How to Change Exhaust Flange Gaskets

Written by tim petruccio
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How to Change Exhaust Flange Gaskets
The exhaust flange gasket is rounded to allow a swivelling movement between the front and rear exhaust without separation of parts. (Nick M Do/Photodisc/Getty Images)

Replacing the exhaust flange gaskets on a vehicle can be a difficult task, depending on where the exhaust flange sits underneath the vehicle. Exhaust flanges are designed to be a semi-flexible joint in the exhaust, which allows for movement of the front and rear exhaust parts. The exhaust flanges allow some movement without the risk of the front of the exhaust separating from the rear of the exhaust. Exhaust flange gaskets are also called doughnut gaskets.

Skill level:

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Things you need

  • 3/8-inch-drive ratchet and socket set
  • Open-end wrench set
  • 2-ton or greater capacity jack
  • 2 jack stands
  • 2 vehicle ramps (replaces jack and stands if available)
  • New exhaust flange gasket
  • 1 can PB Blaster or penetrating oil
  • Flathead screwdriver

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  1. 1

    Lift the front of the vehicle using a 2-ton or greater capacity jack. Set jack stands beneath either lower ball joint or the ends of each axle housing just behind the front wheels. You can drive the vehicle up on lifting ramps for this step, which will eliminate the need for a jack and jack stands.

  2. 2

    Lay beneath the front of the vehicle and slide your body into position where you can see the exhaust flange. The exhaust flange is the link between the front exhaust and the rear, so the flange will be located anywhere from 6 inches to 1 foot behind the engine.

  3. 3

    Remove the bolts that fasten the exhaust flange together, using a 3/8-inch-drive ratchet and socket on the bolt, and an open end-wrench on the nut. If the hardware is stuck or rusted, you may need to spray the entire assembly with PB Blaster or penetrating oil.

  4. 4

    Slide the old flange brackets off of the ends of the exhaust pipes. The flange brackets are the pieces of metal that look like a football cookie cutout and squeeze together to compress the flange gasket. Remove the old flange gasket or doughnut gasket by using a flathead screwdriver to pry it free from the front exhaust pipe.

  5. 5

    Slide the new exhaust flange onto the front exhaust pipe. Slide two new exhaust flange brackets onto either end of the exposed exhaust pipes, with the smooth side of each flange bracket facing out.

  6. 6

    Insert new hardware bolts through both flange brackets and start a nut on the ends of both bolts, using your fingers. Make sure the bolts are protruding through to the front of the vehicle. Insert the bolts from rear to front.

  7. 7

    Tighten the bolts and nut combinations to approximately 60 to 80 foot-pounds of torque. Tighten the flange brackets together evenly. Do not tighten one side down then the other. Tighten one side two turns, then the other side two turns. Tightening the bracket unevenly will cause the gasket and flange brackets to not be able to create a proper seal.

  8. 8

    Lower the vehicle and start the engine. Place a jack underneath the rear of the vehicle and lift it gently if you hear any hissing or exhaust leaking. The exhaust flange and gasket that you just installed will swivel into place if you lift the rear portion of the exhaust.

Tips and warnings

  • When changing your exhaust flange, inspect the rest of the exhaust underneath your vehicle. Pinpointing possible leaks or potential problem areas can help you immensely. Remember, the longer the exhaust is on the vehicle, the more oxidation and rust sets in, making the exhaust harder to repair or patch.
  • Never lift a vehicle on uneven ground or a slope. Lifting on uneven ground or slopes can cause jacks and jack stands to collapse. Failure to adhere to this warning could cause property damage, personal injury or even death if you are under the vehicle when it collapses.

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