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So... I stripped the bottom half of the threads due to trying to use a washer on a non-washer using drain plug. My aluminum oil pan (and plug) turns out to not be the standard oil pan for the vehicle so I have had difficulty finding the right plug size & thread.

I currently drive it still with the same drain plug. I put in oil every now and then...

What is the correct/best way to put in an oversize? Should I drill out the threads first and tap it before putting in the self-tapping plugs?
If I just use the self-tapping ones without drilling & pre-tapping, how effective is that?

Should I use the rubber universal ones?

My current oil pan plug is much smaller than the listed standard size. I got several sizes on hand of 1x Oversize plugs.

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  • What material is the oil pan made out of?
    – Pᴀᴜʟsᴛᴇʀ2 ♦
    Commented Feb 3, 2015 at 11:02
  • Also, what "self tapping plug" are you trying to use? There are probably a ton of different methods you could use to "fix" this. I just want to help you get it fixed with a solution which is comfortable to you.
    – Pᴀᴜʟsᴛᴇʀ2 ♦
    Commented Feb 3, 2015 at 11:11
  • My experience on motorcycles is that heat-cycled, vibrating components with various thread repair options only works when a professional machinist does the job, YMMV. I would evaluate replacing the oil pan with a used one as an alternative.
    – Paul
    Commented Feb 3, 2015 at 20:46
  • Aluminum oil pan. Edited the text. How do i describe what "self-tapping plug" for you? I got several of them. Mostly 1xOversize and several different sizes. Half of them are the regular standard size for the standard oil pan and half of them are what I thought the size is according to what the actual one is.
    – Zero
    Commented Feb 4, 2015 at 4:57

2 Answers 2

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This is a pretty common problem. Buy an oversized drain plug tap kit and retap your drain plug threads with the tap. The kit will also usually come with a replacement drain plug that fits the new larger tapped threads.

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  • what would the tap kit include?
    – Zero
    Commented Feb 4, 2015 at 5:01
  • 1
    This set includes a piloted drill, spring-loaded tapping tool and 5 magnetic drain plugs. Definitely don't keep driving around with a leaking drain plug. If you don't feel comfortable tapping the drain plug take it to a mechanic and have them do it. Here is the kit from amazon amazon.com/Lisle-58850-Oil-Plug-Rethread/dp/B000J19K06/…
    – esx0001
    Commented Feb 4, 2015 at 8:05
  • I'm pretty comfortable with tools and whatnot. Will this be fine if done while still on the engine? I plan on using some sort of substance to try to grab all the shavings while drilling, but will I need to file the inside face edge?
    – Zero
    Commented Feb 5, 2015 at 2:36
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    @Zero ... What esx0001 is describing should work just fine. I would utilize petroleum jelly on the drill bit & tap as a medium to collect all of the aluminum particles from the pan. When you are done with the drilling and tapping, you may also consider dumping a quart of oil through the engine with the plug out to flush anything out you might have missed. I realize this is a waste of oil, but it's better than having shavings flowing through the oil pump before it gets to the filter.
    – Pᴀᴜʟsᴛᴇʀ2 ♦
    Commented Feb 6, 2015 at 11:28
  • Thank you all, i used your advice but didnt use a tap. I will see how things pan out and will edit if things go bad lol. So far So good. =D
    – Zero
    Commented Jun 6, 2015 at 1:31
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So...
I pretty much took in all the advice you guys gave me (and from elsewhere too) and went ahead with the procedure with the oil pan still on the car.
One big difference though: Instead of using a tap, I used my oversize plug... I was stubborn and did not want to buy the tap nor take the pan off the car.

Here's how I did it:

  1. Jack the car up; stands.
  2. Drained the oil.
  3. I used an oversize "self-tapping" plug, put a glob of heavier grease all over the threads (i used silicone-based) and started tapping it into my oil pan with a smaller ratchet.
  4. I ratcheted twice (~<=1/4 turn each) and backed out once.
  5. Repeat #4 until I felt some pressure increase and then I took the plug out all the way, cleaned all the shavings off, re-grease the threads, and started ratcheting again (#4).
  6. Once I got past the middle, at some point I started to feel a lot of pressure, and was forced to switch to my breaker bar. Repeat #5 with breaker bar.
  7. Got to where the rubber gasket touched the oil pan, took out the plug and cleaned it.
  8. Re-greased and threaded the plug in, took it out, and cleaned it. Repeat a few times until the amount of shavings between the threads on the plug are minute. It became significantly easier to put the plug in now.
  9. Poured 1-2 quarts of oil in the top and took the oil plug out from the bottom.
  10. Let engine drain, clean plug, clean inside of the threads of the oil pan (i used a small towel and jammed a small part of it in and threaded it out. got a good amount of shavings out).
  11. Repeat from #9 until the inside of the oil pan threads and the threads on the plug are clean. (it would not completely stop having some amount of shavings between the threads when I took the plug out. I'm pretty sure its still grinding a little and generates some shavings as it moves in and out. It's a rather small amount of shavings and they are all stuck in between the threads (and my grease) in the middle of the threads so I feel like its okay... it was late and i got tired so I decided to stop after 1 repeat.)
  12. Put the plug in and fill car with oil, check for leaks.
  13. Start car and check for leaks.
  14. Drive around a bit and came back and checked for leaks.
  15. Seemed good for now (i also have a crank seal leak still)

This whole process took a very long time. Steps 1-7 took me 40+ minutes. I took it very slow and did it very carefully. Particularly careful with the breaker bar.

After about a month? or less possibly? I changed the oil again for good measure. Collected the oil and sent it in for UOA.
Came back relatively good. Slightly higher than baseline for iron but they didnt mention it at all in the notes. Slightly high in chrome, which they did mention, but said just keep an eye on it, its probably fine. I will see on my next UOA.

I did this sometime from mid-February to early March. It is now early June. Still running well (or at least the same as before this operation).

I would suggest others to get a threaded tap like the ones mentioned in the other answer/comments and use the right size plug for the tap. This would minimize or completely get rid of the small amount of shavings I get between the threads every time I thread the plug in.

Or take the oil pan off and do it properly.

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