Mercedes-Benz Diesel Glow Plug Reamer How To W116, W123, W124, W126 & W201

Mercedes-Benz Diesel Glow Plug Reamer How To W116, W123, W124, W126 & W201

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. It is recommended to ream your glow plug chambers every 30k miles. 

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)


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