Some of you may remember my stripped oil drain plug saga of several weeks ago. I was able to obtain and install a new oil pan and gasket without problems, and put in a new oil drain plug, along with a copper washer. The washer, plug, and pan were acquired by my mechanic. (At 100% markup from what I could have bought them from Fastlane for, I have discovered! but I guess the guy had to make a little scratch somewhere.)

Since then, I've had a leak, a fairly significant one in the way that a small head wound can be significant -- it makes a mess, a puddle about the size of half a dollar bill overnight, but isn't seriously affecting the oil supply (I check the oil level every few days and haven't had to add any in the couple hundred miles since this ill-fated oil change). The underside of the engine was so filthy from years of crud accumulation, however, that I just wasn't sure where all the oil was coming from. I could see where an oil drip was building on the pan under the drain plug whenever I was under the car, but I thought, surely all this oil isn't from that silly plug.

Well, I washed the engine Saturday evening, drove it around a bit to dry things off afterwards, and parked it on a clean dropcloth for a while, wiping all around the pan and plug. Went back a while later, and it's obvious all that leaking oil really is coming from the drain plug! The rest of the pan is pristine above the plug and around where it bolts in, yet all this oil puddles on the floor directly under the pan's plug. And I'm pretty sure I didn't strip or cross these threads at installation, as the plug went in easily and was put in by hand, then tightened with a wrench.

So my questions are, is there some gasket or washer I should have used in addition to the copper washer that came with the drain plug? Or should I be using some sort of sealer or tape on the plug threads themselves? Also, I did not use a torque wrench on the plug -- should I have?

Also, is there anything wrong with my plan of just letting the thing drip until the next oil change, replenishing with oil as necessary, rather than dumping out all that nice Mobil-1 after only a couple hundred miles?

Who would think one oil change could create such mess?

Just let it drip until the next oil change. Make sure you are using the correct diameter copper washer.
You spring for the Mobil 1 ?

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Normally, no sealant of any kind is needed for the oil pan drain plug. A good plug with a new copper O-ring should seal perfectly. I'd wonder if your mechanic supplied the correct parts...? A torque wrench normally isn't needed, if you know by "feel" how tight to make the plug. If you're not sure, a torque wrench may not be a bad idea. Woudn't want to strip the plug again...!

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Boise, ID
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I spring for the Mobil-1, it was good enough for the P.O., so I'm sticking with it! And the car really runs quite well on it

Maybe in prep for the next oil change, I'll order a new plug from FastLane (they're cheap, what the heck) and use the new washer from the oil filter package, and see what that does for me. *shrug* Should I be torquing it to some amount, perhaps? Or is tightening it 'pretty tight' with a wrench good enough?

The copper washer, if it is the correct size, is all that you need to prevent the drain plug from leaking. If it does leak, there is a likely problem with the seating surface on the lower pan. It probably makes no sense to look at it now, unless you want to drain the oil.

However, the seating surface, underneath the washer, must have quite a good finish and be free of any corrosion. Normally this is not a problem because the surface always has oil on it when the drain plug is reinstalled. But, if the pan was removed from a vehicle quite some time ago and the surface sat around and corroded somewhat, then the copper washer cannot seal properly.

I had the identical problem with a rebuilt caliper that I purchased from PepBoys. No matter how many copper washers I tried, I could not stop the brake fluid leak under pressure. Took a careful look at the seating surface and there were three very tiny divots in the surface. Not enough to make be believe that was the problem. Took the caliper back, got it exchanged, reinstalled the washer and no leak. It takes very little damage to the surface under the copper washer to start a leak.

Of course, I am assuming that the surface on the underside of the drain plug has not been damaged and does not have any dirt on the face when you installed the plug.

The pan, plug, and washer were all brand-spanking new. So perhaps my washer was the incorrect size...

The only possibility is that the washer was too large. It should have quite a close fit to the bolt. The clearance should be about .030 per size, maximum, and the outside of the washer should be of the approximate diameter as the head of the bolt. Take a look at the washer, now, while it is installed. Can you see more of one side of the washer sticking out than the opposite side? Is the washer approximately the same size as the bolt head (maybe just slightly larger) or is it quite a bit larger?

The only other possibility is that you are a bit scared of torquing the bolt properly due to your last experience. It is not all that easy to strip the thread out of the bolt. You remember all the effort that you put in the last time. You might want to get a torque wrench and use it to be sure. The bolt should be torqued to 30 ft.-lbs. It will not leak if you reach this torque level.

Thank you Brian, I will check when I get home!

Remember that a copper washer is supposed to be a one time use.... but I think this whole deal of trying to seal hot oil with metal gaskets only is crazy...
So try this ... which is my procedure for ANY gasket anyway....
be sure you have the correct washer... clean it and put as thin a coat of red RTV on each side as you can spread with your finger...and let cure overnight... any gasket needs SOME give to it... some compressive ability to seal against metal....
If you put really flat metal under the microscope you find that only about 10 percent of the metal is actually touching....that is steel to steel.... but the idea you can crush aluminum or copper or brass also depends on the flatness of the two surfaces relative to each other... if one is a degree off being flat then you are squeezing more some place than another... a prescription for leaking....
That leak... over thousands of miles could easily make that mess under the car... and if you go with the " let it leak and watch" that mess will come back...
I have seen copper washers which had concentric rings made into them... that is another possibility...

Those concentric rings are found on copper washers used on brake systems. The rings touch down on the irregular surfaces that you speak of, Greg, and they actually crush a little bit. These washers, if you can find them, are excellent.

I have reused these washers on brake systems and have been successful when a brand new flat washer would not make the seal.

The RTV will probably work fine if all else fails. But, if the washer is the correct size and the pan is new, I don't see how it will leak if the bolt is torqued to anything past hand tight.

oil drain plug 30Ft.-lbs/40 Nm

The washer for the oil drain plug appears to be exactly the size of the base of the drain plug, which I think rules out an improperly-sized washer. Given my squeamishness from stripping the first bolt, combined with the fact I do not yet own a torque wrench, I think it's likely the bolt isn't tight enough. I will acquire or borrow a torque wrench and make it right. If that doesn't do it, I will try leathermang's RTV tip on a fresh washer at next oil change, after hopefully ruling out any surface irregularities on the pan itself. I'll report back at the next oil change

Thanks for all the help!

Since the washer is the correct size, the bolt is not tight enough. You must crush the washer somewhat if the surface of the pan is slightly out of flat (which is typical). Torque it to 30 ft.-lbs. and it will likely stop the leak.

Of course, you can always follow Greg's idea with the RTV, but I don't think you will need it.

If you have the right crush washer, either the plug is not tight enough or there is some dirt, etc. under the washer. If the latter is the case, you don't have to wait until the next oil change. Loosen the plug (don't remove) and clean underneath the washer with a cloth or toothbrush. If it's not the right washer, you can remove the plug and put your thumb over the drain hole and not spill more than a few drops of oil. Push in on the plug as you loosen it. When you have it unscrewed, slide your thumb over the hole as you remove the plug. Just have someone to help you and do the job when the engine is cold. Have a drain pan in place just in case. If you tighten the plug with a combination wrench, it is unlikely that you will over torque it.

With new parts, it's also possible that some casting flash or a small piece of metal where the drain hole threads were cut got left behind.

As for RTV, I've never seen it help with drain plugs. The reason metal (copper or aluminum) and plastic washer gaskets are used, is because they crush to seal and they also take the tightening of the drain bolt much better.