mercedes coolant expansion tank hose replacement

Mercedes-Benz Coolant Expansion Tank Hose Replacement Guide

A defective coolant overflow line may let the expanding coolant vent out of the coolant reservoir tank, decreasing the coolant level. This guide explains replacing a Mercedes Benz GL450 small diameter coolant line that connects the engine, radiator, and expansion tank.


One of the common symptoms of a defective plastic coolant overflow line is that the coolant level is decreasing, and the engine overheats.

What you will need

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  • Mercedes-Benz Coolant Expansion Tank Hose


  • Flat-head screwdriver


  1. Park on level ground.
  2. Shift the car in park, then turn off the engine.
  3. Let the engine cool down to avoid serious injuries.
  4. Open the hood.
  5. Find the coolant overflow line, which stretches from the engine to the radiator and finally to the coolant reservoir.
  6. Use a flat-head screwdriver to pull each connector’s retaining clip.pull-clips
  7. Prepare the new coolant overflow line.
  8. To connect the coolant overflow line to the radiator connector, align the line with the notch on the radiator side, then press down on the locking clip.install-radiator-side
  9. Align the coolant line to the connector on the reservoir side, push it until it doesn’t move anymore, then push down the locking clip to lock it in place. Note: to minimize the effort in pushing the line, you may lubricate the connector seal with coolant.install-reservoir-side

Repeat the procedure for the engine side.

What does the overflow hose do?

  • An overflow hose connects to the radiator below the cap and the reservoir tank to store the coolant overflow.

We hope you find the Mercedes-Benz Coolant Expansion Tank Hose Replacement Guide helpful. Check these troubleshooting and repair guides for more help on your Mercedes-Benz.


  • Rushit Hila • ASE Certified

    Rushit Hila, an ASE-certified engineer (G1 Automotive Maintenance and Repair), brings over two decades of hands-on experience in the automotive world to his writing. With a strong educational background, including a Master of Science in Engineering and a Bachelor of Science in Engineering, he has honed his skills and expertise through years of practical work. As a respected authority in the field, Mr. Hila is dedicated to offering insightful and valuable content that resonates with both vehicle owners and mechanics.

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