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I have a 2008 Audi RS4 with a slow oil leak from the oil drain plug. I have added about 1 qt/1000 miles lately to give you an idea of how much is leaking. I have been told by a repair shop that the leak is because the oil drain plug / crush washer and the oil pan have some kind of warping and the crush washer will not seal like it should anymore. They are recommending replacing the (lower) oil pan. (The RS4 has an upper and lower oil pan. According to the shop, only the lower needs to be replaced.)

Does the explanation that was given to me make sense? Is this really how the oil pan seals? Do I really need to replace the lower oil pan?

Thanks in advance!

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  • Do you have a photo of the lower pan? I'd be curious to see the extent of the warpage they're talking about.
    – raydowe
    Commented Mar 15, 2017 at 18:05
  • I would not expect a drain plug and washer to have warp, but oil pan is possible, especially if something has been run over, but it would need to be a relatively significant buckle, so that one side of the compression washer is completely compressed and the other is lose. Did they try a new plug/washer first? Are you able to crawl under and take a look - should be visible? perhaps someone over torqued it and took out some threads could be another explanation
    – Chris
    Commented Mar 15, 2017 at 18:10
  • It does make sense that they would only replace the section of the oil pan that has the drain hole (I'm guessing the lower unless it has a really wacky setup. If the upper pan isn't damaged, then no need to replace it. It's only going to cost more to do so. No idea how common pan warping is though.
    – atraudes
    Commented Mar 16, 2017 at 23:43

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A new plug and washer, then remove the pan and grind and polish the mating surface flat if a new one is too expensive is a possibility.

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  • I wasn't sure if grinding down the surface was a possibility. Good to know. I wanna say they didn't have a new plug laying around, so a new plug is the first place I'm gonna ask them to start.
    – Matt
    Commented Mar 17, 2017 at 3:25
  • take care about how they are made though : those with the boss on the outside are ok, but if the thin metal is on the outside and the boss is internal it may not be possible as you can end up with just a big hole...
    – Solar Mike
    Commented Mar 17, 2017 at 6:37
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It's possible. I could be wrong, but I've never heard of an oil pan warping on it's own. A more likely cause would be hitting something like a rock and denting it in an unlucky spot.

I would check the oil pan to see if you can spot any damage. A cynical person might suspect that someone overtightened it and damaged the threads.

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  • They showed me the oil pan when the discovered the leak. I didn't see any damage anywhere. And yeah, I've been known to be cynical...especially after I had a terrible dealer experience a few years back.
    – Matt
    Commented Mar 17, 2017 at 3:24
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It sounds fishy that the oil pan would warp. The crush washer is intended to "crush" down and fill in any gaps between your oil plug and the oil pan. I'd try simply replacing the crush washer first to see if it stops the leak. Crush washers should be replaced regularly. Some recommend replacing them with every oil change.

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    Once I damaged threads on the oil pan and have to repair it. Now on I always replace crash washer.
    – oryades
    Commented Mar 16, 2017 at 6:54
  • They replace crush washer with every change. I'm not looking over their shoulders or anything, but it's supposed to happen every oil service.
    – Matt
    Commented Mar 17, 2017 at 3:23
  • by warping do you maybe mean that the threads were damaged? If the oil plug was cross threaded once when it was put in, or if it was overtightened that could potentially cause a leak
    – rviertel
    Commented Mar 17, 2017 at 4:25

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