Your cars catalytic converter is designed to burn extra gasoline fumes that make it through your engines combustion chamber to reduce your cars emissions.
The converter can be thought of as a filter and small furnace to burn these vapors. Its internal parts are made of titanium and its outer shell is made of heat resistant steel just like the rest of your exhaust system.
Thinking of the Catalytic Converter as a filter will let you understand how problems will eventually occur. We say eventually because deposits in the web mesh will build up over time and finally clog the converter. This will require replacement.
WARNING! Before you begin working near your Catalytic Converter you should know that it can reach temperatures that are 3 times as hot as your kitchen oven. The converter will also hold the heat for some time so it is important to not touch the housing even with heavy gloves. If you need to work on the cat or its sensor you should do so when the vehicle is cold.
Diagnosing your Catalytic Converter
The first sign of a fading converter will be reduced performance. Unfortunately these symptoms can also occur from maintenance being required in your fuel and ignition system.
Things to look for:
- Loss of power
- Stalling
- Hesitation and sputtering
- Starting Trouble or no start
Some people say that when the Cat goes bad you will also smell a rotten egg smell. This is possible but does not always prove to be true.
Sensors And Computers
New cars with a ODB-2 computer system will most likely have a sensor installed behind the Catalytic Converter to test for burn emissions. If your car has such a sensor you can use a trouble code analyzer to read for any special codes indicating a bad Cat.
A Code Scanner can be purchased for about $75 to read fault codes that your computer stores. Better scanners can be purchased that will read the codes live while your engine runs or while on a test drive.
The Scanner is hooked to a service port under your dash.
If you do not have access to a scanner your local parts supplier may provide access to one for free or you can take your car to most local repair shops.
ODB-2 Computers are found on most 1996 or newer vehicles. ODB1 Computers do not usually have the sensor for the Catalytic Converter. Even Older vehicles with Computer Systems will require specific scanners and like ODB1 Models will not normally have a Cat Sensor.
Even though your vehicle may not have a sensor on its cat a code may indicate that you should inspect the Cat as part of the diagnostic steps to repair a found problem.
Visual Inspection
Unfortunately there is no real easy way to inspect your Catalytic Converter.
If you can remove the part and it is a straight pipe you can try shining a light through one end. If the there is no lite visible through the converter then you know it is clogged and requires replacement.
Converter Test Pipes are also available to allow you to run the vehicle without the converter to test if it is clogged.
In all honesty these test pipes are really used by people that want to race on the street and remove their cat for a few days. At a price of $100 on average a mockup pipe will be much cheaper if you can get hold of some flanges at a junk yard before they sell the converter for its titanium salvage value.
Replacing Your Catalytic Converter
There are two different types of Catalytic Converters that you can purchase.
The first would be an OEM replacement that is a perfect fit to your vehicle. It will come with the appropriate flanges required to bolt directly into your exhaust system in with only a wrench and other hand or air tools.
Generic Catalytic Converters can fit a number of different models of vehicles but they are appropriate for your vehicle based on size, shape and the volume of exhaust fumes that it can process.
Generic Cats can cost 1/3 the price of an OEM Direct Replacement but they do not come with flanges or they will come with an adjustable flange pipe that will require welding.
Most shops that work on exhaust systems as a primary business will use generic parts in this way they can service a wide range of vehicles quickly and they will not have to order parts or stock them in massive parts rooms.
If you are taking your car to a shop then ask them to use a generic Catalytic Converter to save money and use the old pipes with your flanges.
If you are in California and depending on the age of your vehicle you will need a CARB compliant Converter which basically just costs more.
Performing The Work Yourself
Honestly working on an older exhaust is probably one of the worst jobs you can do but there are times when performing the work yourself is something that you can accomplish.
You should think seriously about the lifetime warranties available from a national chain along vs the price you will save. If the difference is enough to make the job worth you while then OEM Perfect Fit Parts are your best choice.
Generic parts can be installed at home but you will need to weld the connections or have them welded at your local shop. If you use clamps to hold your work in place until you can get to the shop you want to make sure that you do not deform the pipes or welding them will be difficult.
Before you get started you will need Safety Goggles not just Glasses that can allow chips of rust to get to your eyes from the sides. THIS IS A STEP YOU DO NOT WANT TO SKIP.
Muffler shops have a dirty trick that you should watch for.
If you are removing clamps or flange bolts make sure that the person that installed the previous system didn’t pass the torch across the threads of the bolts. Some shops say they do this so the system will not fall apart if a nut would get lose but for that to happen it would require more then one to become lose.
If you see damaged threads then you will need to use a reciprocating saw with a fine tooth metal cutting blade to cut away the damage. You can cut as close to the nut as you want because you will be replacing the bolt with a new one.
Removing and replacing the nuts should be performed with an impact wrench.
If you can not back a nut off then try tightening it for a second or two to break the rust weld and then reversing to remove it.
If your system was held in place with clamps then you may need to cut the pipes apart at the crushed union or use a impact hammer with a chisel attachment to cut the pipe off. Cutoff tools can be used but the amount of cutting will make the job long and difficult.
Once all of the pipes are lose you can remove the hangers that hold your system in place.
Replacing your exhaust parts is the reverse of the removal process.
If you are mounting new parts to old then make sure the flanges on the old parts are free of rust.
Install your gaskets where appropriate and connect the pieces loosely until you can get your hangers in place and make sure everything is in the right position.
Once all your clearances are checked then tighten your flange bolts with an impact hammer.
When your system is in place you will need to test drive the vehicle to make sure the hanger system is working correctly and not causing noise.
To make sure your system is tight you can use a rag to cover the exhaust tip or end of your muffler and listen for leaks that sound like steam escaping.
Sensors
If your catalytic converter has a sensor then it is probably best to replace it. Removing them can often destroy the sensor since it is likely to be well rust welded to the part.
QUICK FIX
If your cat is clogged then you can purchase a straight piece of pipe or some flex exhaust pipe at your local store and make a straight through pipe after you cut the center of the cat off. Only drive your vehicle for a very short distance as this may make your engine perform extremely poor if your sensor is not hooked up.
Some people also suggest hammering a metal bar or pipe through the cat. This is possible but be careful while doing it.
Generic At Home
If you are going to install a weld required replacement part at home and have transportation then install the part without clamping it and mark the parts well with whiteout or a black sharpy pen and then remove it and bring it to a shop for welding.
Straight lines across the tubes will show where the pipes should line up so your flanges will align after welding.
Only use your old pipes if they are in excellent condition.
Some Generic Cats will come with new pipes and only require one seam to be welded to fit for length.