So I changed the oil on my 86 240 this past weekend, a first for me. Once the operation was completed I scouted under the car for oil leaks and noticed a drip coming off the oil drain plug. I wiped the plug clean and waited to see if the drip returned, and it did. So I get a drip off the oil drain plug about every 15 minutes. I have a few theories as to why I'm getting this leak which I will list below. Any feedback or thoughts on my leak problem will be much appreciated.

Theory 1: Bad crush washer. I didn't replace the crush washer and just reused the one that was on the plug.

Theory 2: I stripped the threads on the oil pan. I don't think this theory is that plausible as I didn't use all my might when tightening the oil drain plug.

Theory 3: Bad drain plug. On a previous oil change I had my mechanic swap out my old drain plug with an FCP Groton magnetic drain plug. I've read on this forum that some folks have had leak issues like mine with these.

Theory 4: Debris between crush washer and oil pan. The day I changed my oil it was kind of windy. I changed the oil in my driveway, which is dirt/gravel/sand. I fear that the wind may have blown dirt in and around the drain hole on the oil pan. I wiped the drain hole before putting the drain plug back in but maybe this was not enough.

New IPD magnetic drain plug with new crush washer and my oil drip was no more. Many thanks to the brickboard community.

Thank You all very much for the feedback, it is greatly appreciated. I ordered some crush washers and a couple oil drain plugs from IPD (one magnetic and one regular). I'll throw the IPD magnetic drain plug on with a new washer and see what happens. If the drip continues I'll swap out for a standard oil drain plug and see if that changes anything. I'll let you know what happens.

I tried the magnetic drain plug and it leaked. You could do a quick swap with your original plug (lose very little oil) and see if it still leaks. Don't forget the washer.

I doubt that it matters what type drain plug you use. Its not the threads that seal it is simply the crush washer (a soft compliant aluminum) being pinched between two surfaces.
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David Hunter

I sand the copper washer smooth on both sides and reuse it. Never had a leak in the 15 years that I've been doing this to the same washer.
Dukester
'85 244 M46 221K Miles

I'm shocked to read that folks here are not changing the copper washer more frequently.

When you take the plug off the pan, you need to replace the washer, every time. Never reuse old washers.

It's really no big deal, as the washers cost a whole 50 cents. If they were expensive I could understand reusing them, but they are not.

Tighten the plug to 47 ft/lbs using a torque wrench.
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http://dylans122.blogspot.com

Hi Dan,

I think you have had the answer all a long. The other comments are all right on too.

The reason I'm writing to throw in a little more insight, if that is possible. I’m sure I’m about to say nothing new to most people.

The copper washer material work hardens as it is distorted (crushed) to fill in the micro imperfections on the pans surface. The washer also takes up space if there is any out of parallel surfaces caused by variances in thread fit tolerance.

With that said. I felt the yawns and oh yeah, what is your point.

I change the washer every other time. I torque to the low limit the first time then to the high limit the next. I make sure I put the washer back the way it was on the first time. Both torque limits have been tested to confirm that the pan bolt won’t come out with the one with the looser thread fit.
Nylon sealing washers when used are considered being cold formed. I’m not aware if you can reuse them or how many times.

Now on occasion I have notice a slight film around the plug on the second use.

This bring me to an experiment that I’m about to run. I have saved a lot of used washers. I’m thinking about heating them up as a batch and then quenching them. This will anneal the material back to like new.

They will be a little thinner but just as soft like single ply toilet tissue over two ply. No, I don’t reuse that stuff, if you are thinking that way! It’s a man thing, sorry ladies!

I just need to make up my mind if I should file them smooth before hand. I’m thinking they will crush again as before. A little more thinner but I don’t foresee a problem until it is too big to stay under the head. At least one more shot.

I was wondering what consensus I could get, on this experiment, from those that have been so forth coming with their knowledge. Has anyone done this?

Phil

Hi Phillip,

I've been annealing my copper crush washers for the last 30 years. Must have read something somewhere with my motorcycles. With the 240's, I have about 10 and when I'm down to the last one, I bring them in the house and use two sets of needle nose pliers to hold them over the gas burner on the stove til cherry red. We've put 350K miles on those 10 crush washers.

I bring them back outside (when cool) and on the work bench I use some emery paper (or sand paper) to get the crud off both faces.

I can honestly say that I've never had a leak at the drain plug.

As an aside, about 5 years ago I purchased a magnetic drain plug and when I first attempted to install it "it didn't feel right" as the threads were not an exact match to the oil pan. The magnetic drain plug still sits on my shelf and if anyone wants it, just pay for postage.

Marty Wolfson

Hi, Marty - I believe your memory is correct. I recall an old repair manual for my 500 Triumph twin that called for placing the copper head gasket on a stove burner until red hot, then quenching in cold water and reusing it. That was probably to save money on the frequent "decoking" called for in the manual. Maybe it was the heavily leaded gas of the day or maybe the Brits were just into decoking (removing combustion deposits).

If it will work on head gaskets, surely it has to work on the drain plug washer.

FWIW, I use a new one every 3rd or 4th oil change - cheap insurance against the pricey Mobil-1 dribbling out.
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Bob: son's 81-GL, dtr's '94-940, my 83-DL, 89-745(V8) and 98-S90. Also 77-MGB and some old motorcycles.

That fcp grotten magnetic drain plug leaks, I have one of them and I do not use it.
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DD-1990 240 DL SW M47II FI 3.1 234 K miles

For the record: Out of a hundred or more oil changes on various vehicles that I've performed (lots of 240s), I have NEVER changed the copper washer and NEVER had a leak from the plug. Make sure you put the used washer on the same way it came off and you'll never have a leak. That drain plug doesn't need to be eyeball-popping tight, either. I would suspect the aftermarket plug. Check the seat on the oil pan for burrs, too.

Charlie
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1985 244DL B230 M46 170k

Theory 1 is the correct answer. I don't replace that copper washer often or until I notice oil around the plug just before draining.

Seems like you have pretty much answered your own question. When I tried to cheap out on the crush washer, I had a very minor leak, a drop or three overnight. When I spent the additional $1.00 for the copper washer it disappeared. You might try a little gasket sealant on the drain plug threads plus with a new washer.

Not to beat a dead horse, but I also had a leaking aftermarket drain plug and switched back to my original. I do use a new crush washer, usually no drips, sometimes I have to give it an extra tug if I see a drop. Funny thing is I changed oil on a 79 for 10 years w/o using a crush washer (I just re-used the big copper washer it had) and never had a leak.

I don't want to help you beat that dead horse either. I will help you bury it though.

I want to say thanks to the other posters like OLDSEAHORSE for vindicating my reluctance to throw away copper and try to reuse them. I have a kinship to copper, pennies.

The big copper washer is the crush washer we are talking about. One person did mention aluminum as a material. You have to be careful with aluminum. It comes in various forms of temper and grade because it is a man made alloy metal. Copper is pretty much copper. When we change it, we try to give it a different name, not just a number. An example is brass and bronze etc.

Now that’s old school thinking!
Phil