Last time I changed the oil and tried to tighten the oil plug with a torque wrench, it just didn't feel right so I stopped. For a while it had a bit of a leak and now since it's time for the next oil change this would be the time to do some exploratory surgery.
For an alternative repair method, and a better more detailed write up than this one:
http://www.m5board.com/vbulletin/e3...5-diy-repair-stripped-oil-pan-drain-plug.html
1) First get the car up on some jackstands, remove obvious parts, gather your tools, etc.
I wanted to examine the drain plug as is, so I drained the oil from the oil level sensor, which was pretty messy. Then on to removing the oil pan. First thing I did after removal is put it into the parts washer and clean it. It's also a good idea to do this at the end and remove any dirt and metal particles before re-intalling.
2) Removing the oil plug and examining the threads, it looks like there is some minor damage, but I guess I got overly nervous when installing the oil plug. Nothing serious, and only a little bit of running torque - I can still turn the oil plug all the way by hand. Well, since I went through all the trouble of removing the oil pan, I might as well proceed with a preventative intervention.
3) Now on to the repair. Best way to do this is set it up on a mill table if you have access to one. If not, a drill press is probably good enough. I would not recommend hand drilling! I set up dial indicator on the oil plug sealing surface. If it's badly pitted you want to take an end mill and renew the surface. Also you need to make sure that you are going to drill perpendicular to the surface and this will show any tilt that you may have. In my case it was flat and perpendicular to within a few thousandths of an inch, so I was good to go.
4) The helicoil kit tells you what drill size to use. You can use a uniflute or some cone shape thing to center the hole. Then I locked the mill table in place and proceeded with drilling and tapping.
The heli-coils that came with the kit are way too long, so I cut a few of the coils off with a Dremel tool and removed the burs on the coil edge with a needle file. This picture is after I cut two turns off. I did a fit check and looks like I need to cut two more.
5) Final result after helicoil install. The insert is just below the surface, and on the inside the tang breaks off exactly where the threads stop. Perfect fit! Drilling out the old threads does not affect the sealing surface at all. If you look closely you can still see some of the original chamfer. You don't lose any surface area between the pan and the copper gasket and the seal will work just as well as before and assuming you drill the hole straight.
The last two threads may block the oil from draining completely, but that's one of the issues with this repair. If you make the helicoil short enough to avoid that then you have only about two turns of the threads.
As a side note I think this oil pan is a really crappy design. I would have made the casting flat on the inside and then not machine away so much material for the hex head of the oil plug. So what if the oil plug sicks down another 1/4 inch? What genius designed this thing? The closeup photos show how porous cast aluminum really is. A threaded aluminum hole should always have a hard metal insert. That's just my opinion. It's also worth mentioning that if you don't have all the tools and equipment to do this right, you should find a good machinist to help you. You only get one shot at this and if you do it wrong, you've trashed a $400 oil pan.
For an alternative repair method, and a better more detailed write up than this one:
http://www.m5board.com/vbulletin/e3...5-diy-repair-stripped-oil-pan-drain-plug.html
1) First get the car up on some jackstands, remove obvious parts, gather your tools, etc.
I wanted to examine the drain plug as is, so I drained the oil from the oil level sensor, which was pretty messy. Then on to removing the oil pan. First thing I did after removal is put it into the parts washer and clean it. It's also a good idea to do this at the end and remove any dirt and metal particles before re-intalling.
2) Removing the oil plug and examining the threads, it looks like there is some minor damage, but I guess I got overly nervous when installing the oil plug. Nothing serious, and only a little bit of running torque - I can still turn the oil plug all the way by hand. Well, since I went through all the trouble of removing the oil pan, I might as well proceed with a preventative intervention.
3) Now on to the repair. Best way to do this is set it up on a mill table if you have access to one. If not, a drill press is probably good enough. I would not recommend hand drilling! I set up dial indicator on the oil plug sealing surface. If it's badly pitted you want to take an end mill and renew the surface. Also you need to make sure that you are going to drill perpendicular to the surface and this will show any tilt that you may have. In my case it was flat and perpendicular to within a few thousandths of an inch, so I was good to go.
4) The helicoil kit tells you what drill size to use. You can use a uniflute or some cone shape thing to center the hole. Then I locked the mill table in place and proceeded with drilling and tapping.
The heli-coils that came with the kit are way too long, so I cut a few of the coils off with a Dremel tool and removed the burs on the coil edge with a needle file. This picture is after I cut two turns off. I did a fit check and looks like I need to cut two more.
5) Final result after helicoil install. The insert is just below the surface, and on the inside the tang breaks off exactly where the threads stop. Perfect fit! Drilling out the old threads does not affect the sealing surface at all. If you look closely you can still see some of the original chamfer. You don't lose any surface area between the pan and the copper gasket and the seal will work just as well as before and assuming you drill the hole straight.
The last two threads may block the oil from draining completely, but that's one of the issues with this repair. If you make the helicoil short enough to avoid that then you have only about two turns of the threads.
As a side note I think this oil pan is a really crappy design. I would have made the casting flat on the inside and then not machine away so much material for the hex head of the oil plug. So what if the oil plug sicks down another 1/4 inch? What genius designed this thing? The closeup photos show how porous cast aluminum really is. A threaded aluminum hole should always have a hard metal insert. That's just my opinion. It's also worth mentioning that if you don't have all the tools and equipment to do this right, you should find a good machinist to help you. You only get one shot at this and if you do it wrong, you've trashed a $400 oil pan.