Exxon Valdez in My Garage

[saread]

Well not quite.  But, I changed oil last week and used an aftermarket crush washer and noticed a drop of oil on my pristine garage floor. Well, that's downright Soviet I'm thinking. So, I check all around and the only thing I noticed was a wet plug.  Nuts.   Down to the local BMW store to get a proper crush washer and I dropped the fluid and replaced the cheapo junk part with the real deal.  Warm things up, all looked good, and I think I'm done.  Nope. Next morning there's another baby oil slick forming under my ride.  Well, crud.  Now, I'm no genius, but I think I can put in a bung without messing it up.  Righty tighty and lefty loosey kind of stuff is right up my alley.  At this point I'm confused and starting to think there may be alien treachery at work.

The only thing that I've noticed is that both of the new crush washers, after market and BMW, are stamped pieces. The old washer that didn't leak was the factory washer and it was machined on both sides.  I'm thinking that the washers I got from the BMW dealer might be imposters as well and that this application may just require a machined face on both sides of the seal.  This weekend I will reinstall the factory seal (these are not really crush washers) and see if that makes a difference.  If not, we will be speaking to the dealer about a solution.  Hopefully something that doesn't involve copious amounts of silicone rubber, teflon tape, or a diaper.

[Grumpy Goat]

Hmmmm … I’m wondering if it is something other than the drain plug washer. I have bought washers for various bikes from various places (including of Amazon so likely Chinese) and never had any drain plug leaks. Be interesting to know how this all turns out.

[saread]

Hmmmm … I’m wondering if it is something other than the drain plug washer. I have bought washers for various bikes from various places (including of Amazon so likely Chinese) and never had any drain plug leaks. Be interesting to know how this all turns out.

Exactly. Hence the alien conspiracy theory.

[Lee]

When you drain the oil again run your finger on the sealing surface of the sump and the threads to see if you can feel any imperfections.
Also run your finger on the drain plug checking for imperfections.

[saread]

This is maddening. I put the original crush washer in last Saturday. No luck. Still have the drip. I did have a really good look at the plug and can't see any issues with it at all. The threads are great, the sealing surface seems good. The BMW washer that is stamped from aluminum does deform when torqued. The washer I took off was flat on both sides and the rolled edge from being cut from a sheet was gone and squared off. It also looked like it had full contact on both sides. I did not run my finger over the sump surface, but I'm seeing no issues with the washer surface.

I gave it a comprehensive look for other sources, like the oil filter. It was pretty clear it's the drain plug. I've changed oil in all sorts of vehicles, like a thousand times. I know that you put in the plug with your fingers so you don't cross thread, and that you don't overtighten it. I'm skeptical of torquing plugs as torque specs are almost universally too high and tend to strip the plug. Although I did torque the last two washers (very carefully) to comply with the BMW recommendation. Ultimately, I could try a flexible washer and see if that works. I've done that with hammered pans and it does work if the bung isn't too deformed. But before I get there, I think a conversation with my local BMW house will be occurring.

In the meantime, I'm putting a HD sticker on the beast.

[Grumpy Goat]

This is maddening. 
...
But before I get there, I think a conversation with my local BMW house will be occurring.

In the meantime, I'm putting a HD sticker on the beast.

I think that is appropriate. 

[saread]

Update.  I think I may have solved it, or at least massively slowed it down.  Last weekend I drained the oil to get a look at the sealing surface on the sump and take another look at the plug.  I ran my finger over the area on the sump and I can't feel anything there.  Here's a bad photo of what was there: 
   

I did grab a little Brillo pad, some solvent, and gave it a good going over to be sure there wasn't some rogue gunk on there.  Seemed like a dead end though.  So, I turned my attention to the drain plug.  Still, it looked fine and I couldn't feel anything strange on the flange surface.  But that didn't necessarily mean that all was good.  I had a look at the sealing surface under a microscope and along the edges of the flange you could see areas where the plug had been beat up, raising a few very small burrs along the outside edge of the sealing surface.  I don't remember ever dropping the plug, but that doesn't mean I didn't. I just don't remember. The burrs were very small, raised up probably .005" or less and couldn't be seen with the naked eye.   They were on the perimeter and that raised a question of if they even mattered.  I put on the old crush washer and sure enough, the outer edge rested on the burrs. Smoking gun?  I don't know.  You would think that the crush washer would deform enough to seal the small discrepancy in the surface.

I grabbed some stones from the bench and went to work on the flange surface. These are not ordinary garage stones, they are very fine, very square, very flat, stones used for gunsmithing work.  It didn't take long to burnish the burrs off.  On with a new crush washer, torque to 31 ft-lbs (42 N-M for you metric types), fill with oil, and see what happens.  So far, no hideous oil slicks under the bike.  I'm not totally convinced that I've solved the issue.  Time will tell that. I do know that on the next oil change it will be getting a new, carefully examined, drain plug.

All of this still boggles me.  There is nothing I found that the crush washer shouldn't seal around.  We're not sending people to the moon here.  Just trying to keep fluid from leaking out of a hole.  This is definitely not brain surgery.  But, then again, I'm an American engineer, not a German one.  My idea of precision for a specific application may differ.

[Grumpy Goat]

...
All of this still boggles me.  There is nothing I found that the crush washer shouldn't seal around.  We're not sending people to the moon here.  Just trying to keep fluid from leaking out of a hole.  This is definitely not brain surgery.  But, then again, I'm an American engineer, not a German one.  My idea of precision for a specific application may differ.

Agreed 100%. This Canadian engineer would have had far less patience and tolerance than you, given the level of "swiss-watch refinement" of these powertrains. Thankfully my RS has not presented such a challenge to me yet.

Speaking of plugs ... I replaced the drain plugs in both my engine and FD with Dimple magnetic plugs some time ago (not sure if they are still in business since the URL does not work) and have no similar issues before or since. If changing the oil drain plug you might want to consider similar. A stronger magnet won't hurt.

[saread]

Yeah, it looks like Dimple has given up their web presence. I don't know if that means they are still in business or not. Dimple plugs can still be found listed on some web sites, so I may be able to acquire one. Gold makes a M20x1.5 magnetic that might be a good alternate choice. Although, I do wonder about the corrosion potential using a stainless plug in an aluminum case. That may be overthinking things a tad.

I was bored last night so I grabbed one of the used crush washers and got to measuring its thickness. Thinking that if the sealing surface on the plug was not plane, it would show up in the crush washer. There was a definite divot in the crush washer. The max thickness was about 0.0480 inches (or a scosche over a millimeter for the rest of the world). The min area was about 0.0455 inches about a third of the way around from the max area. Two and a half thou ain't much. But it does raise the question of if I did drop the plug and bent the flange? Maybe stoning out the burrs also leveled the sealing surface some. Don't know. New plug for the next oil change and a new day.

I suspect Grumpy Goat would have the patience for this. Solving problems is what we do.