Mercedes W123 Brake Hose Replacement


  1. Mercedes W123 Brake Hose Replacement, Brake Hose: crwdns2935265:01crwdnd2935265:01crwdnd2935265:01crwdne2935265:0
    • Before beginning you will need to remove the wheel(s) that are in the way of each brake hose you want to replace.

  2. Mercedes W123 Brake Hose Replacement: crwdns2935265:02crwdnd2935265:01crwdnd2935265:03crwdne2935265:0 Mercedes W123 Brake Hose Replacement: crwdns2935265:02crwdnd2935265:02crwdnd2935265:03crwdne2935265:0 Mercedes W123 Brake Hose Replacement: crwdns2935265:02crwdnd2935265:03crwdnd2935265:03crwdne2935265:0
    • Before removing the hoses, the brake fluid on that caliper should be allowed to drain.

    • This is done through the bleed screw on each caliper. The following bleed screws are shown:

    • Front caliper bleed screw

    • Rear caliper bleed screw

    • Allow the fluid to drain by loosening the screw just two or three turns until the fluid is dripping quickly. Use a 9mm box end wrench for this job.

  3. Mercedes W123 Brake Hose Replacement: crwdns2935265:03crwdnd2935265:01crwdnd2935265:03crwdne2935265:0 Mercedes W123 Brake Hose Replacement: crwdns2935265:03crwdnd2935265:02crwdnd2935265:03crwdne2935265:0 Mercedes W123 Brake Hose Replacement: crwdns2935265:03crwdnd2935265:03crwdnd2935265:03crwdne2935265:0
    • Now it's time to begin working on removing the soft rubber hoses.

    • They connect to the caliper, and then to the hard lines at a bracket on the car.

    • You can see here where it connects to the caliper on the rear driver's side. It will be similar on all four calipers.

    • This is how they connect to the two front hard lines. They are located near the top of the inside of the fender wells.

    • And this is how they connect to the rear hard lines. Soft line already disconnected in this picture. They are located just behind the fender well, accessible through an opening.

  4. Mercedes W123 Brake Hose Replacement: crwdns2935265:04crwdnd2935265:01crwdnd2935265:01crwdne2935265:0
    • It's often the case that dirt, road grime, etc. has collected within the bracket that holds the two hoses where they connect to the hard lines.

    • In order to more easily remove the hose this should be cleaned out. A small screwdriver or center punch can be used to gently push out the dirt.

  5. Mercedes W123 Brake Hose Replacement: crwdns2935265:05crwdnd2935265:01crwdnd2935265:01crwdne2935265:0
    • Dirt and grime will also often collect around the smaller upper nut, that of the hard brake line, making it difficult to place a wrench over it.

    • This can be carefully scraped away with the tip of a small chisel or a large flat blade screw driver.

    • After scraping out all the debris in steps 4 and 5, spray the connection with some brake cleaner to remove small particles. You want to avoid introducing dirt in to your brake system.

  6. Mercedes W123 Brake Hose Replacement: crwdns2935265:06crwdnd2935265:01crwdnd2935265:03crwdne2935265:0 Mercedes W123 Brake Hose Replacement: crwdns2935265:06crwdnd2935265:02crwdnd2935265:03crwdne2935265:0 Mercedes W123 Brake Hose Replacement: crwdns2935265:06crwdnd2935265:03crwdnd2935265:03crwdne2935265:0
    • Since these hose connections are exposed to the elements under the car, and up near the wheels, they often get sprayed with water, road salt, and other corrosive materials.

    • In an effort to ease the removal of these hoses each of the connection points should be sprayed thoroughly with a penetrating lubricant.

    • Note that where the soft hose connects to the hard line the threaded area is between the lower and upper pieces of the bracket. This is the place to focus the spray of the penetrating lubricant.

  7. Mercedes W123 Brake Hose Replacement: crwdns2935265:07crwdnd2935265:01crwdnd2935265:01crwdne2935265:0
    • Once the penetrating lubricant has had time to soak in to the threads you can begin removing the hose.

    • Start at the upper end of the hose where they connect to the hard lines.

    • The upper nut, on the hard line, takes an 11mm line wrench or open-end wrench.

    • The lower nut, on the soft hose, takes a 14mm open-end wrench.

    • Loosen the upper nut on the hard line until the soft rubber hose comes loose from it. The 14mm wrench on the lower nut of the soft hose is simply used to hold the soft hose in place so it does not twist as you loosen the upper hard line nut.

    • Note that due to corrosion, this connection can be very difficult to loosen. Often, the 11mm nut on the hard line rounds off. If this happens, you may need to use locking pliers to remove it. This is covered later in this guide.

  8. Mercedes W123 Brake Hose Replacement: crwdns2935265:08crwdnd2935265:01crwdnd2935265:01crwdne2935265:0
    • With the upper connection free, now loosen the connection of the soft rubber hose at the caliper. This is done with a 14mm open-end wrench.

  9. Mercedes W123 Brake Hose Replacement: crwdns2935265:09crwdnd2935265:01crwdnd2935265:03crwdne2935265:0 Mercedes W123 Brake Hose Replacement: crwdns2935265:09crwdnd2935265:02crwdnd2935265:03crwdne2935265:0 Mercedes W123 Brake Hose Replacement: crwdns2935265:09crwdnd2935265:03crwdnd2935265:03crwdne2935265:0
    • In the occasion that the upper connection of the hose, where it connects to the hard line, is corroded to the extent where the 11mm nut rounds off while attempting to remove the line you may need to clamp the 11mm rounded off nut in a pair of locking pliers in order to get enough of a hold on it to break the lower 14mm nut on the soft line free.

    • In this case you'll use the locking pliers to hold the 11mm nut while backing the soft line off of it.

    • You may find that it is difficult to remove the hose in this way as the soft hose begins to twist. You will be working against the twisting motion of the hose this way. Since you are replacing the soft hose anyway, simply cut the hose with a suitable pair of wire cutters or a utility knife.

  10. Mercedes W123 Brake Hose Replacement: crwdns2935265:010crwdnd2935265:01crwdnd2935265:01crwdne2935265:0
    • Then simply remove the now cut lower portion of the hose.

    • Please be aware that if you are forced to resort to using vice grips to hold the small upper 11mm nut on the hard line to remove the soft line you will then need to replace the hard line as well.

    • After installing the new hoses you must bleed your brake system to remove air. Never drive the car without bleeding it. See the brake bleeding guide.


To reassemble your device, follow these instructions in reverse order.


Nicolas Siemsen


38,842 crwdns2915208:0crwdne2915208:0



Master Techs crwdns2935289:0Master Techscrwdne2935289:0





I might include that cleaning (polishing) of the HARD LINE is important as the NUT has to trsvel upwards

gvonneida - crwdns2934203:0crwdne2934203:0

some brake hard lines were installed prior to the engine.

gvonneida - crwdns2934203:0crwdne2934203:0

I might add You probably never want to replace a steel brake line.

gvonneida - crwdns2934203:0crwdne2934203:0


gvonneida - crwdns2934203:0crwdne2934203:0

I have tried and tried to get the rear hoses off my 82 300sd. Rounded the top nut. Now what? Cut it and flare the steel? Never had a fitting on a car be so stuck. I warn anyone wanting to try it.

BamBam Truth - crwdns2934203:0crwdne2934203:0



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