A person in a brown leather shoe is pressing the pedal of a car that won't start and has a stiff brake

3 Reasons for a Stiff Brake Pedal and Car That Won’t Start


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Help! My car isn’t starting and the brake pedal is stiff – why?! First of all, if your brake is stiff and car won’t start then you’ve already pieced together two clues.

In many cars, especially new and automatic cars, there’s a connection between the brake being pressed down and your car starting. In other words, the brake is actually part of the circuit for your vehicle’s ignition.

But since we’re talking about cars with many moving parts, there are more than just these two clues. In this blog post, we’ll explore the various potential causes behind this peculiar issue.

A woman wearing a hat is standing next to a vintage car with a stiff brake that appears to prevent the car from starting

Can brakes cause a car not to start?

Yes, as we mentioned, the braking system is actually an integral part of the ignition system for some cars. For that reason, in an automatic car, you need to press your brake in before your car can start. This is to prevent accidental start if say your pet dog excitedly presses the ‘start’ button.

When your brake is stiff and your car won’t start, this also serves another safety net. A stiff break might indicate a fault in the braking system. If that’s the case you’re better off with your car not starting.

Note that your brake is always going to be a little stiffer while your car is switched off, so we’re not talking about that type of minimal stiffness. In a healthy car with a fully functioning braking system, once the car is up and running, your brake booster softens the amount of pressure you need to brake. More on that a little further down.

A person trying to start a car with a stiff brake.

What does it mean when your brake pedal is hard and the car won’t start?

Most of us have experienced that dreaded moment. You turn the ignition key and instead of hearing that gorgeous roar of the engine, are met with silence. (We’re talking about petrol cars here. Those who’ve made the leap to driving one of the many different electric cars will always have be met with silent-as-lamb engines).

While there could be various reasons behind a car’s failure to start, one often-overlooked culprit is a stiff or hard brake pedal. Here are four reasons why your brake is hard and car won’t start.

1. Car won’t start because of brake booster failure

One of the main reasons behind a stiff brake pedal is a malfunctioning brake booster. The brake booster is responsible for assisting with the braking effort.

Without it, you’d need to be superman to get any braking done. Thankfully, the brake booster uses the vacuum pressure from the engine so you don’t have to add as much pressure to hit the brakes.

But, if the brake booster fails then it creates a vacuum leak, resulting in a stiff brake pedal. But what does this have to do with starting your car?

A brand new brake booster ready to be installed in car

This safety feature means your car won’t start (to protect you)

Most modern vehicles come equipped with a safety feature called a brake interlock system (get more of a low down on car safety features). This safety system stops you (or your child) from accidentally starting the car unless the brake pedal is fully depressed.

If the brake pedal is stiff, it won’t depress entirely. This triggers the brake interlock system, preventing the car from starting. This is precisely what you’d want to happen if your brake booster is broken because you don’t want to be driving when you discover you can’t brake properly.

What to do

When your car isn’t starting and your brake pedal is stiff because of a faulty brake booster, this needs urgent attention. Contact your mechanic to get their advice (here’s how to choose a good mechanic).

Early signs that your brake booster is going to fail include increased braking distance (pushing your brake longer before it actually works) and warning dashboard lights. If you can get these seen to before your booster actually fails, that’s even better. Learn more about car dashboard symbols and their meanings.

A woman holding a bottle of water and car keys is frustrated as her car won't start due to the brake being stiff.

2. Brake is hard and car won’t start because of hydraulic issues

Hydraulic problems in the braking system can also result in a brake that’s hard and a car that won’t start. There are not one but several hydraulic braking issues to troubleshoot. Low brake fluid level, air in the brake lines, or a faulty master cylinder can all be contributing factors of a hard brake pedal.

These issues will affect hydraulic pressure needed to brake properly resulting in stiff brake pedal.

Similar to brake booster failure, hydraulic issues can indirectly impact the car’s starting mechanism. That’s because some vehicles have a brake pedal position sensor that communicates with the engine control unit, ensuring the car only starts when the brake pedal is pressed.

If the brake pedal is stiff, it might not register the required signal, leading to a no-start situation.

A person sitting in the driver's seat of a messy car with cables, water bottle and old takeaway cup

3. Mechanical obstructions could be the culprit

An overlooked but equally possible reason for a stiff brake pedal is a mechanical obstruction within the braking system. This could be an obstruction could be due to a stuck calliper which can happen in cars that rely on disc brakes (rather than drum brakes). The cause here could range from corrosion and wear and tear to random debris.

Even though it seems too simple to be true, also be sure to check that your floor mat hasn’t just folded on itself and isn’t getting in the way of your brake. When your brake is stiff and your car won’t start, it could be something as obscure as a child’s toy, a bottle of water or shoe that’s just getting in the way.

These obstructions prevent the necessary movement of the brake components, resulting in a stiff pedal.

A woman's hand on the steering wheel with the dashboard lights showing everything is working well

Safety first when you’re behind the wheel

While a stiff brake pedal might not be the most obvious reason behind your car’s failure to start, as you can see, it’s entirely possible. Issues with the brake booster, hydraulic system or mechanical obstructions can all lead to a brake that’s hard and a car that won’t start.

Remember to have your car checked in for a service according to schedule. That way you’re less likely to ever experience a brake that’s stiff or a car that won’t start.

Here are some guides to get you going and keep you safe:

Be sure to get your trusted mechanic’s input if you encounter any of the problems we’ve discussed – or signs they may be about to happen. That way, he or she can diagnose and fix the underlying issue promptly. After all, you wouldn’t want a simple brake pedal stiffness ruining your journey before it even begins!

Award winning car insurance to keep you going

Another great move when it comes to car safety is having a car insurance plan.

Your insurance can be tailored to your budget and it helps cover unexpected costs. For example, it can help pay for costs from damage to your car from hail, fires, storms, vandalism or even attempted theft, depending on your level of cover. All PD Insurance plans also include third party cover for damage to others’ cars and property.

Your insurance can also help pay for a replacement car if yours gets stolen too. Plus there’s a wide range of optional added benefits you can choose from, such as roadside assistance and hire car after incident. Choosing the cover extensions you need means you only pay for what suits your budget and driving lifestyle.

Getting a car insurance policy that’s tailored to your needs is easy. Simply click below to get a quote.

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