How To Replace an Exhaust

Repco | 6th Feb 2024 | 6 minutes to read

There is nothing worse than hearing the sound of a hole in the exhaust pipe. It makes your car sound noisier and the hot exhaust gases may be causing damage to the underside of the vehicle from where they are exiting the hole. In this example the exhaust manifold and catalytic converter (cat) were OK, it was just the two sections of tail pipe that had corroded. It contains both mufflers and exhaust pipes that went from under the driver's seat and exited at the rear of the vehicle. The choice was made to replace it with a standard factory style exhaust system and not a performance upgrade as the car is to stay factory stock.

If you have a hoist the replacement is simple and easy otherwise as in our example, you can use a good quality jack and axle stands to do the job. The 2-piece system was ordered online as were the replacement rubber mounts and gasket. It is important to change these as well as they are relatively inexpensive and if the old exhaust is rusted through, then the mountings may not be in that good a shape.

Note that replacing an exhaust can be a lengthy and challenging process and, as with anything that involves jacking up a vehicle, it can be dangerous. With this in mind, if you are unsure about the process, it is always best to have a professional mechanic do the job for you.

This is also a general guide for replacing an exhaust suffering from a leak, so things will likely differ vehicle to vehicle.

Why Do Exhausts Corrode?

The main reason for corrosion of an exhaust is water in the exhaust pipe. As an exhaust cools, the water vapour and some acids that are part of the combustion process cool in the exhaust pipe and condense. This causes standard mild steel exhaust pipes and mufflers to slowly corrode internally. If you look at your exhaust pipe on engine startup, you will notice water being spat out the back of it. It is also why the front part of the exhaust connected to the engine, lasts longer than the back part as it is hotter and will contain less water vapour.

Short trips before the exhaust has time to really heat up makes the problem worse than a long country drive. If you want your exhaust to last it is best to get it made from stainless steel. Stainless steel will eventually corrode but it resists the corrosion process much better than normal mild steel.

Step by Step Guide To Weighing Your Trailer

1

Check where the exhaust leak is coming from.

  • Jack up the vehicle and place it on axle stands. Jack it as high as you can while still being safe as removing and replacing the exhaust takes some room to manoeuvre it out and in. Before climbing under it, shake the vehicle when on stands to make sure it is stable. You also may want to use safety glasses when working underneath the car to stop dirt and debris falling in your eyes.
  • Once safely on axle stands, check the exhaust for visible damage or corrosion.
  • Idle the engine and check for the exhaust leak.
  • It may be a simple fix, like tightening a loose clamp.
  • Make a list of what needs to be replaced/patched up and apply any temporary repairs to keep the vehicle driving.
  • Don't forget to include any mounts or brackets that hold the exhaust to the car body.
2

Order in the Parts Required.

You'll want to choose whether you want a standard replacement or upgrade to a performance system.

3

Remove the old exhaust pipe(s).

  • Jack up the vehicle and placing it on axle stands. Make sure you perform all the safety checks mentioned in step 1.
  • Undo any temporary repairs that were used to hold up the exhaust. It comes in sections so remove a section at a time starting from the back of the vehicle where the exhaust gas exits the pipe.
  • Most exhaust have rubber mounts between the exhaust and vehicle body. These can take a bit of wrestling backwards and forwards to get them to come off. If replacing them with a new one just cut them off. Otherwise, some lubricant like WD40 will help them to slide off.
  • Metal clamps can be undone with the help of a penetrant, wire brush and a socket set. If too badly corroded an angle grinder with a metal cut off wheel will help. If using this wear safety equipment like glasses, earmuffs and gloves. Also be aware of where the hot metal sparks generated by the cut off wheel are ending up. You don't want to start a fire.
  • The same method can be used for exhaust flanges that have nuts and bolts or nuts and studs to hold them together. Usually this will be at the catalytic convertor end of the exhaust. They contain a gasket between the 2 flanges to help it seal. The gasket needs replacing as once it has been used, they are crushed and will not seal as good as a new one.
  • Once the section of exhaust is disconnected from another section and the brackets holding it to the body have been removed, take it out from under the car. This may take some twisting and swearing to get it out.
4

Compare the exhausts.

Compare the Old Exhaust to the new Exhaust by laying the old section of pipe next to the new section and do a comparison. Check for:

  • Pipe contours and bends matching, otherwise it may not fit.
  • Connections at each end of the pipe are the same or similar.
  • Verify that any body mounting brackets are in the same location and are the same size and shape. Use the old section as the template as sometimes brackets on the new can get bent in transit and need adjusting.
  • There are occasions where you may need to remove a bracket from the old system and reuse it on the new one.
  • Check any mounts and clamps and replace if necessary.
5

Install the new exhaust pipe(s).

  • Reverse the removal process to fit the exhaust pipe sections
  • Rubber body mounts go on a lot easier than they come off. If difficult, a little bit of rubber or silicone grease can help them slide on easier.
  • Clamped sections of exhaust pipes are an interference fit. Test fit the sections together when they are off the vehicle. It can be difficult to do it under the car so making sure they slide together before mounting them saves more swearing.
  • If you want your exhaust nuts and bolts to last and make them easy to remove, replace them with stainless steel ones and add some anti-seize lubricant.
  • As you add exhaust sections, check clearances on the car body and components. You may need to tweak some brackets to get the result you need. Especially where the tail pipe goes through a cut out in the rear panel.
6

Time to test the new exhaust.

  • Let the car idle for 5 to 10 minutes.
  • Check for any exhaust leaks around the joints. Use your hand and go around the joint without touching it. If leaking, you will feel it blowing on your hand.
  • If it seems ok, shut it down and let it cool.
  • Re-check any nuts and bolts to make sure they are tight.
  • Then you can remove the axle stands and lower the car.
7

Test drive the car.

Lastly, take the car for a test drive and listen for any exhaust rattles. If there are none, your job has been successfully completed. If you get one:

  • They can be hard to pinpoint and may only happen at certain points in the drive. Try and get as much data on the rattle as possible to help you figure out where to look.
  • Bring the car in and jack it up and put it on axle stands.
  • Inspect the exhaust system. Let it cool and give it a shake with your hand. Sometimes the spot causing the issue is obvious, other times you may need to make adjustments based on trial and error.
  • Keep testing and tweaking until it is found and fixed.

Finishing the Job With Repco

Replacing an exhaust is messy and like any maintenance job, you should do some homework on it first. You don't want to get half-way through it and decide it is all too hard. It can be done with a jack, axle stands, and simple hand tools, all of which you can pick up at your local Repco or online. We also stock exhaust parts such as exhaust manifold gaskets, exhaust kits, and mufflers. Remember preparation is key to getting a good result.