Ask Car Mechanic

Ask Car Mechanic

How To Fix It

Why Brake Pedal Sinks to the Floor?

//

Why Brake Pedal Sinks to the Floor?

Driving your car is a necessity for everyday life, meaning that it must be in working order as much as possible. When it breaks down, it gives you signs to let you know something is wrong. What happens when one of those signs is your brake pedals sinking to the floor? 

When your brake pedal sinks to the floor, there’s a severe problem with the braking system that is causing it to fail, making the car extremely dangerous to drive. Brake system failure can be caused by a brake fluid leak, air in the brake lines, a bad booster, or a master cylinder

In this article, I’ll explain the possible reasons for your brake pedal failure, how to check for them, and how you can prevent more severe and expensive repairs from being necessary for your car down the road. 

Reasons Your Brake Pedal Could Be Sinking

If your brake system is functioning correctly, the pedal should never go down to the floor. If it does, here are the primary reasons it could be happening: 

Brake Fluid Leak

Your car’s braking system is dependent on special fluid to work correctly. When you press on the pedal, it activates the piston in the brake cylinder and puts pressure on the brake lines to move the fluid into the brake caliper, which causes the brake pads to squeeze the rotors attached to the wheels and stop the car with friction. 

A leak in the brake lines will drop the pressure significantly and cause the pedal to sink to the floor because there’s not enough pressure to activate the piston in the brake cylinder. 

Read: Causes of Intermittent Hard Brake Pedal

Bad Master Cylinder

The master cylinder in the braking system is connected to the brake pedal by a pushrod and generates hydraulic pressure to engage brakes and move fluid to the wheels. The cylinder must be sealed to push brake fluid to the calipers to maintain pressure and power. 

If the seal that keeps the brake fluid inside is broken or worn down, an internal leak is caused that will create a spongy feeling under your leg. 

Air in Brake Lines

Suppose you replace the master cylinder in your car’s braking system. In that case, it can result in air getting into the brake lines, which affects the circulation of brake fluid within the lines and can create a spongy feeling in the brake pedal itself, causing damage to the brake lines as well. 

Read: Brake Pad and Rotor Replacement Cost

Bad Brake Boosters

Power boosters attached between the master cylinder and the brake pedal aid the braking system when you apply pressure to the brake pedal, reducing the force needed to stop your vehicle. 

If the brake booster is faulty, you will need more force to stop the car entirely, and it will take longer to do so because you don’t have enough power to stop the vehicle quickly. 

Brake Fading

Brake fading is another possible cause of braking system failure. This occurs when your car’s stopping power is reduced because the braking system is taking on more heat than it was designed to handle. 

Suppose your brake pedal goes to the floor after heavy braking. Your brake fluid might be boiling, or your brake pads might be scorching past the point of regular operation or design. Generally speaking, it is only an issue after repeated heavy braking or driving on hills. 

Read: Brake Fluid Change Cost

How To Check for Brake System Issues?

The silver lining about brake system issues is they are not usually difficult to diagnose, and you can take proactive action to see what needs to be fixed when things go wrong. 

Check Brake Lines and Calipers

You should first check for any brake fluid leaks by checking the fluid level in your car and then examining the brake lines from all four wheels on your vehicle. If the brake lines are dry, there is no leak to worry about.

However, if one of them is leaking, you will have to remove the wheel and find the source of the leak, which is typically a leaky caliper or wheel cylinder seal. 

Check the Master Cylinder

If the problem is not a brake fluid leak, check the master cylinder for any broken or worn-out seals that could cause leaks. If you find a leak in the master cylinder, do not attempt to drive the car unless you can fix the issue yourself. If you cannot, have your vehicle towed immediately to an auto shop for repairs. 

If you need to replace the master cylinder completely, replace it with a brand new unit instead of risking replacement with a rebuilt unit. Rebuilt master cylinders do not tend to last and may also not work in the first place. 

Read: Why Your Brakes Are Grinding When Driving

Check Brake Rotors 

Brake rotors are right behind your car’s wheels and generally can be seen without removing them. When examining the rotors, look for several physical indications of trouble with your braking systems, such as fluid leaks around the wheel itself, gouges in the rotors, or uneven brake pad material located along the surface of the rotor.

How To Fix Brake Issues Yourself?

You can not solve every problem with your car’s braking system without consulting a qualified mechanic. Still, there are a few maintenance methods you can use yourself if you are having issues with your brake pedal singing to the floor: 

1. Bleed Your Brakes

If your braking system has air in the lines affecting cylinder pressure, you can manually pump new fluid through the brake lines to push out any air affecting the system. You can do this using an external hand pump, or you can do it with two people using the brake pedal itself.

Each of the car’s four brakes bleed individually using a bleeder screw located on each brake caliper or wheel cylinder. 

2. Replace the Brake Pads

Brake pad replacement varies with each vehicle, but generally speaking, they should be replaced every 25,000 to 65,000 miles (40233.6 – 104607.36 km), while your brake rotors can last between 30,000 to 70,000 miles (48280.32 – 112654.08 km). 

If you have been doing a lot of heavy braking recently or have experienced brake fade, changing your brake pads as soon as possible might be your best course of action. You may also want to look into brake pads designed to handle higher temperatures. 

How Do I Know When To Change My Brake Pads?

There are six main signs that your brake pads need to be changed immediately: 

  • Brake indicator light on dashboard
  • Brake pads thinning
  • Squeaking or squealing sounds
  • Grinding sounds
  • Vibration while braking
  • Longer stopping distance

Let’s take a closer look at each of these signs: 

Brake Indicator Light on Dashboard

Your car most likely is equipped with brake warning lights for your Anti Lock Braking System (ABS) and your general brake system warning light. The light also appears on your dashboard when your car’s parking brake is engaged, but it doesn’t always occur when there is an issue with its braking system. 

If you see the warning light come on without the parking brake engaged, take your car to the shop immediately to diagnose it by a brake specialist. 

Brake Pads Thinning

You can visually inspect your brake pads for wear by looking in between the spokes of your wheels and checking the thickness of the pads. If the pads are less than a quarter of an inch thick, it is likely time to replace them. 

Squeaking or Squealing Sounds

Excessively worn down pads that need replacing soon will start making a squeaking or squealing noise as the first indicator every time you engage the brakes. Replace the pads not long after you start hearing this noise, or it will lead to potentially more damaging repair costs. 

Grinding Sounds

After your worn-down pads stop squeaking or squealing, they will start to grind into the rotors and cause more damage to the braking system as a whole. The noise could also be a metal wear indicator that warns you to replace the pads.

Either way, if you continue to let the pads grind, it will damage the rotors and potentially freeze the calipers. 

Read: How To Temporary Fix Grinding Brakes?

Vibration While Braking

If your car vibrates while braking, your brake rotors could be warped, and the brake pads could also have uneven wear. Driving with uneven wear on your brake pads can be dangerous. So, if you are experiencing any vibration while driving, take your car to a brake specialist right away.

Longer Stopping Distance

If it takes you longer than usual to stop your car when applying the brakes, your braking system could be suffering a loss of performance. This performance loss could be a sign of any of the issues mentioned above and should be addressed by a mechanic immediately.  

Final Thoughts

If your break pedal is sinking to the floor, you should take your car to a mechanic immediately so the issue can be diagnosed. The best way to avoid serious braking system issues is to keep up on the maintenance of your pads and rotors and check the system for leaks and other problems that could affect it over time. 

If your car’s braking system does fail at any point, take it to a mechanic or brake specialist immediately before trying to drive it anywhere else on your own.

Leave a Comment