It's something that's in our driver's manual when we're studying to take our tests – what do you do when you're driving, and the brake pedal suddenly sinks to the floor?
Well, over time, we forget what's on those booklets from years past, and we need a bit of a refresher. But to help you remember for next time, we'll walk you through everything you need to know and give you a thorough understanding of why it happened in the first place – just keep reading.
What To Do if Your Brake Pedal Suddenly Sinks to the Floor While Driving
If you're driving and the brake pedal suddenly sinks to the floor, you have a very serious problem. That's because this indicates a lack of pressure in the brake system, and what that translates to is a vehicle that won't stop when you depress the pedal.
When this happens, the first thing you need to do is pump the brakes as fast as you can. This is an attempt to build brake pressure. If it works, you need to get your vehicle to the side of the road and stop driving immediately.
If you're driving a vehicle with a manual transmission, you should shift to a lower gear while doing this. Some automatic vehicles will allow you to manually select your gears too – if you can, shift to a lower gear. This will help you slow down your vehicle without needing to apply the brakes.
Just because you have brake pressure after pumping the brakes doesn't mean you've fixed the problem – in fact, there's a good chance it's only going to last a few moments. However, if you can't get pressure to build, it's time to start trying to slow down your vehicle using the parking brake.
This works because while your service brakes utilize hydraulic pressure via brake fluid to stop the car, the parking brake utilizes a mechanical linkage. In layman's terms, the brake pedal uses brake fluid to apply the brakes, the parking brake uses a wire.
You don't want to fully apply the parking brake at once though, as this will cause you to spin out of control. Instead, slowly apply the brake and give your vehicle time to slow down as you do it.
Finally, if you have a push-button parking brake that you can't slowly depress, turn off the vehicle and try to get it to slow down naturally as much as possible before applying the emergency brake.
Once you stop the vehicle and get it to a safe place, you need to contact a tow truck. There's no other way to move the vehicle safely, and there's too much to troubleshoot and repair to do it on the side of the road.
Troubleshooting a Brake Pedal That Suddenly Sinks to the Floor
If you notice the problem before you hit the road, you can troubleshoot what's going on – but whatever you do, don't take your vehicle on the road until you've completely repaired the problem and bled the brakes – otherwise, you're risking an accident.
- The first thing you want to do is double-check your brake fluid levels – if the pedal falls to the floor without any pressure, there's a good chance there's a leak, which means that you should've lost some brake fluid.
- If you have lost brake fluid, you need to inspect the brake lines, calipers, master cylinder, and brake booster until you find the leak. A brake leak is by far the most common cause of a brake pedal that suddenly sinks to the floor.
- However, another potential cause in new vehicles is an electronic problem. That's because some modern vehicles don't have a direct linkage from the brake booster to the brake. Instead, they have a brake-by-wire system that uses sensors to determine how far you've depressed the pedal to give braking systems.
And while they have a backup hydraulic brake system, if both systems fail, then the pedal can depress fully to the floor while you lose braking power.
Final Thoughts
When you depress the brake pedal, you don't just expect the vehicle to stop – you need it to. That's why when a brake pedal sinks to the floor when you didn’t depress it is such a problem, you won't be able to stop when you need to!
But knowing what you're supposed to do when the brake pedal suddenly sinks to the floor is the first step in keeping yourself safe on the road in case the worst does happen. Hopefully, after reading this guide, you know exactly what you need to do – and have an understanding of what to troubleshoot for when you do get somewhere safe.
