The brake pedal is a piece of metal that every driver is very familiar with.
It’s what you press down on when you want to slow down.
You typically don’t think about your brake pedal – until it doesn’t work!
Then, you likely can’t stop thinking about it and need to get it checked by a mechanic immediately.
So what’s making your brake pedal act strangely?
And more importantly, what can you do about it?
In this article, we’ll explore how brake pedals work, what can go wrong with them, and the best way to get your brake pedal fixed.
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The brake pedal is the part of the car that initiates the entire brake system in a vehicle. In automatic cars, it’s the pedal on the left side, and in manual cars, it’s the middle pedal.
When you press down on it, all the components of your braking system swing into action.
A person can typically apply around 70 lbs of force with their foot on the brake pedal. But to stop a vehicle, your disc brakes usually need roughly 800-1,200 psi of force at the calipers.
That 70lbs of force you apply on the brake pedal is amplified by different parts of the brake system — where ‘pedal ratio’ is one of the key amplification elements.
What’s that?
The pedal ratio defines how the force applied to the brake pedal is multiplied and transferred to the brake master cylinder.
It involves some physics that includes the brake pedal length, its pivot point, and the pushrod position of the master cylinder, but we’ll spare you the details.
After you press down on the pedal, the master cylinder transforms that force into hydraulic pressure in the brake lines.
This hydraulic pressure in the brake lines engages the piston at the:
The friction material on the brake pads (at the brake caliper) or brake shoes (on the wheel cylinder) then stop the wheels from moving.
What about the parking brake? Does it work the same way?
No. The parking brake system functions separately from the brake pedal’s hydraulics. It’s a safeguard to keep the vehicle at a standstill when parked and isn’t used for regular braking when the vehicle is in motion.
You now know how brake pedals work.
But what’s going on if your brake pedal isn’t functioning normally?
You’ll rarely detect a physical problem on the brake pedal itself, but you can spot a brake issue from how the pedal feels when pressed.
Here’s what you should look out for:
A soft brake pedal results in a mushy or spongy feeling, with minimal resistance when you depress it. You might even have a low brake pedal where it drops to the floor of your vehicle and doesn’t spring back correctly.
If you’re on the road when this happens, try pumping the brake pedal a few times to see if the pressure will build up in the brake lines, so that you can stop safely as soon as possible.
If you notice this happening before you even leave your driveway, don’t drive and call your mechanic instead.
Here are four of the most common culprits behind a soft brake pedal.
Brake fluid is the conduit through which the braking pressure is applied.
The presence of air in your brake lines (that transport the fluid) will reduce the fluid’s hydraulic pressure, making the brake pedal feel soft.
Air can also make its way into a brake line during repairs, when you add brake fluid, or even during the vehicle’s general operation. Or worse, it can happen when there’s a leak in your brake system.
The lack of brake fluid in your brake system will cause your brake pedal to drop with minimal resistance. A low brake fluid level can also trip the brake warning lights on your dashboard.
The most likely cause of this is a brake fluid leak, which can occur at many points in the brake system.
A leak can spring at the brake hose, brake line, or any piston seal at the master cylinder, brake caliper, or wheel cylinder. An aged master cylinder reservoir, too, can crack and seep brake fluid.
If there’s a puddle of brake fluid under your car (which will be a clear, light yellow to brown color, depending on its age), take note of where the leak appears. Its location can help your mechanic check what component is leaking.
The brake pad or brake shoe isn’t meant to last forever.
As the pads wear down and reach the end of their life, the piston driving the caliper or wheel cylinder has to extend further to stop the wheel’s rotation. This will cause the brake fluid level to drop, and you may notice a lowered brake pedal.
The brake fluid reservoir is usually large enough to accommodate this eventuality. But brake pad wear can trigger problems in other components — like a leaking seal on a hyperextended piston.
The brake master cylinder pumps brake fluid into the brake lines. Seals within the cylinder bore that contains the master cylinder piston can also fail due to age and wear.
When this happens, brake fluid will leak, dropping pressure in the brake lines, and you’ll notice the brake pedal sinking to the floor.
Problems in the brake system can also be reflected in a hard brake pedal. This is when you find that you need extra effort to press down on the pedal.
