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How to Remove Broken Exhaust Flange Bolts


When working on the exhaust system, you may run into broken or corroded bolts on the exhaust flange or at the exhaust manifold. Broken or sheared off bolts are often a result of movement by the manifold due to the expansion and contraction from hot to cold. The bolts will rust and corrode due to their exposure to the elements. There are three ways to remove a broken or corroded exhaust fastener:

  • Heating the corroded fastener
  • Welding a nut onto the broken fastener
  • Drilling out the broken fastener
Exhaust Flange Bolts
Exhaust Flange Bolts

Heating the Corroded Fastener

Heating the fastener before removal either with a torch or induction heater may break the rust loose. Be sure to have the proper safety equipment before starting. Be mindful of plastic fuel lines used on some vehicles. An induction heater is a safer option over a torch. Heating up a rusted fastener before trying to remove it may save you from having a fastener break on you.


Heat the fastener until it is red.


While the fastener is still red, try to just tighten the fastener just slightly. This will help break the bond from the rust. Then try loosening the fastener.


Remember that the removed fastener will still be very hot along with the area that was heated up.

Welding a Nut on a Broken Fastener

If you have experience with welding, this can be a good option for removing bolts that have been sheared off. The heat from the welder helps free up the fastener and welding on the nut gives you something solid to grip onto. Be sure to have the proper safety equipment before starting.


Take a nut with an inner diameter about the same size of the damaged bolt.


Weld the inside of the nut to the top of the broken bolt.


Use a wrench or socket wrench to remove the broken bolt.

Drilling OUt the Broken Fastener

Using a drill and an extractor tool, you can remove a broken bolt. To avoid damage to other engine parts, it can be helpful to use a manifold drill template to help keep everything straight. Since there are different manufacturers of drill templates, it is best to follow the instructions that come with the tool.


Get started by first grinding the broken bolt flush with the head and then using a small drill bit to make a pilot hole in the center of the bolt.


Before drilling more, make sure you don’t drill too far. On a good bolt hole, measure the depth by taking a paper clip or the drill bit and marking the depth with tape. This will help you determine how much further you need to drill.


Once the pilot hole is started, switch to a larger drill bit. Continue to check the depth until you have drilled to the desired depth.


Use an extractor to get the bolt out.


If the bolt refuses to come out, further drilling to the proper size to either rethread the hole or installing a thread repair insert may be necessary.

The Fel-Pro® Advantage

Fel-Pro offers replacement fastener kits for many applications to replace aged, damaged and corroded fasteners. These complete kits come with all the fasteners (studs, bolts and nuts) to do the job correctly. Don’t take a chance on reusing an old fastener. It may break during the installation or later down the road. Fel-Pro replacement fasteners come with pre-applied organic coatings to resist corrosion. Some kits come with self-locking nuts to help retain the clamp load on the joint. Find the right Fel-Pro part to complete your repair.


Learn more about Fel-Pro quality gaskets that are specifically designed for the repair environment, find your car part, or find where to buy your auto part today.

The content in this article is for informational purposes only. You should consult with a certified technician or mechanic if you have questions relating to any of the topics covered herein. Tenneco will not be liable for any loss or damage caused by your reliance on any content.

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