Every time you press the brake pedal on your BMW, hydraulic fluid is pushed through the brake lines, forcing the brake pads to squeeze down on the brake discs, slowing your car down. When it’s time to replace the pads and/or rotors, it’s a good idea to change your brake fluid as well. However, this means bleeding the brakes
Contrary to popular belief, you can do this yourself with some basic tools. This article will include a step-by-step guide on how to bleed brakes by yourself and why and when you should do so.
When Should You Bleed Your Brakes and Why?
If your car’s brake pedal seems a little spongier than usual, or if you’re not getting adequate brake pressure, it’s a sign that you might have to bleed the brakes. It’s also a good idea to replace the brake fluid every two years or so, even if you’re not experiencing a drastic drop in braking performance. The fluid will collect water over time because it is hygroscopic. In other words, it naturally attracts water.
That being said, you’ll need to bleed the brakes any time you replace brake pads, and brake lines, rebuild a brake caliper, or do anything that requires you to open an otherwise closed hydraulic system.
Doing a Brake Fluid Flush
The process of flushing your brakes is similar to bleeding the brakes. A brake fluid flush involves removing the brake fluid entirely and replacing it with fresh brake fluid. On the other hand, brake bleeding entails removing just enough fluid to eliminate any air bubbles trapped in the system.
As mentioned above, you should perform a brake fluid flush every two years due to potential water contamination. A hygroscopic fluid tends to absorb water from the surroundings, and this can cause it to evaporate under the high temperatures generated by braking. This, in turn, results in air bubbles in the brake fluid and air pockets, both of which will affect the braking efficiency of your BMW.
Replacing Calipers, Brake Lines/Hoses, and Other Components
You should also bleed the brakes every time you replace the brake calipers, master cylinder, or any brake lines and hoses. While replacing the calipers is a closed system job (the hydraulic fluid is not exposed to the atmosphere), it’s still a good idea to bleed the brakes to ensure optimal performance.
Meanwhile, replacing the brake lines or master cylinder will definitely warrant a brake fluid bleed or flush since they expose the fluid to air.
What Type of Brake Fluid Should You Use?
When replacing the brake fluid on your BMW, you must stick to the DOT (Department of Transportation) rating recommended by the manufacturer. You can find this info in the owner’s manual or the brake fluid master cylinder.
While DOT ratings range from DOT 1 to DOT 5.1, most modern-day cars, including your Bimmer, will likely use a DOT 4 or DOT 5.1-rated fluid. Typically, a fluid with a higher DOT rating has a high boiling point, which translates to higher performance.
Using a brake fluid with a DOT rating that isn’t recommended by the manufacturer can cause a severe drop in performance. With the DOT rating, the viscosity of the fluid changes, too, so using a higher-spec fluid on your car may not always be the best course of action.
Performance Brake Fluids
Performance brake fluids, like the Motul RBF660, typically have significantly higher dry and wet boiling temperatures than regular brake fluids. For the uninitiated, the dry boiling point of a brake fluid refers to the boiling temperature of a fresh fluid in a sealed container. Meanwhile, the wet boiling point is the temperature at which brake fluid will boil when it contains 3.7 percent water by volume. These figures are used across the industry to establish the efficiency of brake fluid. Simply put, the higher the figure, the better.
It’s worth noting that performance brake fluid on a daily driver might be overkill, and what the manufacturer recommends should do just fine. However, if you take your car to the track and have the hardware — calipers, brake lines, master cylinder — that can make use of performance brake fluid, you can consider making the switch.
How to Bleed Brakes by Yourself?
If you’re by yourself or want to avoid the labor charges involved with hiring the services of a professional, all you need is some basic tools to bleed the brakes on your BMW yourself. While there are many ways to do a brake bleed, some are notably more efficient and straightforward than others.
Here’s a step-by-step guide on how to bleed brakes by yourself:
Tools and Accessories
There are two ways you can go about bleeding the brake fluid in your car by yourself. The first is a DIY approach requiring a plastic bottle and some rubber or silicone tubing, while the second is a more conventional method using a dedicated brake bleeding kit. If you’re looking to save a little money, the latter is a cost-effective yet efficient method of removing any air bubbles trapped in the brake lines. If not, you should get a brake bleeder kit.
Make the Bleeder Bottle
To make the bleeder bottle, take an old plastic bottle and make a hole in the cap that’s wide enough to fit a piece of tubing. You should use a tube that sits snugly over the bleeder screws on your car. Typically, a 3/16-inch line should work. Use a wire tie or adhesive to ensure the tube is secured through the bottle cap. Then, take fresh brake fluid and fill the bottle just enough that the tube is submerged in fluid. That’s it —- the bleeder bottle is ready.
Prep the Car
You will need to remove the wheels to access the brake bleeder screws, so raise the car off the ground with jack stands or a lift. Then, top off the brake master cylinder with fresh brake fluid. Ensure that you don’t let any dirt enter the reservoir when you open the cap.
When you’re bleeding the brake fluid, it’s important that you follow the pattern recommended by BMW for your particular model.
Start the Bleeding Process
To start the bleeding process, attach the hose from the bottle to the bleeder screw of the wheel you’re working on and loosen the screw slightly. Once that’s done, get into the car and depress the brake pedal repeatedly to force the brake fluid into the bottle. Continue to do this until you see no more air bubbles in the piping. Usually, 5-6 pumps do the job.
If you’re using a brake bleeder kit, the process is similar. Just attach the reservoir included in the kit to the bleeder screw and carry out the same process. If your kit consists of a vacuum pump, you can use that to draw the brake fluid out.
Once all the air in the system has been removed, you can tighten the bleeder screw and remove the piping.
Refill Master Cylinder
Remember to refill the master cylinder every time you bleed a caliper. If it’s too low, it can cause air to enter the system, forcing you to restart the process from scratch.
Follow the above steps for each wheel, topping up the master cylinder as you’re done.
Go for a Test Drive
Once you’ve got all the air out of the system and refilled the master cylinder, take the car for a short drive. It’s a good idea to pump the brakes a few times before you start to build pressure and heat in the system. We also recommend driving exceptionally slowly and checking for brake feedback before leaving your driveway to eliminate the risk of an accident.
The brakes on your Bimmer should provide a good feel and feedback. If it’s still spongy, there may be a leak in the system and parts that need to be replaced. However, if you carry out the process correctly, you should not face any issues.
Get Your Brake System Supplies at Bimmers.com!
Now that you know how to bleed brakes by yourself, you can save on the costs of having it done by a service center. Having brakes that perform as they should is fundamental to your safety and the performance of your Bimmer. The braking system is subject to extreme heat; over time, the pads, calipers, and brake lines will wear out.
When it’s time to replace them, get reliable parts from trusted brands at Bimmers.com. With a portfolio that includes everything from brake master cylinders to ABS assemblies, Bimmers.com has one of the largest inventories of BMW parts in North America. Simply search the site with the year and model of your car to see all the compatible parts in stock.
