Learn how to replace a bad catalytic converter. We are
a team of ASE certified mechanics that have created this service guide to help
you save money by replacing the part yourself or at least see what you are
paying for when having it done at a repair shop.
How Does it Work?
A catalytic converter or cat converter as it is sometimes called is designed
to remove unspent fuel in your cars exhaust system which is produced from the
normal process of the engine running. Unspent fuel will enter the atmosphere
in the form of hydrocarbons which creates air pollution. To reduce unspent fuel
this catalytic converter is fitted to the car's exhaust system just behind the exhaust
manifold. This positioning is used to heat the catalyst material which creates a
thermo reaction to burn the unspent fuel.
Catalytic converter costs can very greatly depending on manufacturer and
configuration. The part alone can cost between $550.00 and $1250.00 (US) and
labor should be between $125.00 and $220.00 (US). There is sometimes a core charge
which will be redeemed when the old cat has been returned to the dealer or parts
How Long Do Catalytic Converter Last?
Typically a catalytic converter will last between 90,000 and 140,000 miles but they can loose
their efficiency sooner if the car is driven aggressively. A cat converter works
best when the car is driven mildly and for long distances. There can be several
symptoms when a catalytic converter goes bad which will very from simply not
passing a smog test to the
having low power.
Watch the Video!
There are typically two types of replacements. A signal catalytic converter replacement and a
Y pipe style which is incorporated into the exhaust head pipe. The video below
shows a signal cat replacement while further down we show a video on a Y pipe
style. After watching the video continue down our guide to pick up on addition
information which is updated regularly.
Remove the Catalytic Converter: Before removing the catalytic
converter its a good idea to spray WD40 into the mounts nuts and bolts to help
penetrate the rust which typical is present on the exhaust systems. Locate and
spray the front exhaust flange and tail pipe flange connection bolts.
While the anti-rust liquid is settling in, locate and disconnect the oxygen sensor electrical connectors that are
mounted on the catalytic converter and sometimes in the head pipe. These
connectors will have safety clips that will need to be pushed inward before they
will come undone while gently pulling to get them apart.
Follow the wiring and removing the oxygen sensor wiring from their holders
and safely set them out of the way so they don't get damaged while removing the
Most catalytic converter's have heat shields designed to keep heat away from the vehicle's undercarriage. To gain access to
some of the mounting bolts these shields may need to be removed. After the anti rust liquid has sat for
a while use a 14mm, 15mm or 17mm wrench of socket to remove the bolts by turning them
counterclockwise. You may need an extension to help with the removal, a
universal socket also helps. These nuts or bolts can be tight and a little rusty so be
ready to put some force on them.
Continue by removing the exhaust pipe coupler mounting
bolts using a 15mm or 17mm wrench or socket at the rear of the catalytic converter.
Each application will very and some may need to be cut using a hacksaw and then
welded up once the new catalytic converter has been installed. They also make a
exhaust pipe repair kit that is basically a wide clamp which you can get from
Amazon or the local parts store to put the pipes back together.
Once loose use a pry bar to further loosen the clamps to aid in the removal process. This will help create clearance between the clamp
and exhaust pipe.
Once the rear exhaust mount has been removed use a plastic or rubber hammer to separate the muffler from the catalytic converter
Grasp the catalytic converter with both hands and maneuver it out from the
exhaust manifold and rear exhaust system. Some catalytic converter's have a heat
shield which can be sharp so be carful not to cut yourself.
Remove the Oxygen Sensors: Some catalytic converters have multiple
oxygen sensors which need to be labeled to avoid confusion when reassembling.
Use tape to identify the position of the sensor so they can be easily installed
into the new catalytic converter. You don't want to get these mixed up because
the wiring connectors are different and will not reconnect to the main wiring
Apply WD40 to each of the sensors to aid in their removal. Once successfully labeled remove all
sensors from the old catalytic converter using a 7/8 or 22mm wrench and turning
them counterclockwise, then set them to the side.
Clean the Gasket Surface: At the exhaust manifold there is a gasket
surface that needs to be free of corrosion, dirt and old gasket material left
behind from the old catalytic converter. Use a gasket scraper and a small wire
brush to the gasket sealing surface this will help the new gasket conform
to the sealing surface which will avoid leaks. Set the new gasket in place
by either letting it hang on the exhaust manifold studs or the head pipe of the converter.
Install the Oxygen Sensors: Install the labeled oxygen sensors onto
the new catalytic converter into their correct positions. Thread the oxygen
sensors by hand to avoid cross threading. It's a good idea to add a small amount of
anti-seize to the mounting threads to aid in the
oxygen sensor removal if replacement is required.
Install the New Catalytic Converter: The new catalytic converter is now ready for installation.
Gently position the catalytic converter back up into the exhaust manifold flange
making sure the gasket is still in position. Guide the flange coupler
that is on the head pipe over the exhaust manifold studs. Some applications will
use bolts instead of nuts, in which case simply align the bolt holes.
Hand thread in the mounting nuts or bolts and but do not tighten. Use a socket
to take up the slack while still leaving them loose. The final tightening will be done after
the rear of the catalytic converter has been put in place and reconnected. If
you tighten these nuts or bolts prematurely it will cause a strain and a
possible leak as the unit will need to be forced into position to connect the
rear of the unit.
Install and tighten the coupler mounting bolts at the rear of the catalytic
converter. This coupler can slide up over the pipe and then be pushed downward onto the rear exhaust pipe. Tighten
these bolts completely and then finish tightening the front of the catalytic
converter flange nuts or bolts. The torque specifications for both are 25 to 30
Reconnect the Oxygen Sensors: Reach up and remove the oxygen sensors connectors from there safe
place and start to reconnect them. Push the connectors together enough to hear a
click which confirms their complete reconnection. Push the wiring into their
plastic holders and out of the way of the exhaust pipe or catalytic converter.
This will help avoid melting the wires which will
cause the check engine light to come on. Reinstall any heat shields and
exhaust system mounts that were removed during the job and you are all set. If
the check engine was set due to the catalytic converter being bad the codes will
need to be cleared.
Watch the Video!
Here is a video on how to replace a catalytic converter on the V6 or V8 engine
that have a "Y" style of set up. For this job the vehicle must be raised
it he air higher in some cases.