How to Remove Rusted Bolts from Exhaust (Stuck Ones!)

Updated: | Author: Steve Freling | Affiliate links may be present.

Have you ever needed to remove the bolts to the exhaust on your car only to find that they are completely covered in rust? They will not budge. You wonder how you will ever get through all the rust without breaking the bolt. Try these techniques to avoid the nightmare of breaking the bolts.

Removing rusted bolts from an exhaust when they are stuck requires time, patience, and persistence. It’s a time consuming process that can require multiple attempts. The first method to try is to apply solvent, let it sit, and unscrew the bolt. When this is not enough, hit the bolt with a hammer to break up the rust. Repeat this process several times. When all else fails, apply heat with a blow torch.

Here’s how to remove rusted bolts from exhaust without breaking the bolts.

Recommended Tools

  1. Penetrating Solvent (I recommend this one)
  2. ½ inch drive
  3. 6 sided shallow bolt socket (don’t use a 12 sided bolt socket)
  4. A small ball peen hammer
  5. A blow torch

Try a Solvent First

Thoroughly spray the bolt with a lubricant, such as Knock’er Loose Penetrating Solvent. Then wait a few minutes to let the solvent set in.

Repeat spraying the bolt with the solvent and letting it sit for a few minutes a few times. This will help loosen up the bolt. Don’t spray and then immediately try to remove the bolt. The lubricant needs to be set in for a few minutes to loosen it.

Now, attach the 6 sided, shallow bolt socket to the ½ inch drive. If you don’t have this already, this set on Amazon should have you covered.

Use the socket and drive to try to loosen the bolt. If you can’t turn the bolt with the drive, spray with the solvent again and let it sit for a few more minutes.

When you can turn the bolt, turn it gently and slowly until it comes out.

Try a Peen Hammer

Try a small peen hammer for impact to break up the rust. Hit the head of the bolt with the hammer a few times. Then, try loosening the bolt again with the socket attached to the driver.

Apply Heat with a Blow Torch

You tried the solvent several times and the hammer, but the bolt still can’t be removed. Now what? You will need to apply heat with a blow torch like this.

Use the torch to apply heat. Applying heat cleans the bolt threads of rust and corrosion. Apply heat on the area that surrounds the bolt. Do not apply heat directly to the bolt.

Repeat this process until the bolt is loosened and comes out.

Alternative Ways to Remove Rusted Bolts from Exhaust

Cutting the Nut

Instead of using the lubricant, hammer, and torch to unscrew the bolt, another method is to cut the nut to the bolt.

To do this, you will need a very sharp chisel and hammer.  The chisel edge and sides need to be very sharp to cut through the nut.  Use the hammer to hit the chisel in order to break the nut.  Once the nut is cut through, you can easily remove it and unscrew the bolt.

Using a Blow Torch and Water

Heat the bolt until it’s very hot with the torch. Then, immediately cool it with water. Repeat this process until the bolt can be removed with your fingers.

The extreme temperature change between the torch and cold water makes the bolt shrink. Once the bolt shrinks, it will be easy to unscrew the bolt.

Using the Hammer to Break up the Rust

Some people recommend lightly tapping the bolt with the hammer. Others recommend tapping the bolt hard several times with the hammer. Once the rust is loosened, unscrew the bolt.

Need to Remove Several Rusted Bolts?

  • Start with the first method by applying the solvent and waiting a few minutes to let it set.
  • Do not completely unscrew each bolt. Instead, unscrew partially and then tighten the bolt. This will prevent some of the bolts from breaking if there are several bolts that need to be unscrewed.
  • Again, if the solvent is not enough to loosen the bolts, apply heat with a torch.

Bottom Line

You may need to try some or all the methods mentioned above to remove rusted bolts from an exhaust. You should begin with the easiest method of applying solvent. Only use heat when none of the other methods work.

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About Steve Freling

Steve has worked for more than 20 years as an automotive mechanic, and later run his own repair shop for both cars and motorcycles. He's a maintenance freak, and generally pretty good at troubleshooting!

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