BMW brake hoses are made of reinforced rubber hoses that are built to withstand hydraulic pressure, bending, and heat. On older BMWs, the brake hose may start to show signs of cracking, bulking, or complete failure.
A soft brake pedal may indicate that your flexible brake lines are failing or there is air in the brake lines.
- BMW leaks brake fluid from the flex brake line
- Low brake fluid level on the reservoir
- Brake warning light stays ON
- No brakes on one side of the brake line
- Fluid brake leak when parked
- Poor braking performance
- Brakes feel soft when pressing the BMW brake pedal.
What you will need
- Jack up the car and remove the wheel where you need to replace the brake line.
- Spray penetrating fluid on the brake line connection and bolt that secures the brake line to the caliper.
- Open the hood and locate the brake fluid reservoir. On some BMW models, the brake fluid reservoir is located below the cabin microfilter. Remove the plastic housing to access the brake fluid reservoir. Remove the cap from the brake fluid reservoir. Remove filter using needle-nose pliers. Pump the brake fluid out of the brake reservoir. Remove as much brake fluid as you can.
- Disconnect flex brake hose where it connects to the brake line. Use an 11mm open-end wrench to loosen the union bolt where the flexible brake hose connects to the metal brake line.
- Unscrew the BMW brake line from the caliper. Use a 14mm wrench to unscrew the brake line from your BMW brake caliper.
- Install the new BMW brake hose. Screw the new BMW brake line into the brake caliper. Torque the brake line that mounts on the brake caliper to approximately 20Nm or as recommended by the manufacturer. Secure the brake line on the strut brackets where the old brake line was secured.
- Connect the flex brake line to the metal brake line. Torque the union bolt to approximately 15Nm or as recommended by your BMW dealer.
- Add Brake Fluid. Fill the brake fluid reservoir with the recommended BMW brake fluid. (If you are replacing more than one brake line, replace the next BMW brake line before moving to the next step.)
- The next step is to bleed the BMW caliper and brake lines. This step requires two people. Start with the brake caliper furthest from the brake reservoir. Loosen the bleed screw on the brake caliper. Pump the brakes until brake fluid comes out of the bleed screw, then tighten the screw. Repeat the brake bleeding procedure a few times until no more air remains and bubbles are coming out of the bleed screw. Tighten the bleed screw while your friend is keeping the brake pedal pressed.
- Check the brake fluid level and add brake fluid if necessary.
- Lower the vehicle. Install the wheel on the car. Before driving off, test the brakes to ensure your brakes are working properly.
- Inspect the hydraulic brake line for leaks after a day to ensure there are no leaks at the connections.
- Start the vehicle and test the brakes at a speed not to exceed five mph.
It is recommended to inspect your BMW flex brake hoses for cracks and lines for corrosion at least once a year. A worn BMW brake hose may burst and cause a loss of braking power while driving. If any of your BMW brake lines show signs of wear, replace them as soon as possible.
Instructions on this article will help owners of 1-series, 3-series, 5-series, 6-series, 7-series, X1, X3, X5, z3, z4, and other models.
- Brake fluid can damage your car paint. Rinse it off with water if it falls on the car paint.
- It is recommended to bleed the ABS pump as well as the brake calipers. The procedure may vary depending on the model.
- Spray penetrating oil on the old hose connections the night before when possible.
- Use the 11m brake nut wrench to avoid rounding off the locking hut on the brake line.
- Test the brakes before driving away. The brake pedal should be hard when the air bleeding is completed correctly.
- Ensure your new brake hose is the same length as the old BMW brake hose.
Frequently Asked Questions
- How long is a BMW brake hose?
- BMW brake hose can range between 40 cm and 45 cm. BMW brake hose length varies by model.
- Would a damaged brake line fail my safety MOT inspection?
- Yes, in most states and countries, you will fail the safety test if your brake lines show signs of excessive wear.
- Do I need to use a thread locker on the brake hose threads?
- No. Torque the brake hose to the recommended specifications is enough.
- I stripped the locking nut; what should I do?
- Spray penetrating oil on the nut. Give it about fifteen min then use vise grip pliers to get the nut loose.
- My BMW brakes feel soft after replacing the brake hose.
- If you replaced your BMW brake line or hose and the brakes feel soft, repeat the procedure to bleed the brake system on all four wheels.
- If replacing all BMW brake hoses, which brake horse do I replace first?
- It doesn't matter which line you replace first. The important step is the bleeding procedure. Start with the wheel's furthest distance from the brake reservoir, which will be the passenger side rear.