Subaru's are great because of the light aluminum blocks. Unfortunately they are also cursed because it is very easy to strip threads anytime you get to work. Over my years on this website I've seen quiet a few people complain about stripped threads, and I've seen a few ask how to fix them, so I hope this will help anyone in need in the future.
Ok, first of all, the classic sign of a stripped thread is a bolt that's meant to go into that hole will no longer screw in appropriately. It can start to go in at an angle, stop half way in, wont catch threads on attempts to screw in, or the threads no longer hold it in place.
This is a classic picture of stripped threads., if you look carefully the threads are destroyed.
(This is a picture of a valve cover bolt threads that are stripped)
![Image]()
The tools you will need are:
1) A drill
2) Appropriate Size Drill bit (depending on the hole you're fixing)
3) A Tap (sizes vary depending on size of hole)
4) An insert or a Heli coil (sizes vary depending on size of hole)
5) A Tap wrench for optimal results
![Image]()
Before you begin you have to find out exactly what kind of thread pattern your re-tapping for.
Based on this finding, you will determine exactly which insert or heli-coil you're going to use. Ideally you want to be able to use the exact same bolt that was originally intended.
Once you have this figured out, any local screw store will have the appropriate size insert or heli-coil. (inserts are much cheaper than heli coils and use standard taps, which will save you a huge chunk of money)
Each insert and heli-coil have outer and inner threads. They also come with a specified drill and tap size that you need to purchase to be able to match the outer threads. (All of the taps I've ever seen have written on them the appropriate drill size).
Now assuming you have all your equipment here's the process:
1) Using the appropriate drill size, drill at a straight angle into the threads you are re-tapping. (If you're working in an area where you can't remove the metal shavings, use reverse drill bits so that the debris will come outwards)
![Image]()
You should have a smooth surface now.
![Image]()
2) Using the tap, begin to re-thread the hole. Remember to go about 1.5 turns in and 0.5 turns back out. If you ever feel like it's getting hard to push, turn back, never force is.
(I'm not using a tap wrench because I lost it, but for best results a tap wrench is preferred)
![Image]()
When you are finished with step 2, you should have clean looking threads:
![Image]()
3: Now it's time to put in the insert or the heli-coil in place. To secure an insert in place there are seal lock applications you can use to keep it in. The red substance around the threads is seal-lock.
![Image]()
4: Inspect and test your finished product. Make sure to clean up all the metal debris to prevent damaging other parts.
![Image]()
![Image]()
![Image]()
I really hope this gives someone a good insight regarding the process that goes into re-tapping stripped threads. If there are key things I missed or said something that's not true please let me know and I'll modify it.
Also, please add any tips and information.
Good luck everyone,
~Daniel
Ok, first of all, the classic sign of a stripped thread is a bolt that's meant to go into that hole will no longer screw in appropriately. It can start to go in at an angle, stop half way in, wont catch threads on attempts to screw in, or the threads no longer hold it in place.
This is a classic picture of stripped threads., if you look carefully the threads are destroyed.
(This is a picture of a valve cover bolt threads that are stripped)
The tools you will need are:
1) A drill
2) Appropriate Size Drill bit (depending on the hole you're fixing)
3) A Tap (sizes vary depending on size of hole)
4) An insert or a Heli coil (sizes vary depending on size of hole)
5) A Tap wrench for optimal results
Before you begin you have to find out exactly what kind of thread pattern your re-tapping for.
Based on this finding, you will determine exactly which insert or heli-coil you're going to use. Ideally you want to be able to use the exact same bolt that was originally intended.
Once you have this figured out, any local screw store will have the appropriate size insert or heli-coil. (inserts are much cheaper than heli coils and use standard taps, which will save you a huge chunk of money)
Each insert and heli-coil have outer and inner threads. They also come with a specified drill and tap size that you need to purchase to be able to match the outer threads. (All of the taps I've ever seen have written on them the appropriate drill size).
Now assuming you have all your equipment here's the process:
1) Using the appropriate drill size, drill at a straight angle into the threads you are re-tapping. (If you're working in an area where you can't remove the metal shavings, use reverse drill bits so that the debris will come outwards)
You should have a smooth surface now.
2) Using the tap, begin to re-thread the hole. Remember to go about 1.5 turns in and 0.5 turns back out. If you ever feel like it's getting hard to push, turn back, never force is.
(I'm not using a tap wrench because I lost it, but for best results a tap wrench is preferred)
When you are finished with step 2, you should have clean looking threads:
3: Now it's time to put in the insert or the heli-coil in place. To secure an insert in place there are seal lock applications you can use to keep it in. The red substance around the threads is seal-lock.
4: Inspect and test your finished product. Make sure to clean up all the metal debris to prevent damaging other parts.
I really hope this gives someone a good insight regarding the process that goes into re-tapping stripped threads. If there are key things I missed or said something that's not true please let me know and I'll modify it.
Also, please add any tips and information.
Good luck everyone,
~Daniel
