616/617 stripped oil drain plug

[Mark123]

I have recently had the oil drain plugs in both my cars strip. I have always been careful of the 40nm torque. Is the plug softer than the female threads in the pan? On the 240D, I was able to remove the stripped plug and put a new one in. Yesterday on the 300D. I could feel it strip at about 30nm. I could not get it to back out. Even with prying and turning.
I had an old pan, new plug, and new gasket. I swapped it out. I was careful about the 10nm on those small bolts. Do real mechanics use a little blue loctite on them? I now have a small drip on the right side of the pan. I will double check my torque. I think the gasket goes in dry, right?
I think this is the universe telling me to start suctioning out oil.

[merc lover]

this guy uses permatex gasket sealant to help seat/seal the new oil pan gasket. Also, be sure and place the copper and steel washers included in the oil filter drain kit on the oil pan drain plug before installing the drain plug. If I were in your shoes, I would purchase a new drain pain, gasket, permatex gasket sealant and oil filter change kit. I noticed the drain plug should be lightly tightened due to the same reasons you mentioned.

I started to torque mine and I could immediately tell if I had kept turning the drain plug I would have stripped the threads!

https://www.youtube.com/watch?v=YCQ_oTWhZBk

[cmac2012]

I know that feeling. I hate that feeling.

[Sugar Bear]

I'd sparingly use Permatex the Right Stuff or Aviation Form-a-gasket on the gasket. For the pan bolts blue threadlocker could be used but probably isn't necessary.

Good luck!!!

[vwnate1]

Interesting I've had to replace more than a few oil sumps because they scrape, get dented and eventually leak but never once have stripped one (wait'll my next oil change, right ?) , I hope you're using the always included new copper seal ring and NEVER EVER any Permatex as they simply do not leak when properly tightened .

As a youth long ago I stripped more than a few oil drain plugs, my solution was / is to use a short box end spanner and hold it in the middle, not from the end .

Sucking the oil out leaves all manner of sludge and dirt in the engine, it's a lazy man's dodge of doing the job correctly .

I'd think in Ore. good used oil pans are plentiful and cheap .

[Sugar Bear]

Nate I agree no sealant on the plug but would on the gasket. What are your thoughts about Threadlocker on the pan bolts? Was thinking when the gasket "squishes" you can't snug them.

[vwnate1]

I've not yet needed it , Mercedes uses a far higher grade of composite gaskets .

If you're one of those who simply must needs use RTV's, smear a tiny and thin bit over the gasket with your funger tip, never and on the bolts .

[ykobayashi]

I have recently switched to “Dowty” washers instead of the copper seals for the oil drain plug. 12mm. I bought a dozen on eBay and am still on the first one. This solved my last leak which was on the drain plug.

A Dowty washer is a steel washer with an integrated rubber seal in the middle.

[Mark123]

Thanks for the replies. I have been changing my own oil for almost 40 years.Diesel W123's since '87. I am just an amateur, but stripping the plug is a new one. I always use the copper seal and steel friction washers and don't over tighten. I assume the leak now is at the pan gasket. I replaced the turbo drain tube gaskets not that many miles ago. I have an oil suction tool and a new pan and gasket coming. Even if I have to do things twice once in while, I know I am way ahead money wise by doing my own work. And I still think it's fun.

[vwnate1]

Mark you're way ahead of the curve .

The other part is : very few good Mechanics left, mostly parts changers who don't care about doing a good job .

[ah-kay]

Originally Posted by Mark123

Thanks for the replies. I have been changing my own oil for almost 40 years.Diesel W123's since '87. I am just an amateur, but stripping the plug is a new one. I always use the copper seal and steel friction washers and don't over tighten. I assume the leak now is at the pan gasket. I replaced the turbo drain tube gaskets not that many miles ago. I have an oil suction tool and a new pan and gasket coming. Even if I have to do things twice once in while, I know I am way ahead money wise by doing my own work. And I still think it's fun.

I would check the tool box first. Using a 6 pts socket or 12 pts? My experience is that rounding bolt head probably not done by shear force but the wrong tool. Also making sure the tool is square with the head and the head is clean.

[Sugar Bear]

Originally Posted by ah-kay

I would check the tool box first. Using a 6 pts socket or 12 pts? My experience is that rounding bolt head probably not done by shear force but the wrong tool. Also making sure the tool is square with the head and the head is clean.

The OP is encountering stripped threads on the drain plug vs. a rounded hex head.

[Mark123]

ah-kay is right in general about 6 vs. 12 point sockets. I have a nice Hazet 13mm, 12 point by 14mm allen to remove the drain plug. 30 or 40 years old.
I always try to use 6 point sockets. But I am not sure if at 40nm on the plug, 25nm on filter cover, or 10nm on the pan bolts it matters that much.

[hercules]

Have done many hundred's if not thousands of oil changes on these cars, key is to always
change the drain plug, the threads stretch.
Oil leaks at this point is usually caused by a convex surface, over tightening by someone.
Repair is to flatten surface.
Always use quality parts.

[tangofox007]

Originally Posted by hercules

Have done many hundred's if not thousands of oil changes on these cars, key is to always change the drain plug...

There might be another key: don't abuse the drain plug.
I have two vehicles over 35 years old still doing just fine with their original oil drain plugs.