Why Hyundai Sonata Won’t Start With Brake Pedal Hard As Rock – Causes and Fixes

You just noticed that your Hyundai Sonata won’t start because of a brake pedal hard as rock. What gives?

The brake pedal is something you step on while at the same time stopping the car engine. So, when you step on it, the hydraulic fluid flows in your break lines and stops the wheels. You decelerate when you press down on it.

But what if your Hyundai fails to start and the brake pedal ends up hard? There are a few reasons why this occurs and some things you can do to fix this problem, Keep reading to learn more.

hyundai sonata won't start brake pedal hard

Why Your Hyundai Sonata Won’t Start – Brake Pedal Hard

When the brake pedal is stiff and won’t respond, there are reasons behind this concerning situation:

1. Ignition Switch Problem

A common reason is that your ignition lock cylinder or ignition switch is broken and must be replaced. This happens when the key is stuck in your ignition and worse, breaks off inside. Thus, you have to get your vehicle towed to remove the entire assembly from under the dashboard to get the ignition lock cylinder out and replace it.

Once you have the component replaced, the brake pedal should work as it should. Then, it would be easy to start your vehicle without any issue.

2. Brake Fluid Dropped

Another possible reason why the brake pedal is hard is a drop in the brake fluid level. Because of wear and tear in your car, the fluid level has dropped significantly. There may have also been an accident that caused damage to the brake line or component of your hydraulic system.

If this is the problem, then you need to step hard onto the brake pedal since there is no sufficient fluid that pushes against the pistons. You will need to get the master cylinder’s brake fluid checked and refilled. Sometimes a replacement may also be required.

3. Brake Booster

An issue with your brake booster can also cause the vehicle to fail to respond no matter how hard you step on the brake pedal. This often arises in older vehicles since they don’t have a more advanced technology in their different components and systems.

Hence, you need to get your brake pedal checked to determine what is causing the problem. This way, you can have this issue remedied sooner and prevent having to apply too much pressure onto the pedal.

4. Brake Fails To Release

You may also be encountering an issue with the brake not releasing. This is why you cannot start your car and the brake pedal is hard. If you have the parking brake stuck in the on position, this will prevent your car from rolling freely. Thus, it won’t start. The best solution is to get this component inspected since there are safety hazards that may occur when you leave the parking brake on.

Additional Pointers To Keep In Mind

When you notice that there is a hard brake pedal issue – yet intermittent – then it may be due to a lack of vacuum pressure. This is why you need to get the car inspected right away. When there is poor vacuum, the diaphragms are unable to move your pushrod into the vehicle’s master cylinder. This causes the pedal to get hard.

One quick solution is by installing a vacuum canister or pump, depending on how much pressure dropped. This plumbs into your brake system with a vacuum hose from the booster to the pump. It gives more vacuum level to your system.

Another culprit behind a hard pedal issue is a valve problem. The valve is present for safety reasons but when things are not working well, then problems can arise. Since the brake fluid cannot be compressed, this causes the pedal to get stiff.

With a tripped pressure differential valve, this requires re-centering by getting the pressure equal on both of the valve’s sides.

Overall, a complete inspection of the entire brake system can help to determine underlying issues that lead to a hard brake pedal. By analyzing all of the possible causes, you will be able to pinpoint the root of the problem and address it sooner than later.

Read More: Hyundai Sonata Jerks When Slowing Down


There are many reasons why your Hyundai Sonata won’t start and has a hard brake pedal. With the help of a qualified mechanic, you can identify the cause of the problem and have these issues addressed once and for all. Then, this will save you from massive headaches and unnecessary expenses over time.

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