How to Replace a Donut Gasket

by Jody L. Campbell
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Exhaust "donut" gaskets don't exactly live the sweet life. Squeezed like cream filling between the single hottest part of your engine and the heavy exhaust system that follows, the donut gasket is subject to a remarkable amount of stress, hardening and degradation over time. And once the donut hits its expiration date -- between the noise of leaking gases and potential for carbon monoxide poisoning -- you'll probably find the time you spent replacing it worthwhile. Better than frittering it away on something else, anyway.

Step 1

Lift the vehicle all the way up on the car lift. You could try using a jack and jack stands, or a set of ramps, but this job can require a good bit of working space. Your particular vehicle will dictate the approach.

Step 2

Determine if the front exhaust pipe is a Y-pipe. This would mean that it attaches to the engine at dual manifold locations on both the left and right side, then downstreams into a single chamber pipe. If this is the case, you will need to remove both front flange-to-manifold connections. If it is only a single-chambered pipe, you will only need to remove the single flange-to-manifold connection.

Step 3

Set up the ratchet, extension and appropriate sized socket for the nuts on the manifold studs and make sure the ratchet is set in the reverse position.

Step 4

Light the torch, choose one manifold stud nut to heat and heat it to a cherry red color. Quickly shut off the torch and apply the ratchet, extension, and socket to the nut and back it off the stud. If you feel any resistance, relight the torch and re-heat the nut some more so you do not break the stud.

Step 5

Remove all the nuts from the manifold studs using this procedure. Take your time and be careful not to break any studs.

Step 6

Put on the safety gloves and back the front pipe away from the manifold. Use the pry bar for leverage to help; you may have to slip off some of the hangers downstream on the exhaust system to allow some movement and flexibility.

Step 7

Allow the pipe and manifold to cool down some. Remove the old gasket and insert the new one. Allow everything time to cool down. Re-thread or chase the manifold studs with a new nut or thread-cleaning cleaning die to straighten out and smooth the threads. Failure to do so can result in exhaust leaks due to uneven bolt torques.

Step 8

Replace the nuts and tighten with the ratchet, extension, and socket. Specific torque values for your vehicle will vary, but the important things are that the bolts are tight, and evenly tightened. Most mechanics will default to 25 foot-pounds of torque for smaller 7/17-inch studs, or as much as 50 foot-pounds for larger ones. In any case, go over all the bolts at least three times in sequence to make sure they're evenly tightened.

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