How To: Mercedes Diesel Glow Plug Reamer

W116, W123, W124, W126 & W201

An Overview of the Mercedes-Benz Diesel Glow Plug Reamer

In this post, we'll be taking a look at the Mercedes-Benz diesel glow plug reamer. We'll discuss what it is, what it does, and how to use it. By the end of this post, you should have a clear understanding of the glow plug reamer and how it can benefit your Mercedes-Benz diesel engine.

What is a Glow Plug Reamer?
A glow plug reamer is a tool that is used to clean the carbon deposits from the interior of the glow plugs. The reamer consists of a cylindrical body with a blade on one end. The blade is inserted into the glow plug chamber and turned clockwise to cut through the carbon deposits.

Why Use a Glow Plug Reamer?
It is recommended to use a glow plug reamer every 30,000 miles to clean the carbon deposits from the interior of the glow plugs. Common symptoms of excess carbon in the chamber would be: smoking at startup, and engine shaking with rough start. Hard starts/No Start is also a symptom of failing/failed glow plugs.

In this post, we've taken an in-depth look at the Mercedes-Benz diesel glow plug reamer. We've discussed what it is, what it does, and how to use it. By following these simple instructions, you can easily clean the carbon deposits from your Mercedes-Benz diesel engine's glow plugs—keeping your engine running smoothly for years to come. Thanks for reading!

1. Remove the 8mm Glow Plug wire harness nuts and remove the wire harness

2. Remove the Glow Plugs with a 12mm Wrench. Ratcheting Wrenches make the job easier

3. Grease the reamer tool with high temp bearing grease, ATF or gear oil/similar to catch the carbon when reaming. 

4. Screw the tool all the way to the base and remove it. Clean off the carbon with a lint free rag or towel. Re-grease the tool and repeat the process for all 4 or 5 Glow plug chambers 


  • If the glow plug is rounded off you can use vice grips. If that does not work you can use a screw extractor set. 
  • I recommend only using Bosch Glow Plugs
  • If the 8mm nut and wire spin you can use a Flat Blade screwdriver to stop it from rotating when loosening the nut. 
  • Removing the Fuel Injector Hardlines can be helpful but is not necessary to complete the job
  • All parts and Tools can be found at

*Does Not work for Loop End Style Glow Plug.  A different style reamer is needed*

Mercedes-Benz W201
Mercedes-Benz 190D 2.2 Sedan (1984-85)
Mercedes-Benz W123
Mercedes-Benz 300CD and 300D Wagon (1982-85)
Mercedes-Benz 300D Sedan (1977-81) 
Mercedes-Benz 300TD Wagon (1981-85)
Mercedes-Benz 240D Sedan (1977-83) 
Mercedes-Benz 300CD Sedan (1978-81)
Mercedes-Benz 300TD Sedan (1979-80)
Mercedes-Benz W116
Mercedes-Benz 300SD Sedan (1978-80)
Mercedes-Benz W124
Mercedes-Benz 300D and 300TD Wagon (1987)
Mercedes-Benz W126
Mercedes-Benz 300SD Sedan (1981-85)
Mercedes-Benz 300SDL Sedan (1986-87)


Youtube Video Instructions: