How to Remove Exhaust Flange Bolts That Are Rusty

Written by c.l. rease
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The constant heating and cooling of your vehicle's exhaust system, combined with moisture, will quickly cause the exhaust flange bolts to rust and seize. The rust has often progressed to the point that the threads of the exhaust flange bolts are unusable. To release the exhaust flange bolts, you will need to apply heat to remove the rust from the threads; and if the threads are beyond use, you will need to cut the bolts from the exhaust flange.

Skill level:

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Things you need

  • Tinted safety glasses
  • Leather work gloves
  • Striker
  • Oxy-acetylene torches
  • Fire extinguisher
  • Ratchet
  • Socket set
  • Hammer

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  1. 1

    Inspect the area around the exhaust flange bolts to make sure that there are no fuel lines or combustible materials within the area and clear any combustibles from the area underneath the vehicle.

  2. 2

    Put on your leather work gloves and tinted safety glasses.

  3. 3

    Place the fire extinguisher close to you in an unobstructed area so you can easily reach the extinguisher in case there is a fire.

  4. 4

    Turn on the acetylene and ignite the torch with the striker. Turn on the oxygen and set the flame hot by increasing the oxygen until the inner bright blue flame is about 1/2 of an inch long.

  5. 5

    Set the tip of the torch 6 to 8 inches away from the first exhaust flange bolt and heat the bolt until it has a dull orange glow then turn off the oxyacetylene torch. Do not use the air trigger to heat the bolt faster.

  6. 6

    Allow the exhaust flange bolt to cool and then place a socket that fits the bolt head onto the ratchet.

  7. 7

    Slide the socket onto the nut located on the exhaust flange bolt and turn the ratchet handle counterclockwise to loosen the exhaust flange bolt. If the first nut will not loosen, proceed to the next step. If the bolt loosens, repeat the process with the rest of the exhaust flange bolts.

  8. 8

    Reignite the oxyacetylene torch, set the flame as described in Step 4 and place the tip of the torch 3 to 4 inches away from the head of the exhaust flange bolt.

  9. 9

    Heat the bolt head until you see a bright orange glow emitting from the metal and then hit the air trigger to blow additional oxygen onto the bolt. You will see the bolt head melting and blowing toward the floor.

  10. 10

    Turn off the oxyacetylene torch and immediately strike the threaded side of the exhaust flange bolt with a hammer to remove the bolt from the exhaust flange. Repeat the procedure with each exhaust flange bolt to free the exhaust flange from the manifold.

  11. 11

    Allow the bolts and molten metal to cool for at least 30 minutes before you leave the area to ensure that no combustible materials catch on fire.

  12. 12

    Clean up and dispose of the cut exhaust flange bolts after they have cooled for one or two hours to reduce the chances of starting a fire in a garbage can.

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