I've seen quite a few posts lately by folks that have had problems with oil drain plugs stripping out. This is a VERY common problem with oil drain plugs and there are all sorts of aftermarket "quick fixes" for it. Some work ok, some not so good. But, why does this problem happen in the first place? Well, there are quite a few reasons. One is that this plug is removed and installed a lot (hopefully) and the threads just wear out. After all, the flange in the oil pan with the female threads is a non-hardened piece. The drain plug is hardened. So, the weakest link is the threads in the flange. Of course, most of our cars are very old by now and those with original pans have lots of wear on the drain plug threads.
Another problem according to some is over-torquing. I'm sure this does happen, but I don't think it's really all that widespread of a problem. Most folks install and torque these with an open end or box wrench and you just can't apply that much torque with such a wrench. In fact, I believe this is why GM changed about 1968 from the 7/8" head size to the 9/16 head size. A 7/8 open end or box wrench is a lot longer than a 9/16 and a lot more (and excessive) torque could be applied.
Another problem, of course, is cross-threading. However, I don't even think that this happens as often as folks think. For one thing, oil drain plugs have a long pilot on them. This reduces the chance of cross threading, but does not completely eliminate it.
I believe that none of the above is the biggest reason for oil drain plugs stripping out, though. I believe the biggest reason is road grit that seems to inevitably wind up on these threads. The grit, being quite abrasive, wears out the threads in the non-hardened flange plate. So, what to do about it? Well, here's what I do:
After I remove the drain plug, I not only wipe it clean, I use a brush to clean any grit from the threads. I use a small, brass wire "toothbrush". Then, I clean the threads again with solvent.
Next, after the oil has drained, I use a small, round brass wire brush (a rifle cleaning brush works well) to "scour" the threads in the flange plate . I rotate the brush and pull it DOWNWARD (so as not to allow any of the grit to be pushed up into the pan. Lastly, I use a pipe cleaner soaked with solvent to final clean the threads.
When all is said-and-done, when you install the drain plug, it should go in SMOOTHLY with no "gritty" feel to it. If there is a "gritty" feel, you have not cleaned the threads well enough. Don't bother to remove it and clean some more---any damage is mostly done. Just make sure to do a more thorough job the next time.
Yes, this procedure does take more time and you're not going to find ANY "quick lube" shop guys that are going to do it. But, it should prevent, or, at least, prolong the day of the absolutely DREADED and SICKENING feeling when the drain plug "won't tighten".
Another problem according to some is over-torquing. I'm sure this does happen, but I don't think it's really all that widespread of a problem. Most folks install and torque these with an open end or box wrench and you just can't apply that much torque with such a wrench. In fact, I believe this is why GM changed about 1968 from the 7/8" head size to the 9/16 head size. A 7/8 open end or box wrench is a lot longer than a 9/16 and a lot more (and excessive) torque could be applied.
Another problem, of course, is cross-threading. However, I don't even think that this happens as often as folks think. For one thing, oil drain plugs have a long pilot on them. This reduces the chance of cross threading, but does not completely eliminate it.
I believe that none of the above is the biggest reason for oil drain plugs stripping out, though. I believe the biggest reason is road grit that seems to inevitably wind up on these threads. The grit, being quite abrasive, wears out the threads in the non-hardened flange plate. So, what to do about it? Well, here's what I do:
After I remove the drain plug, I not only wipe it clean, I use a brush to clean any grit from the threads. I use a small, brass wire "toothbrush". Then, I clean the threads again with solvent.
Next, after the oil has drained, I use a small, round brass wire brush (a rifle cleaning brush works well) to "scour" the threads in the flange plate . I rotate the brush and pull it DOWNWARD (so as not to allow any of the grit to be pushed up into the pan. Lastly, I use a pipe cleaner soaked with solvent to final clean the threads.
When all is said-and-done, when you install the drain plug, it should go in SMOOTHLY with no "gritty" feel to it. If there is a "gritty" feel, you have not cleaned the threads well enough. Don't bother to remove it and clean some more---any damage is mostly done. Just make sure to do a more thorough job the next time.
Yes, this procedure does take more time and you're not going to find ANY "quick lube" shop guys that are going to do it. But, it should prevent, or, at least, prolong the day of the absolutely DREADED and SICKENING feeling when the drain plug "won't tighten".
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