If this happens mid-driving and your brake pedal feels locked, don’t panic and lose control. Downshift your gears to use engine braking to slow the car. Once you’re moving very slowly, apply the parking brake gently to stop in a safe spot.
The brake booster amplifies the power in a brake system that has “power brakes.” Without it, stopping distances can increase dramatically, placing you at risk of collision during emergency stops.
It works by using the engine manifold as a vacuum source to multiply the force applied on brake pedals, making braking easier.
A front booster seal failure is the most common cause of a bad brake booster. When this happens, the reduced vacuum pressure makes it harder to press the pedal, or the brakes might not even engage at all.
Additionally, a front booster seal failure can also cause the rear seal on the master cylinder to fail over time.
Age or wear are factors that drive failure in a brake booster. Additionally, boosters can go bad faster for a driver who’s in stop-and-go traffic as the brakes are engaged more often.
The vacuum hose helps deliver the vacuum to the brake booster. A problem with the vacuum hose (like a leak) can make the brake booster malfunction, translating to a hard brake pedal.
Brake fluid is a hygroscopic fluid, which means it absorbs water. Sludge will build up in the brake system over time and make it seem like the brake booster is failing.
When this happens, bring your car to the mechanic for a check and have your brake fluid replaced.
You might feel your brake pedal pulsating or vibrating from time-to-time.
Are pulsating brake pedals dangerous?
Mild pulsation is not an immediate cause for concern. However, you need to be aware that even mild pulsation can influence ABS performance on your brakes and increase braking distance during hard stops.
In extreme cases, or when wheel traction is marginal (like on slick or icy roads), pedal pulsation can cause uneven braking, making the vehicle hard to control.
Here are some typical causes of brake pedal pulsation.
A warped brake rotor is shaped like a potato chip. The high spots on the rotor will push back against each caliper piston as they revolve between the brake pads.
That push back is transmitted directly to the pedal, causing it to pulsate. If the suspension bushings are worn, the steering wheel might even shimmy.
Warped brake rotors can be caused by:
If brake pads aren’t properly bedded-in or are severely overheated, the transfer of friction material (from brake pads) to the rotor can be uneven.
This creates a rougher rotor surface that’s felt in the brake pedal. You might even see stains or dark spots on the rotor from heavier deposits that won’t wash off.
When your brake pads are worn, it can be tempting to install new brake pads and just leave them at that.
However, new brake pads (especially if they’re different materials from the old ones) won’t grip the old rotor as well and may cause the brake pedal to pulsate.
Resurfacing old rotors, or replacing them with new ones, gives the new brake pads a fresh surface for friction material to thinly coat during the bedding-in process.
There are other reasons for brake pedals to pulsate — like warped hubs, wear on the wheel bearings, or stiff CV-joints that cause the stub axle to wobble.
While any of these things alone could produce such a minimal runout that it can’t be measured, when combined, it can be felt in the brake pedal.
Clearly, there are tons of reasons for your brake pedal to act abnormally.
So, how do you explain it to your mechanic?
When the brake pedal behaves strangely, letting your mechanic know the exact symptoms can help them identify the source of the brake problem.
Here are some questions to ask yourself which will help you and your mechanic pinpoint the right issue:
As always, the best prevention for brake problems is to get regular brake service to ensure everything is working fine.
While it’s always a good idea to get your car serviced regularly to identify and repair brake pedal issues, make sure the mechanics you use are:
Additionally, you may want to consider opting for a mobile mechanic who can come over and fix your brake problems in your driveway – instead of driving to a repair shop.
The expert technicians at RepairSmith are a great option for this.
RepairSmith is the most convenient mobile car maintenance and repair solution.
Here are the benefits of having RepairSmith as your vehicle repair solution:
To get an accurate estimate of what your brake problem will cost, just fill this online form.
Your brake pedal plays a vital role in keeping you and your car safe.
So, the next time you get behind the wheel, pay attention to how your brake pedal feels, as changes in how it feels and behaves can indicate different kinds of problems with your brakes.
But, don’t worry.
If you do have a brake issue, RepairSmith is just a few clicks away.
All you need to do is book an appointment online, and an ASE-certified technician will come fix everything right in your driveway!
