My 318ti project has a leaky oil drain plug. It was an M12 bolt, but the previous owner threw in a 1/2" bolt once he stripped it out. It still leaks. I'm thinking of getting some teflon tape and another oversize drain plug with a piggyback plug to solve the issue. Then I can do all my drains from the piggyback plug.
What says GRM'ers?
Looking for a cheap but permanent fix.
We'd usually go 1 size bigger, if that didn't/couldn't work, then we'd go piggy back, if that didn't work we tried to sell an oil pan.
Piggy back usually worked though.
In reply to bigdaddylee82:
You'd sell some poor bastard your leaky oil pan? 
Steel or aluminum pan? Can you weld, if so with what equipment?
Aluminum pan. Can't weld.
I'm really hoping that a 1/2" oversize piggyback plug will work with my problem. Should I add the teflon tape or threadlocker to the oversize plug to make sure there are no more leaks?
In reply to MINIzguy:
The piggy backs we used, were self tapping, and had some kind of rubber/plastic gasket between the oil pan and flange of the bolt/plug, no other sealing material needed.
How about heli-coil? It's what we usually do. Drill, tap, clean, heli-coil, and rock on.
blaze86vic wrote: How about heli-coil? It's what we usually do. Drill, tap, clean, heli-coil, and rock on.
This.
1/4 or 3/8 pipe plug? Tap pan and use shop vacuum to keep chips out of pan.
You could drill & tap the plug for a piggyback.
In reply to MINIzguy: I would try running an original-size tap into the hole to clean up what's left of the threads, and then use a new drain bolt (with all its original thread metal intact) and sealing ring. The sealing effect comes from the sealing ring being compressed, not from the threads, as in a pipe thread.
If that doesn't work, you can still go oversize.
I'll keep the Helicoil in mind.
But I am worried as I don't know what size to use, whether it be re-tapping, oversize or Helicoil.
Originally, it was a M12. Now I have a 1/2" bolt (12.7mm) that I don't know if it is oversized or not. The only markings on the bolt is 1/2" with nothing stating OS from what I recall.
What should I re-tap with? 1/2" again? I can't go back to M12 as it would be too small.
Page down to #11 post.
In reply to MINIzguy:
Id think .7 mm oversize is about how big the helicoil bore would be. So you'd not be removing much material that hasn't already been.
Watching some YouTube videos on a Helicoil, I would have to drill out the hole, tap and then helicoil, right? Wouldn't that now make my hole even bigger than 1/2"? Or would a 1/2" helicoil account for the bigger size so I don't have to worry?
And how would I keep my shavings out of my oil pan the best I can? Run a magnet after drilling, and always run a magnetic oil plug?
You would helicoil at m12 if the hole isn't too big for it already, and I dont think it is, drill diameter for a m12x1.75 helicoil is 12.5mm, You'd have a pretty smooth hole running a drill that big through a 1/2" threaded hole. In some cases like this you can get away with just running the helicoil tap through the damaged oversize threads, but I dont recommended that.
And yes, drill, run in the coil tap, spin in the coil, reach in and break off the end, flush it out by dumping a quart or two of cheap oil, or maybe diesel fuel chased with oil, through the engine, screw in a standard plug with new fiber washer, torque to spec, done.
I'm understanding it now. Tap size for my 1/2" is 29/64" which is less than 12mm. So a M12x1.75 helicoil tap is 12.5mm so I would be peachy perfect. Awesome! Thanks for the help guys!
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