Do you need to have your car on or off when bleeding brakes? This is a question that many car owners face when it comes to maintaining their vehicles, and the answer may not be as straightforward as you might think.
In this article, I will discuss the various factors that can influence the process of bleeding brakes based on my experience and provide some general guidelines to help you decide whether or not it’s a good idea to turn off your car when bleeding them.
Brake Bleeding Explained
Before we dive into the question of whether to turn the car on or off when bleeding brakes, it is important to understand exactly what this process involves.
Bleeding brakes refer to the removal of air from the brake system.
Air can enter the brake system through various means, such as a leak in the brake line, a punctured brake hose, or simply through normal wear and tear.
When air is present in the brake system, it can cause the brake pedal to feel spongy or unresponsive, which can compromise the safety and performance of your vehicle.
To bleed the brakes, you will need to release the brake fluid from the bleeder valve on each brake caliper or wheel cylinder.
This is typically done by using a wrench to loosen the valve and a container to catch the brake fluid as it is released.
As the brake fluid is released, air bubbles will be expelled from the system. Once the fluid is released from the valve is free of air bubbles, the valve can be tightened and the process can be repeated on the next brake.
Should You Bleed Brakes with the Car On or Off?
Now that you have a basic understanding of what it means to bleed brakes, let’s explore the question of whether to turn the car on or off when performing this task. It is generally recommended to bleed the brakes with the car off.
There are several reasons why bleeding brakes with the car off is the preferred method.
First and foremost, when the car is turned off, there is no pressure in the brake system. This makes it easier to release and replace the brake fluid, as there is no resistance from the pressurized system.
Additionally, bleeding brakes with the car off allow you to work at your own pace and take breaks as needed, without the risk of the car starting or moving unexpectedly.
On the other hand, bleeding brakes with the car on can produce high pressure in the brake system, which can make the process more difficult and potentially damaging to the brake system.
Pressing the brake pedal in a running car can produce around 100 psi of pressure, which is enough to stop a vehicle from traveling at high speeds.
This high pressure can make it difficult to release and replace the brake fluid, and it can also increase the risk of damaging the brake system or the bleeder valve.
What Factors Can Affect the Process of Bleeding Brakes?
While it is generally recommended to bleed brakes with the car off, there are some factors that can influence the process and determine whether it is best to turn the car on or off. Here are a few factors to consider:
- Type, model, and year of the car: The specific type, model, and year of your vehicle can affect whether it is best to bleed the brakes with the car on or off. Some older models may require the vehicle to be turned on in order to properly bleed the brakes, while newer models may have a different method for bleeding the brakes. some cars require you to have a scanner (obd2) before you bleed the brakes and some don’t. It is always essential to consult the owner’s manual or a mechanic for proper instructions on how to bleed brakes for your specific vehicle.
- Type of brake system: The type of brake system can also influence the process of bleeding brakes. For
- example, some vehicles have a hydraulic brake system, while others have an electronic brake system. The method for bleeding brakes can vary depending on the type of brake system, so it is important to know which system your car has and follow the proper instructions for bleeding it.
- Location of the bleeder valve: The location of the bleeder valve can also affect the process of bleeding brakes. If the bleeder valve is easily accessible, such as on the caliper or wheel cylinder, it may be more convenient to bleed the brakes with the car off. On the other hand, if the bleeder valve is located in a hard-to-reach spot, it may be easier to bleed the brakes with the car on so that you can access the valve more easily.
- Personal preference: Ultimately, the decision of whether to turn the car on or off when bleeding brakes may come down to personal preference. Some people may prefer to work with the car off because it is easier and safer, while others may prefer to work with the car on because it allows them to access certain parts of the brake system more easily.
In conclusion, it is generally recommended to bleed brakes with the car off in order to remove air from the brake system more easily and safely.
However, the specific type, model, and year of your car, the type of brake system, the location of the bleeder valve, and personal preference can all influence the process of bleeding brakes and determine whether it is best to turn the car on or off.
Always consult the owner’s manual or a mechanic for proper instructions on how to bleed brakes for your specific vehicle.
Robert Anderson is a world class motorhead who rebuilt his first carb at age 10, his first engine at age 15, and completed his first full hotrod build when he was just 18! Previously, he has ran a part warehouse, delivered pizzas, and managed the service department for a $20 million/year revenue dealership. Robert knows cars like few others and he is passionate about sharing his knowledge.