Whether it’s through being careless or just getting old, there’s a good chance that you’ll strip the threads of some bolt or stud at some point. This is particularly true of threaded fasteners that are tapped into aluminum vehicle engine blocks and cylinder heads. Having to buy replacement bolts is one thing, but scrapping a component like a water pump or intake manifold due to stripped threads can be quite expensive.
Fortunately, there are engineering solutions to fix these issues without having to purchase a new part. These include using a kit that provides thread repair inserts to re-tap the hole and give it a strong, permanent hold. These kits are inexpensive and easy to use, making them a great solution for those with time constraints.
The thread repair inserts used in the kit come with instructions This website that include a step-by-step process for drilling, tapping and installing the insert. They can be used on a wide range of fasteners, including hex head bolts and nuts. The kit also includes a tap tool and tang break tool that makes the installation process even easier.
When using the kit, start by removing the old bolt or stud and using a thread checker to determine the actual thread size of the damaged hole. Using the kit’s drill bit, square up with the damage and carefully clear out the existing threads by enlarging the hole slightly. It’s best to do this in a cold area, like outside, so you don’t get any shavings stuck to the inside of your car or truck.
Next, the kit will come with an aluminum rod or tube that’s the correct size to fit into the damaged hole. Drill a hole into the body that’s the proper diameter for the rod or tube, install it and then chamfer the ends to ensure there are no spots where weld hardening could occur. Then use the included Loctite to weld the rod or tube into the body.
After welding, the rod or tube must be trimmed down to the proper length and re-tapped with the same thread pitch as the original bolt. The resulting repaired threads are now stronger than the original aluminum bolt or stud and should be able to withstand any application pressure.
While this solution is a great option for those with limited time, it’s not very good for high load applications, such as the bolts that hold the cylinder head onto the block. A more durable, permanent solution would be to remove the cylinder head and weld the head bolt holes with a flux-less, gas-shielded welding process.
While this may be a more time-consuming process, it’s the best way to guarantee that the threaded bolts are as strong as possible and won’t strip or fail due to over-tightening or corrosion. It’s important to note that, no matter what solution you choose, the original bolt must still be tightened to the proper torque specifications to avoid loosening the gasket and leaking oil, coolant or combustion gases.