If there is one part of your car that you always want to make sure works properly, it is your brakes.
However, since today’s cars are so high-tech, you may be wondering if your vehicle’s brakes will work when the engine is not running.
Most modern car brakes will still work when the engine is turned off, but not nearly as efficiently. Without the power to the engine, the automatic braking systems that assist with applying pressure to engage the brakes will not turn on, making stopping much more difficult.
Since the answer to your question is somewhat mixed, here’s what you need to know!
What Happens if You Press the Brakes When the Car is Off?
When you press the brakes on your car when the engine is turned off, the good news is that you will still have brakes that work. However, the downside is that they probably won’t work as well as they do when the engine is running!
When your car is being operated under normal driving conditions, your brakes receive assistance from your car’s engine through what is known as a vacuum booster.
Powered by your car’s engine, this booster is what helps create a large amount of pressure your brakes rely on when you are driving.
As a result, you probably notice you don’t need to apply much pressure to your brakes to make them work.
Once your car’s engine is turned off, everything changes.
For starters, the circuit pressure within your car’s braking system drops drastically, since there is no longer any vacuum assistance coming from the engine.
When this occurs, you’ll notice your brakes become much harder to press down.
Yet despite this, they will still work and allow you to stop your car.
To get a good understanding of this, press on your brakes when the car is idling.
When you do, pay attention to how your engine will begin to run much faster.
This is due to the engine trying to compensate for the power needed to make the brakes work as they should.
In other words, the engine needs to pull in additional air so that it can create a vacuum needed to give the brakes their boost.
Why Brakes Don’t Work with the Car Off
As you have probably figured out by now, your brakes don’t work as well with the car off because there is no automatic braking system there to help them have additional power.
When discussing your car’s automatic braking system, you should realize that its goal is to apply pressure to each of your car’s individual brake calipers, which is what lets you bring your car to a stop without sliding all over the place.
Without your car’s engine running, the automatic braking system is unable to rely on its hydraulics.
When you apply the brakes on your car, it is the hydraulic system that allows the greatest amount of force to quickly shift to your car’s front wheels and brakes.
If you’ve heard of disc and drum brakes, you’ll be glad to learn that the disc brakes, which are usually the more efficient, are used on your front wheels, while drum brakes tend to be on the rear wheels of your car.
If you’ve taken a look under your hood and know even the slightest thing about brakes, you know your brake’s hydraulic system can’t do anything at all without brake fluid.
If you have a current model car, it is likely equipped with what are called master cylinders and slave cylinders.
When you press down on your brake pedal, brake fluid is pushed through pipes thanks to a piston in the master cylinder.
Once the fluid reaches the slave cylinder, this is what makes your car come to a stop.
In case you’re worried about what would happen if your car’s master cylinder failed and that you might not be able to stop your vehicle, put those worries aside.
Most newer cars today are equipped with a tandem system, which means if one fails there is a backup ready to step in and help.
To put this in perspective, keep in mind that while the master cylinder pistons may have to travel a distance of up to six inches so that the slave cylinder can be filled with brake fluid, the slave cylinder itself needs to only move less than one inch to apply pressure to your car’s brakes.
What if I Notice Fluid Leaking?
If you notice brake fluid is leaking from your car, it is important you take it to a mechanic as soon as you can.
The less brake fluid your car has, the less pressure will be applied to your brakes.
When your car has no brake fluid, chances are a slight tap of your brake pedal will send it all the way to the floor.
While you may still have minimal braking ability, you don’t want to risk getting into an accident.
When a fluid leak is visible, this usually means either the master cylinder is getting ready to fail or has in fact already expired.
What is an ABS?
Unless you are driving a really, really old car from decades ago, chances are your car is equipped with an anti-lock braking system, commonly known as ABS.
Using a combination of sensors and valves, the ABS keeps your car from going into an uncontrolled slide.
Yet for the ABS to work as it should, it all comes back to the brake fluid.
Also, if your car’s engine is off, you’ll still notice your ABS brakes will feel harder to push down, which will be because they are not getting the aforementioned boost from the engine.
While an ABS will often have drivers saying their cars feel as if they are stuttering and stumbling to a halt, this is considered normal for these systems.
Should you notice anything that raises concerns, let a mechanic examine the ABS.
Now that you know your car’s brakes will still work even if the engine is off or you have a fluid leak, you can rest a bit easier.
However, since your brakes are the only thing standing between you and a serious accident, give them the extra care and attention they need to work properly.
If you found this article helpful, make sure to take a look at some of my other brake-related articles below!