A bleeding brake is a simple process of letting air out of a car’s brake system. For optimal performance, it is important to bleed the brakes of a car from time to time. So, do you bleed brakes with car on or off?
Bleeding the brakes with the car off or on depends on the type, model, and year of the car you drive. However, if you want to bleed the brakes at the calipers to remove air from the system, your car should be off.
Either way, you should be careful when bleeding brakes because a slight mistake could damage the brake system. We strongly advise taking the car to a professional mechanic to do the bleeding for you to avoid damaging your braking system.
What Does it Mean to Bleed Brakes?
In simple terms, to ‘bleed brakes’ means you are removing air from the brake line. Air can enter the brake system when a connector is removed to allow fluid to flow out when a new brake line is being installed, air could also be let in the brake system when there is a fluid leak somewhere and through other ways.
The process of bleeding brakes involves opening the valve in order to allow air to escape under pressure, while the air leaves some brake fluid also escapes with it.
The problem with having air in your brake system is that it doesn’t allow the brake fluid to compress as it should. It prevents force from being applied to the brake lines when pressure is applied to the pedal.
Bleeding brakes are often time done by two persons, one person on the inside pumping the brake pedal while the other opens up the valve on the wheel cylinders.
The process of removing air from the brake lines is one that should be done with care, because if it is done incorrectly, the brake may not function properly.
Do You Bleed Brakes with Car ON or Off?
Whether to have the car on or off will depend on the individual bleeding brakes. Some would prefer to have it running as it makes it much easier to pump the pedal while others prefer it off.
The decision to leave the engine on or not will depend on your type of car and its model. For a car that requires manual bleeding, the engine does not need to be on.
Modern and newer cars on the other hand will require that the ignition is on but not necessarily running because they make use of a scanner because of the ABS module and electric parking brake.
Please take your car to a professional mechanic to help you do this. With your brand, make model, and year of car, the mechanic will know what to do.
What Happens When You Bleed Brakes When the Car is ON?
What will happen if an engine is running when bleeding brakes is dependent on your car type and model.
For modern cars, nothing may happen, but for cars that require manual bleeding the person working on it may be at risk of getting injured. It is not advisable for anything to be done in a car while the engine is running for safety reasons.
What is the Best Way to Bleed Brakes?
The best way to bleed brakes are:
1. Let the Owner’s Manual be a Guide
The first step in bleeding out the brake is getting a replacement brake fluid. The best guide to the type of fluid your car should use is the owner’s manual, you should check for the type of brake fluid your car requires and at what intervals it should be replaced.
Different cars have different fluid requirements, so it is better to use what works best for your car.
2. Raise the Vehicle on a Solid Ground
The vehicle should be raised on solid ground supported by jack stands placed at jacking points. It is important to jack up the car with something solid that will prevent it from falling while you work. If you don’t have a jack stand, a cinder block can work just fine.
3. Locate the Screw on the Four Calipers
Bleeding screws on the four calipers should be loosened gently. If the screws are not coming loose, spray them with oil to lubricate them and leave them for some minutes.
Proceed to loosen them afterward and if they are still hard to loosen or snap off, you should consult the services of a professional.
4. Check the Fluid Level in the Cylinder Reservoir
Lift the car hood and check the brake master cylinder reservoir for fluid level. You will need to top up if the fluid is lower than the line marked ‘full’.
5. Start With the Brakes
Starting with one brake, fit One end of a tube over the end of a bleeder screw. Over the end of a bleeder screw, fit a clear tube and place the other end in a container. Be sure to use a long tube so it will be easy to hang the container.
6. Pump the Pedals
Signal the assistant inside the car to pump the pedal for several strokes. Your assistant should give a sign or shout when a firm pedal is achieved. That pressure should be maintained
7. Open the Bleeder Screw by a Small Amount
With pressure still maintained, have the bleeder screw opened by a small amount? The pedal will start dropping down as fluid flows through the tube, before the pedal drops completely, the assistant should inform you then you know its time to close the bleeder screw.
8. Repeat the Last Two Steps
It’s time to repeat steps six and seven, at least five times. This should be done until the fluid is free of air.
9. Observe the Motion of Fluid in the Cylinder Reservoir
When all four brakes have been bled, you should observe the motion of the fluid in the cylinder reservoir. The bleeding process should be repeated to remove air if there is a substantial fluid eruption.
10. Be Sure all Bleeder Screws are in Place
To complete the process, you have to make sure all bleeder screws are tightly screwed in place.
Advantages of Bleeding Brakes
Some benefits of bleeding brakes are:
- It prevents Further Damage to the Car: Bleeding brakes in a car when due helps to prevent further damage from happening to the car. Timely brake bleeding saves you the cost of repairs and replacing damaged parts in the car.
- Good Performance of the Brake System: Air in the brake line lessens pressure and also reduces the car’s braking performance. Another advantage of bleeding your brakes is that it helps to improve the car’s braking performance and increases fuel economy.
 Conclusion
It is important to read the owner’s manual in order to know the required brake fluid for the vehicle, using the wrong fluid could cause lots of damage to the vehicle.