Whether you are a new mechanic, experienced mechanic, or someone who just likes to do their own maintenance, eventually you will run into the infamous problem of having a stripped or rounded off drain plug that you won’t be able to put a wrench or socket on. As a technician at a dealership, I see this all the time and in the beginning I didn’t know what the heck to do but now I have the knowledge and tools to battle any stripped or rounded off drain plug.
Let’s talk for a minute about how this happens. The most common ways for this to happen is by unskilled technicians that mostly work at Jiffy Lube and Take 5 (places like that). Now, I’m not discrediting these places because for a cheaper oil change and faster time to get it done I think the idea of it is great. Also, I don’t want to discredit he technicians because they probably just have received the proper training to do oil changes. The problem with these places is that they rush their technicians and when you rush someone in the automotive industry, there will be mistakes. Using the wrong size wrench or socket (even just one size bigger) can eventually round off a drain plug. Just because it “fits” doesn’t mean its the right size. For example, most newer Mazda drain plugs are 17mm (despite the stupid inverted H8 plugs they also have). When a new technician comes in, I immediately tell them that and not to use an 18mm or adjustable wrench (never use an adjustable wrench on a drain plug). Another good example is cross threading. If you start threading in a drain plug or any bolt for that matter, if it isn’t threading on with ease, stop and take it out and try again. Lastly, never (and I repeat this with the utmost importance) use any kind of impact to remove and reinstall a drain plug (this is an absolute no no). Also, it’s always good practice to use a small torque wrench for reinstalling drain plugs. Look at your manufacturer’s recommended torque spec, but in most cases you’re looking at anywhere between 25-30 ft lbs. On Mazda’s, I set my torque wrench to 30.
How to Remove rounded off / stripped drain plugs
So, you have finally run into a rounded off or stripped drain plug and you’ve probably tried a few things like pliers, hammering on a smaller socket, using a hammer by itself, etc. In a pinch, I have use Knipex pliers with some good force but I only use them if I absolutely know there is no saving this plug. Knipex Pliers are quite literally the best pliers ever. Here’s a set on amazon that I use:
Every good mechanic that I know has a set of these pliers or something very similar in their tool box. The other way to get a stripped or rounded off drain plug removed is to use a bolt extractor set. These sets comes with a few things. The first thing they come with are sockets that will fit the correct size socket of the bolt you are trying to get off. These sockets have sharp edges in the points so that when you are turning them, they will bite into the bolt head and most of the time will get it to turn. The set also comes with drill bits. One set of drill bits will be for inverted drain plugs (like hexagon plugs). These types of plugs get rounded the most because people just don’t know what type of socket to use for them. I’ve seen people use Torx bits or even Flathead screw drivers with a wrench on the end. The drill bits in the bolt extractor kits are tapered so that when you drill into them it will bite into them and get them out. Lastly, the set comes with regular drill bits if you need to just try to drill the plug out. Here’s a link to a great bolt extractor set:
If you’re just a lube technician or even a mechanic that has some experience, these bolt extractor kits are literally life savers. In the automotive industry, we don’t have a lot of time to mess around trying to get a bolt removed. With this kit, you just pick the size you need and take it right off whether its a socket or drill bit.
In conclusion, it always sucks when you get rolling doing oil changes and you get a vehicle on the rack and see a stripped or rounded off plug. I remember when I first started, I freaked out when I saw something like this because I really had no clue what to do. After all, knowledge is the best thing you can have to further your career as a technician. After seeing this a few times as a new technician, one of the more experienced technicians would always pull his kit out and get the plug off easily and I have a rule that if have to borrow someones tool 3 times I get it myself. I now have the pliers and the bolt extractor kit and I use them almost weekly.
If you have any questions or if there is an article you’d like to see on this site please email me at lubetechcurt@gmail.com. Thank you and I hope you found this information useful.
