Find Out Why Your Brake Pedal Goes to Floor When Engine Running

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brake caliper

It can be quite a terrifying feeling when you’re driving along at a high speed and you press the brakes only to feel the brake pedal go to the floor. This is a serious problem, to say the least. People are hesitant to drive around with a vehicle without functioning brakes.

When you apply the brakes, your pedal will not go all the way down if everything is in working properly with your car.

When it comes to braking, the brake pedal is sensitive and follows the amount of pressure applied. If your brake pedal doesn’t have enough force when pressed and goes all the way to the floor with modest pressure, or if it’s mushy, there’s a problem.

The most common reason that your brake pedal sinks to the floor is a brake fluid leak resulting in a loss of brake fluid pressure.

What causes a brake pedal to go to the floor?

brake line flex hoses

There are a number of problems that could be causing your brake pedal to go all the way down when using it. It’s important not to ignore the problem. In fact, this is something you should have inspected right away if it happens. Following are some of the most common reasons why a brake pedal goes to the floor:

Loss of brake fluid

Brake fluid is extremely crucial for improving or maintaining a high brake power. When the driver applies pressure to the brake pedal, the piston in the brake cylinder is compressed. This increase in pressure inside the lines causes the brake fluid particles to move to the caliper. Because of high pressure in the brake fluid, the brake pads squeeze into the rotors causing friction resulting in the vehicle stopping.

When the brake fluid level decreases in between the recommended amount, there’s a significant drop in pressure. If you have a brake fluid leak, you’ll feel your brake pedal going to the floor because there isn’t enough force to compress the piston.

Bad brake master cylinder

In most cases, the brake pedal should feel firm under your leg since it is linked to the master cylinder via a push rod. Hydraulic pressure is generated by the master cylinder to activate brakes and distribute fluid to the front and rear wheels.

The master cylinder must be sealed to maintain pressure and power, which pushes brake fluid to the calipers. As a result, if the rubber seals that keep the brake fluid inside are shredded or worn away, it will cause internal leaking, resulting in a spongy feel under your leg.

Bad brake booster

You might have a failed brake power booster if the brake pedal goes to the floor but still stops. The role of the power booster in braking is to provide assist when the driver applies pressure on the pedal. As a result, stopping the vehicle does not require that much force. The brake booster is attached between the master cylinder and the brake pedal and linked to the engine.

A vacuum line is used to counteract fluid pressure in the braking system. You will notice that stopping distances are longer when the brake booster is faulty. To stop the car completely, you must apply maximum force to the pedal. This happens because you do not have enough power for your vehicle to come to a halt.

Air in brake lines

After changing the master cylinder, many drivers have reported that the brake pedal suddenly goes to the floor. This happens most usually if no air bleeding was done after replacing a new master cylinder, resulting in air in the brake lines. The air prevents effective circulation of brake fluid within the brake lines, causing damage to the lines and producing a spongy brake pedal feeling instead of the normally firm feel of a brake pedal.

How do you fix brake pedal goes to floor when engine running?

When the engine is running and your brake pedal is pressed to the floor, this is an indication of a serious problem that must be addressed. However, it’s easy to spot and diagnose. This problem does not involve a lot of parts of the brake system. Begin troubleshooting these issues as soon as possible:

Check brake lines and brake calipers

When the engine is running, and the brake pedal is pushed to the floor, the first thing that springs to mind for most people is a brake fluid leak. The pressure in the brake system leaks out through any of the brakes’ outflows. You must verify your brake fluid level first. If it is full capacity, there is no leak.

Check the brake fluid level, replace the leaking component, and refill the brake fluid. If there is a leak, check the four wheels for any oil residue on one of them. Then inspect the brake fluid line to see if there is a hole or anything wrong with it. Finally, replace the faulty part and refit everything appropriately.

Check brake master cylinder

The brake master cylinder is the next item to check since it contains some seals that must be closed with oil. As we previously said, these seals may deteriorate with time as a result of the vehicle’s age, resulting in brake fluid leaking out. In this instance, a new master cylinder should be installed.

Install a new one, not a re-built one. A worn cylinder won’t last long. It may function well at first, but it will deteriorate with time.


Why do I lose brake pressure when I start my car?

If you have a leak in any of the brake components, you might lose brake pressure after starting your car. If the brake pedal goes all of the way to the floor yet no leaks are found, it’s possible that there is a vacuum leak in the brake booster.

How do I know if my brake booster or master cylinder are bad?

There are several methods for detecting a faulty master cylinder or brake booster. You can tell that the brakes pedal sinks or feels spongey, usually indicating that there is a leak in the master cylinder. The brake pedal might be difficult to push, or the engine might stall while braking and stop working altogether. All of these indicate an issue with your brake booster or master cylinder.

Why does my brake pedal go to the floor after bleeding?

When bleeding the air out of the brake fluid, you must apply firm pressure to the brakes in order to restore pressure back to the brake lines.

What causes a hard brake pedal?

When the brake pedal is hard, it usually implies that the brake booster needs to be replaced. The brake master cylinder receives boosted pressure from the vacuum air in the engine by way of a vacuum booster.

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