If you have access to a professional-quality hydraulic lift and know how to safely use it, this is also an acceptable way to lift your car when replacing the catalytic converter.
To test the heat of the exhaust system, put on a pair of heavy mechanic’s gloves and gently brush the exhaust tube with the back of your hand. If you can’t feel any heat, you may cautiously repeat this test without the glove.
Check to see whether the converter is bolted or welded to the rest of the exhaust system at its connection points. You may need to take it to an auto shop to have it repaired if it has already been replaced and welded back into position, rather than bolted. You can still replace a welded converter if you have access to a sawzall (or similar tool) and a welding machine and know how to safely use both, but these advanced tools are beyond the mastery of most amateur mechanics.
When you’re done, move the sensor out of your way so that it doesn’t interfere with the rest of the process.
If you finish and the converter won’t seem to budge, you may want to use a hammer to knock it out of its place as long as you take care not to damage or rattle any other parts of the exhaust system (this can lead to harmful exhaust leaks down the road). [2] X Research source
Since it’s tricky to work on the converter with one hand while you hold it in place with another, for the next few steps, it can be useful to enlist a willing friend to hold the converter in place while you work or use a stand to hold it up in place.
You’ll want your bolts to be very tight. Most exhaust leaks are caused by loose bolts, so making sure your bolts are extra tight now can save you headaches in the future. [3] X Research source
Weld your converter into place by carefully joining it to the exhaust system pipes at either end. Be sure to create a secure, air-tight seal at each weld. If the pipes aren’t wide enough, you may need to heat them up and flare them to make them fit. If your pipes don’t quite reach one end of your converter, you may need to weld an additional extender pipe in. Sometimes you have to do a partial weld then lower the exhaust to finish the top part of the weld. Be sure to allow your welds to cool to a safe temperature before proceeding.
There are several ways to find an exhaust leak. One is to simply be observant while you drive — if your car sounds louder than normal when it runs or seems to “rumble” more, you may have a leak. [5] X Research source You can also check for leaks by jacking your car up, starting it in park, and carefully moving a lit candle along the length of the exhaust tubing. Leaks which are invisible to the eye should cause the flame to waver or blow out.
The worse the congestion is, the higher the pressure reading can be. Very bad backpressure readings can approach 3 psi.
However, if you don’t hear a rattle, this doesn’t necessarily mean that your converter works well. There may still be other problems with it. To be clear, this test can only tell you if you have a bad converter, not if you have a good one.
Most auto shops that offer smog testing will be able to perform these sorts of emissions tests.
