Subaru Catalytic Converter

FAQs— Subaru Catalytic Converter

1. I know that I can’t work on my catalytic converter while the exhaust system is still hot. How can I properly test the temperature of the system for me to know when to start with my cat con replacement?

You can do that by wearing a heavy-duty mechanic’s gloves and, with the back of your hands, gently brushing the exhaust tube. If you can no longer feel any heat, try to repeat the test without the glove. Just be careful to avoid getting burnt. If it is still hot, let it cool down for a few more minutes before trying to test it again.

2. I was doing a DIY fix on my Subaru catalytic converter but I recalled that during the last time I had it replaced by a mechanic, it was welded in place. Is the job feasible for an amateur DIYer like me?

You can still do the repair by yourself even if the cat con is welded to the exhaust system at its connection points. However, you should make sure that you have access to a sawzall as well as a welding machine and you know how to use such equipment safely. Remember that these are advanced tools and may be beyond your mastery.

3. During troubleshooting, I noticed that my Subaru catalytic converter is bolted in place. However, the bolts have already rusted. Any tips on how to properly remove such bolts?

Partially corroded and rusted bolts or those that have jammed into the nuts can really be kind of difficult to remove. It helps if you loosen up the said bolts by putting on penetrating oil and allowing the oil to seep into the bolts so that it can lubricate them for a few minutes before you remove them using an appropriately sized wrench.

4. After installing my new Subaru catalytic converter, what are the easiest ways to check if my DIY task has caused exhaust leaks?

If you want to check for exhaust leak without physically getting under the vehicle and checking the pipe, you can drive test your ride and observe the exhaust behavior while you drive. If you notice that the car growls louder than usual or when it rumbles more than normal, there may be a leak in the system. Alternatively, you can jack up your ride, start it in park, and slowly move a lit candle along the length of the exhaust tubing. The flame will wave or blow out when it gets in front of the leak.

5. What can possibly happen if my Subaru catalytic converter gets backed up with debris, soot, and other byproducts of exhaust?

This can affect the engine's capacity to rid itself of exhaust, therefore causing a big drop in your vehicle's fuel efficiency. Worse, the soot and debris can make the engine stall. When this happens, perform a backpressure test. Such test can be done by screwing a pressure gauge into the oxygen sensor's slot on the converter. When the engine is operating at 2,000 RPMs, the pressure reading should be less than 1.25 psi. If there’s congestion, you’ll get a higher reading.

6. A friend told me that I can use a mallet to test my old converter. Is that true? If yes, how can I perform the test properly?

Yes, a rubber mallet can tell you if it’s already time to replace your old converter. With the rubber mallet, give your catalytic converter a firm hit. If there’s rattling from the inside, that means the converter now needs replacement as its metallic catalyst has begun to crumble and corrode.

7. Instead of replacing my dirty Subaru catalytic converter, can I clean it first? Is it worth a shot?

Yes, you can take the catalytic converter off your Subaru and try to clean it to eliminate the soot and debris that are causing the catcon to malfunction. You can clean it using compressed air or a catalytic converter cleaner. When using the former, you have to remove the core and use 90 psi maximum compressed air. This is enough to blow away ash, dust, and light accumulations. When using a catalytic converter cleaner, on the other hand, make sure to strictly follow the instructions that come with the cleaner for best results.

Toxic emissions, low fuel economy, poor engine performance, and bad exhaust-this is what a faulty catalytic converter can do. If the device can't effectively transform toxic compounds such as hydrocarbon, carbon monoxide, and nitrogen oxide into less harmful substances, the bad catalytic converter can ruin your driving experience and the vehicle can fail the emissions test. Install a new Subaru catalytic converter. Here's how:

Required skill level: Intermediate to Expert

Needed tools and materials

1. New catalytic converter
2. Jack and jack stands/Hydraulic lift
3. Ramps
4. Wrenches
5. Penetrating oil
6. Hammer
7. Sawzall (for a welded-in catalytic converter)
8. Welding machine (for a welded-in catalytic converter)

Preparing for the job

Lift the vehicle off the ground, not just one corner. Raise it with a jack and support it with stands or use a hydraulic lift. The vehicle has to be parked on a level surface. Don't start any work on the catalytic converter until you're sure that the vehicle's exhaust has cooled down. You have to slide underneath the vehicle to trace the lines of the exhaust and locate the catalytic converter (use the vehicle manual as a guide if you have to). See if the device is bolted or welded to the rest of the exhaust system. If it's welded, you need a sawzall or a similar tool and a welding machine in order to replace it. If you don't have access to these tools and don't have the advanced skills to handle these, it would be best to leave the job to a certified mechanic.

Removing the old catalytic converter

Pull out the oxygen sensor from the catalytic converter. Some catalytic converters are even equipped with more than one oxygen sensor. Use an oxygen sensor socket and ratchet wrench to remove it.

For the bolt-in catalytic converter

Apply some penetrating oil to the bolts to make it easier to undo them. Leave this on for several minutes before you loosen the bolts using a right-sized wrench. Start at the back end first and then at the front. Remove the rear bolts first before those on the front. Once all the bolts are removed, you can now detach the converter. Support the exhaust once the converter has been pulled out.

For the welded-in catalytic converter

Cut the converter out of the pipes where it's connected with a sawzall or a similar tool. The cut should be along or near the weld lines. If the converter can't be moved easily, you'll need a little help with the hammer to take this out its place. However, be careful not ruin any part with just a gentle strike or blow.

Installing the new catalytic converter

Note: Check the installation instructions or guide on the new catalytic converter. Installation or the steps for replacement will vary depending on the catalytic converter.

For the bolt-in catalytic converter

Slide in the gaskets that come with the new converter. Bolt-in converters may come with gaskets that sit within the pipes that are connected to the converter. Install these gaskets according to manufacturer instructions.

Set the new converter in place. Line it up and hold it in proper position. Make sure that this is in the right direction and it's facing the right side. Once properly placed, tighten down the bolts with a right-sized wrench. Start at the front and then at the back.

For the welded-in catalytic converter

Weld the converter using a welding machine (MIG welder, e.g.). Welding should be done by a skilled or trained welder. As you weld the device, the converter must be connected to the exhaust system pipes at both ends. Each weld should create an air-tight seal. Let each weld to cool properly.

After installing the converter, you can re-attach the oxygen sensor. Screw it back into place. See to it that the wiring is well and intact.

Testing the newly installed catalytic converter

Double-check the attachment to ensure that it's properly installed and connected. The bolts should be tight and there should be no leaks from the exhaust. Test it out. See how the vehicle runs.