Stripped drain plug

[chronic_sonic]

After an oil change, the drain plug on my 2012 Sonic (1.8L, 5 speed) could not be torqued to 10 ft*lbs. The plug threaded into the pan, but just kept spinning and spinning with little to no resistance.

I looked into the threaded hole in the oil pan and the threads appeared to be stripped.

I chased the threads in the oil pan with an M14x1.5 tap and bought a new M14x1.5 drain plug. I threaded the new drain plug into the pan but once again it just kept spinning.

I bought another M14x1.5 drain plug but this time with a longer grip length. I threaded it in until it became snug then torqued it to 10 ft*lbs.

I figured that the depth of the drain plug hole in the oil pan was greater than the length of the OEM drain plug, and that the longer drain plug was able to thread into some previously unused threads in the oil pan. However, after looking at some photos of aftermarket oil pans, it seems like the drain plug is longer than the hole is deep, and that the plug protrudes into the oil pan.

Has anyone seen the inside of an OEM oil pan to confirm what is greater, the depth of the hole or the length of the drain plug?

The attached photo shows the protruding drain plug of an aftermarket oil pan.

 

[Z71]

As I said in another thread on this subject, I do not recommend torquing fasteners that are heavily coated with oil, as the resulting preload on the bolt and stress in the threads will be about twice as high as for a dry bolt. And torque values are typically specified for dry fasteners. Therefore, 5 ft-lbs torque on a well oiled fastener will be roughly equivalent to 10 ft-lbs torque on a dry fastener. Whether the drain plug protrudes into the pan is immaterial as long as it does not interfere with any engine moving parts and actually means that all of the threads in the pan are used which is the way it should be. I always thread in oil drain plugs into aluminum oil pans carefully and only to the point where they feel snug. I I have several motorcycles, all with aluminum oil pans and steel drain plugs. I have never stripped any of the oil pan threads doing it this way, never had any of the drain plugs come loose, and I change oil in all of them every year, in addition to changing them in my cars, including my Sonic.

Once you damage threads, especially aluminum threads, chasing the threads will not repair them, only enable you to thread in the fastener without any interference. You will still need to either enlarge the hole and cut new threads and get a larger drain plug, or get a new oil pan.