster.

5. Your driving style

Your driving style could also be why your car brakes go to the floor when the car is running.

For instance, the fluid becomes hotter if you use the brakes more often. A hotter fluid is thinner and doesn’t produce enough pressure for optimum power delivery to the brake pads.

To sum up, riding the brakes and not releasing the parking brake both makes brake pedals hard.

Fixes to no brake pressure when car is running

No brake Pressure

So, now you’re well aware of the primary reasons of less braking power. So, now you might be wondering how you can fix this. That’s why we will now discuss some fixes for this no brake pressure. Let’s discuss all the fixes one by one:

  • Examine if there is fluid leakage: Well, you should check the hoses, brake calipers, and brake lines to identify fluid leakage. After identifying the part from where fluid is leaking, replace that part.
  • Examine brake fluid level: Check if the fluid level in the engine bay is optimum. If it’s low, refill it up to the required level.
  • Bleed the brake system: Have you noticed a very low brake fluid level in the engine bay? It indicates the presence of air within the engine. It means you need to bleed the brake system.
  • Replace Brake Booster: Lastly, inspect the brake booster and replace it if you find any issue with it.
  • Replace Master brake cylinder: You must replace the master brake cylinder as soon as possible you identify any damage to its seal.
  • Disconnect the vacuum hose of the brake booster: Try pressing the pedal after disconnecting the vacuum hose of the brake systems.


1. What are the reasons for spongy brake pedal when engine running?

Some common causes for soft brakes are:

  • Loss of brake fluid from the engine
  • A faulty master brake cylinder
  • Presence of air in the brake line
  • A faulty brake booster
  • Bad driving habits

2. How will you diagnose that the brake master cylinder is faulty? 

Some indicators of a bad brake master cylinder are:

  • Brakes may not work at all
  • Poor Braking system
  • Inconsistent brakes

3. How will you identify a bad brake booster?

You can use several ways to identify the problematic booster, for instance

  • You may feel springy Brake pedals
  • Master cylinder may leak
  • You may find the Brake pedal hard
  • Your car will stop working while the car is running

4. Can you bleed the engine while the car is running? 

No, you should not bleed the engine while the car is running. Follow these steps to bleed car engine:

  • shut off the car engine
  • Press the brake pedal. Keep pressing until you feel heard push.
  • Bleed each caliper until the evacuation of air

5. What’s the repairing cost of a brake system? 

The cost of repairing the brake system depends on the damage that the brake system encountered. However, generally, it may cost you 200-300 USD.

Final thoughts…!!!

Brake pedal goes to floor when engine running is a severe issue that you should fix as soon as you diagnose it. The brakes should receive enough power to ensure proper working.

 Several reasons could cause the brake pedal to sink. For instance, if you feel spongy brakes, brake fluid leakage, or a faulty master cylinder, consult the mechanic shortly to fix brake pedal . Most probably, the mechanic will replace the defective engine parts.


Shafiqule Islam is a graduated Mechanical Engineer. He has both on hand and managerial job experience of 15 years in automobile maintenance field. He served as Captain in Electrical and Mechanical Engineering Corp of Army, Technical Head in Taxi Cab business, Head of Plant in Car assembly plant. He is writing automotive contents to share his expertise knowledge to car lovers for solving their vehicle issues.

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