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Aluminum on Drain Plug Threads

I did an oil change yesterday and, as I was getting ready to replace the drain plug, I noticed about 1 turn (360 degrees) of aluminum around the threads just below the bolt head. I threaded the material off the plug - it came off easily - and found that I was able to finger thread the plug back in and it went smoothly. The remaining threads seem to hold just fine. One day and 30 miles later, there are no signs of leakage. How concerned should be?

This is the first oil change that I’ve done myself in years (only the second one on this vehicle) - out of laziness, I’ve almost entirely deferred to the dealer (convenient hours, friendly service, and low prices - and most importantly, they have never tried to sell me any service that wasn’t legitimately needed). While I didn’t need a hammer, or anything like that, to loosen the plug, it did take a little more force than I thought would be necessary. Is this indicative of over tightening on all of those dealer oil changes?

For all I know, these threads could have been hanging out on the plug for a few years now. Maybe I didn’t think enough of it at the time, but am I thinking too much of it now?

She currently has 80K (miles) and gets oil changes every 3-5K, depending upon usage in between.

If you had a choice you want all the aluminum to stay on the pan but 1 threads worth of transfer is nothing to worry about. Are you using a new crush washer each time, this should become a rule for you.

That isn’t something that I learned growing up, but sounds like cheap insurance that I should start buying. I think I’ll be doing the oil changes myself from here on out. Sheesh - 4 older brothers (1 a mechanic), and they all taught me to reuse the old washer. Of course, back then, aluminum oil pans were reserved for race engines, so we also never dealt with aluminum drain threads. Thanks for the response oldschool.

I’d want to inspect the threads in the pan. A borescope should work perfactly for this. If the threads are damaged beyond the first one or two I’d want to helicoil the hole.

The damage should the plug fall out on the highway could be extremely expensive. even a new engine. I’d want to se sure those threads are good and not make any assumptions.

I’d find it hard to believe that one turn of thread is stripped and the other threads are not pulled, which means the thread pattern is distorted.

Overtightening the plug and/or reusing a crush gasket can cause this and odds are it was caused by someone overtightening the plug at some point, or many points.

Aluminum would make me a bit antsy and if the vehicle were mine I’d keep an eye on it until the next oil change and then install a thread insert just for peace of mind.

Is this something that I’d be better to take to a independent shop, rather than the dealer (assuming they may have caused this as they have done all but one of the previous oil changes)? There is an independent in my neighborhood that gets positive reviews in the Mechanics Files here. The dealer has always treated me alright, but I also like the idea of supporting the local entrepreneur (not that the dealer isn’t one as well). Perhaps I could have them do this when it’s due for the next oil change (before we do hit the highway for summer vacation).

An independent shop can do this without problem. Borescopes and oil plug repair (helicoil) kits are items that every shop should have.

I personally would not wait until the next oil change. The risk is too great.

I would install one of these to keep things from getting worse.

This has always bugged me. Why would they not purposely make the plug preferentially sacrificial over the bung? Which is harder to replace, the pan or the plug? Duh! Yet, we almost aways see the plug destroying the bung when it is over-torqued. It’s been this way whether the parts are some form of steel or aluminum. The two are fairly close on the galvanic series and even so, there are numerous alloys of either and various heat treating methods available to make one part more sacrificial than the other. Make the plug so it fails before the bung! Geez.

Cost. To use an aluminum pan they’ed have to install an insert to make the pan threads stronger than the plugs. And making the plugs even weaker than the pan might leave them to strip out too easily.

In truth, there’s absolutely no reason why a pan or a plug should strip. The only reason they do is that people either overtorque them or don’t take the time to start them properly and crossthread them.

Perhaps if they molded into the pan in big letters right next to the hole "CAUTION: MAXIMUM TORQUE XXX). Of course, gorillas can’t read, can they?

Indeed, this seems to be the problem with the oil change pit in a large garage (such as many dealers have). The low man on the list gets the oil changes because it is a straight forward procedure. The same seems to hold with tire rotations - now that I think about it, I’m pretty sure that they’ve overtightened lug nuts - to the point that I’ve had to put a pipe on my lug wrench and hop on it to get them loosened. I’ve had tires inflated to the number on the sidewall instead of the number on the door sill. Maybe I’m less enamored with the dealer than I thought.

That little rant out of the way, the problem is when shops don’t properly teach people on these stations how to properly perform these fundamental tasks and testosterone is substituted for thought. Unfortunately, when an owner is simply trying to keep their vehicle well maintained, these are the pieces of the vehicle that most frequently get touched, but by the least gentle of hands.

To say “you are the only shop that ever removed this plug so if any issue developes regarding this pulg I will hold you responsible” does not take into consideration that an issue can develope that is not caused by the behaviour of the plug remeover (meaning a poor design or the selection of poor materials or perhaps the cutting of the threads in the pan or on the plug could be the cause).

Bolsheviks! Whether the pan has a threaded boss or an insert, just make the plug out of a softer ALLOY than the pan is cast from or the insert is made of. That doesn’t cost any more than what they’re doing now, it’s spec’ing out a different material for the plug. Seriously, I think I have two vehicles with cast aluminum pans and STEEL plugs! While I have never stripped a drain plug in my life, it’s obvious from the number of people who post about it that it happens rather frequently.

If everyone exercised the proper care, none would fail. But they don’t! so why not make it FOOL PROOF? If something can fail through misuse, make it the part that costs the least and is the least disruptive to replace.

I understand your point, but if they used a softer alloy on the plugs there’d be stripped out plugs everywhere. The plugs would be too soft. The other problem would be in applications where the plugs were longer than the pan thickness at the hole. The plugs would strip out in the center and just spin, being held in by the threads ono the end and almost impossible to remove.