Replacing the flexible brake hose on any Mercedes-Benz vehicle is a simple procedure.
Whether you are changing all four brake lines or only just one, read this article and watch the video at the end to learn a few important tips.
What you will need
- Mercedes Brake Hose
- DOT4+ Brake Fluid
- Flare Nut Wrench
- 10mm, 11mm, 14mm wrench
- Flat Head Screwdriver
- Penetrating Oil
- Work Gloves
How to change Mercedes Brake Hose
Before you get started there are a few important points that you need to keep in mind.
When you disconnect the brake hose you are going to lose brake fluid. Only use the recommended fluid for your Mercedes-Benz which in most cases is DOT4+ Mercedes Brake Fluid. It is different than DOT4 brake fluid and based on our research it is not compatible with DOT 5 and 3. The brake fluid can be purchased online or from any Mercedes-Benz dealer. At the dealer 1 quart costs about $25 USD.
- If your vehicle has SBC brakes (often found in 2003-2006 E and CLS class), you will need to disconnect or disable the system before you change the brake line.
- Pay close attention to the routing of the existing brake hose. If you route the new brake hose incorrectly it can stretch and burst when making left and right turns. Take a few pictures of the old brake line. If you get stuck or are wondering how the brake line was routed, you can always review the pictures.
- Jack up your Mercedes-Benz and remote the wheel where the bad brake line is located. If you are changing all four, start with the right rear brake hose.
- Locate the brake line that needs to be replaced. In all Mercedes-Benz vehicles, the flexible brake line goes from the caliper to the strut and connects to the brake line near the wheel well.
- Use a wire brush to clean any dirt or debris from the caliper where the brake hose connects to it. You will be removing the hose and don't want dirt to enter the brake caliper.
- Spray penetrating oil on the connections. Allow the penetrating lubricant to soak for at least five minutes. This step is a must. It is very easy for the nut to get rounded especially if there is rust at the connection.
- Place a pan under the brake line to catch the brake fluid that will leak when you disconnect the line.
- Disconnect the line where the rubber hose connects to the metal brake line. You will need to hold the rubber brake hose using a 14mm open-end wrench and rotate the 11mm nut. Use a flare nut wrench to avoid stripping the nut. It is important that you don't rotate the rubber brake line. The line has small tabs that will not allow it to rotate.
- To minimize brake fluid loos warp plastic at the tip of the metal brake line/flare. This will minimize the loss of brake fluid and give you t time to change the brake line. You can also remove the cap from the bleed valve and place it on the flare to stop the brake fluid leak.
- Use a 14mm wrench to hold the brake line and flare nut wrench to disconnect the brake hose. If you don't have a flare nut wrench use an 11mm open-end wrench, but you must be very careful because the nut can get damaged.
- Disconnect the brake line from the rotor using a 14mm open-end wrench. Turn the brake hose counterclockwise to remove it.
- Install the new brake line. First, you should connect the brake hose to the caliper.Start threading the brake line by hand into the brake caliper. The brake line should go in easily. Be cautious because it is easy for the brake hose compression fitting connection to cross-thread when screwed into the brake caliper.
- Secure the brake line to the strut and steering knuckle. Route it exactly the same way the old brake line was installed.
- Connect the flexible brake line to the metal brake line.Note the exact orientation of the U clip.When installed properly it will not allow the brake line to spin. Even though the brake line should not rotate, you must counter-hold it to prevent damage to the brake line.
- Add brake fluid.Only used the recommended Mercedes-Benz brake fluid.
For most models including C, E, S, ML, GL, R, CLS, class the most used is DOT4+ Brake Fluid. It is not the same as DOT4 Brake Fluid.
- Bleed the brake lines.Loosen up the bleed valve at the caliper that you changed the brake line. Only rotate the bleed valve about one turn.
Tip: Connect a clear tube the caliper brake line to minimize the mess and avoid brake fluid squirting out of the bleed valve.
- Start the car and press the brake pedal a few times until you see brake fluid dripping out of the bleed valve. Tighten the bleed valve. There will be brake fluid leaking at the bleed valve. There should be no air bubbles formed at the tip of the bleed valve. Close the bleed valve when you see a steady brake fluid coming out of the bleed valve.
- Add brake fluid to bring the level of the MIN and MAX level.
- Next, we need to inspect for brake fluid for leaks at the connections. You should clean the brake line connections with a clean cloth. Press the brake pedal at least ten times with the engine running.
Turn off the engine and inspect for brake fluid leaks at the connections. If any connection is leaking or bleeding brake fluid you should tighten it and reinspect for leaks.
- If your brake pedal feels soft it is recommended to bleed the brake system for air using a Brake Fluid Bleeder pump. Start at the wheel furthest from the brake fluid reservoir which in most cases is the rear passenger side wheel.
Mercedes-Benz brake hoses do not fail frequently but they do tend to become too stiff, dry rotted, cracked, or weep fluid. On older Mercedes-Benz, the fittings may start to rust and leak.
In a few cases, we have seen Mercedes brake hoses may also swell internally decreasing the inner diameter of the line and thus reducing the brake fluid flow. In turn, this can cause the brake pads to grab the rotor because the piston in the brake caliper can't open quick enough.
This can cause your brake pads to wear a lot sooner. If you are experiencing any of these symptoms you may want to replace your Mercedes brake line for your safety.
At the dealer, you will get quoted anywhere from $200 to $450 to change one brake hose. Changing the brake hose yourself is possible and not as hard as you think.
A new Mercedes-Benz brake hose can be purchased online for any model and they typically run in the $25-$50 price range.
- Avoid losing all of the brake fluid from the brake fluid reservoir as this may introduce air into the other brake lines and will require that you bleed all the lines.
- High temperatures can cause your Mercedes Benz brake lines to fail prematurely.
- If your brake lines haven't been changed in over 10 years, we would recommend that you change them even if they don't show any wear signs.
- Brake hoses can deteriorate in the inside and you will not be able to visually inspect. If that is the case the brake pads may grab, rotors get too hot. This may be the case if you changing brake pads more frequently than you should.
- Poor braking on one side can cause your Mercedes-Benz to pull to one side when braking.