I did this job on my '80 300SD a few years back. That plug was the tightest thing I have ever been able to get loose on anything.

Forget about the type that goes on a 1/2 drive ratchet. You will break the socket, ratchet, or adapter before the plug comes out.

Get the regular L shaped Allen Wrench and a good stout pipe about 6 feet long, and a strong helper (friend). We did mine from underneath, with the car on a lift. Two guys pulling for all we were worth on the end of a 6 foot pipe before it finally broke loose. I thought the pipe was going to break first.

I am not kidding, those plugs are EXTREMELY difficult to remove.

Good Luck.

SteveM.

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'93 190E/D 2.5 Turbodiesel 5-speed (daily driver)
'87 190D 2.5 Turbo rustbucket - parts car
'84 Dodge Rampage diesel - Land Speed Record Holder
'13 Ram 2500 Diesel
'05 Toyota 4Runner