Rethreading an oil pan plug

Anyone had any success rethreading a leaky oil pan plug? I'm willing to re-tap the drain whole, but I don't wanna end up with metal filings cycling through the engine.

I've heard that a replacement plug can sometimes self-correct the problem, but I don't want to make anything worse.

jokabgunter said:

Anyone had any success rethreading a leaky oil pan plug? I'm willing to re-tap the drain whole, but I don't wanna end up with metal filings cycling through the engine.

I've heard that a replacement plug can sometimes self-correct the problem, but I don't want to make anything worse.

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Replacement "oversize" plugs are usually made to form threads - vice cutting them - so you shouldn't get metal cuttings..

Also, if you do need to cut the bung in the pan, keep the tap flutes packed with chassis grease, and be sure to back it out and clean it (and repack the flutes) often so you'll trap and remove the metal cuttings. I've done this on spark plug holes with a good deal of success (and without removing the cylinder head!)

using a replacement plug or a tap to reform threads rub a lot of wax in the drain hole and on the tap or plug any filings will stick to the wax

jimgrms said:

using a replacement plug or a tap to reform threads rub a lot of wax in the drain hole and on the tap or plug any filings will stick to the wax

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If threads are "formed," the metal is moved to make the threads - but not cut (you can also get "fluteless" taps that do a similar job.)

If threads are "cut," then there will be cuttings that need to be controlled.

As I'd said, check the plug. If you don't see flutes on it (most I've seen don't have them,) then you've got a "thread-forming" plug, and there won't be any cuttings to worry about. You also get somewhat stronger threads when they're formed vice cut - because the metal is re-arranged (this is why I don't like cutting threads on screws - it's better to get a different screw that fits. You weaken a screw when you cut threads on it.)

Even when reforming thread it is possible to get metal particles and wax or chasis grease is cheap

why not just replace the pan? The gasket probably leaks anyway, and you would get the opportunity to make sure your bottom end is ship-shape, aswell as make sure the pickup screen is clean.

What about teflon tape on the plug threads?

darjevon said:

why not just replace the pan? The gasket probably leaks anyway, and you would get the opportunity to make sure your bottom end is ship-shape, aswell as make sure the pickup screen is clean.

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Regardless of whether or not you want to replace the pan, I'd remove it either way. That way you can get the filings out should there be any.