Repair 7

Catalytic converters are a vital part of any automotive emission system. These devices use heat to chemically react (catalyze) with harmful emissions like carbon monoxide, nitric oxides and unburnt hydrocarbons and convert them to more inert forms. Theyve been required on all cars sold in the united states since 1975, and have helped to change the landscape of the automotive industry worldwide.

History

Catalytic converters were first developed in the 1950s by Eugene Houdry, a French-American engineer. They first entered production for use on automobiles in 1973, and were legislated as mandatory in 1975. Other industries soon jumped on the green wagon, applying converters to practically anything with an engine, including forklifts, generators and battleships.

Function

All catalytic converters function on essentially the same principal. The converter housing contains a grid-like substrate that is designed to reach extremely high heat, finishing the combustion process begun by the engine and vaporizing contaminants. Many converters store excess oxygen from the catalytic process, using it to speed up the reaction under high-stress conditions. The inside of some converters can reach over 1,000 degrees under normal operation, and significantly more under meltdown conditions.

Types

Older converters used a lead pellet design to capture heat, forcing the exhaust to flow through and around the metal balls, which were trapped in a containing matrix. More modern converters use honeycomb-shaped matrices of platinum-palladium alloy, coated with a wash-coat of silica and alumina, which helps increase efficiency. The newest converters use a ceramic honeycomb which lasts longer, is more efficient and contains little or no precious and expensive platinum alloy.

Converter Drawbacks

Older catalytic converters were very heavy and restrictive, costing precious horsepower in the deficit days of the 70s and reducing fuel mileage by as much as 10 percent. The newest high-flow honeycomb designs, however, flow significantly better than lead-pellet types. Converters often produce harmful emissions of their own: hydrogen sulfide and ammonia are the most common, but some also produce the organic toxin dioxin.

Cash for Cats

Catalytic converter theft is rampant in some areas, since older units contain great quantities of the aforementioned precious metals. A typical catalytic converter contains over $200 worth of platinum, palladium and rhodium. But dont break out the reciprocating saw and retirement plan just yet; according to the EPA, the cost to extract these precious metals from used converters makes recycling them for the platinum only slightly more economical than simply ining more.

The catalytic converter regulates and reduces pollutants within the vehicles exhaust. Vehicles are required by law to have them, so you need to replace them if they are no longer working. On a current Chevy Silverado, the catalytic converters are welded to the front exhaust pipe assembly, so replacing a catalytic converter means replacing the entire front exhaust pipe assembly. This process can differ on older models (specifically ones made prior to 2007), so check with your mechanic.

Instructions

1

Raise the truck and support it on jack stands.

2

Disconnect the electrical connectors for the converters upstream and downstream oxygen sensors. Unscrew and remove the sensors using an oxygen sensor socket.

3

Unscrew and remove the three nuts that are on the upper-left and right flanges connecting the front exhaust pipe assembly to the exhaust manifolds flanges using a wrench. Remove the nuts for the rear flange of the front exhaust and remove the front exhaust pipe.

4

Install new flange gaskets onto the three mounting flanges of the replacement exhaust pipe (which will include the replacement converters).

5

Coat the threads on the mounting nuts and bolts with anti-seize compound. This includes the threads on the oxygen sensors.

6

Install the exhaust pipe system and securely tighten the nuts and bolts for the three flanges connecting it to the manifold and the rest of the exhaust system.

7

Connect the upstream and downstream oxygen sensors to the front exhaust pipe using the same socket as before.

Burns Unburned Exhaust Gases

The main purpose of an automotive catalytic converter is to burn unburned engine exhaust gases exiting a cars engine. Engine combustion is not an exact science; theore, during normal engine operation, there are small bits of unburned fuel that get pushed out a cars engine during the exhaust stroke of an engine cycle. When this happens, the unburned fuel flows down a cars exhaust pipe on its way to the car tail pipe, where it would get released into the outside air. A catalytic converter, which looks almost identical to a car muffler in shape and size, is filled with small charcoal-like pellets called catalyst which become super-heated as exhaust gas flows pas them. These super-heated pellets react with the unburned gas molecules in a cars exhaust and simply reburn them, turning them into simple water and carbon dioxide molecules.

Makes Unleaded Gasoline Use Mandatory

Cars equipped with catalytic converters must be operated with unleaded gasoline only. Unleaded gasoline, due to its absence of lead, is a much cleaner and environmentally-friendly fuel than leaded gasoline. Lead is toxic to the environment and toxic to human health. The catalyst material used in catalytic converters, usually consisting of small platinum-coated charcoal pellets, are highly-sensitive to lead-based gasoline and would quickly be ruined and rendered ineffective if exposed to leaded gas. Theore, catalytic converter-equipped cars are designed to run on unleaded gasoline only, a gasoline that is inherently cleaner and less toxic than leaded gasolines. So, not only do catalytic converters help to make engine exhaust gases cleaner, they automatically require the use of cleaner gasoline to begin with.

Retards Exhaust Gas Flow

Catalytic converters create a small amount of back pressure within a cars engine. This is due to the constrictive effects that a catalytic converter has on exiting engine exhaust gases; the charcoal pellets combined with the small exhaust tubing within a catalytic converter slows down the speed at which exhaust gases exit an engine. Due to this slowing down of engine exhaust gas flow, a cars engine has slightly more time in which to adequately combust, or burn, its air/fuel mixture, a process that results in slightly cleaner exiting engine exhaust gases.

Catalytic converters use various types of metals to scrub pollutants from a vehicles exhaust before it leaves the tail pipe. Generally, catalytic converters will last the life of a Mercedes 560SL, but some factors, such as using unleaded gasoline or too many fuel additives, can contribute to the premature failure of the catalytic converter.

Loss of Power

A stopped up catalytic converter will cause a sudden loss of power in a Mercedes 560SL. Sometimes catalytic converters break down slowly over time, causing a gradual loss in power, which may not be noticeable to some drivers. If your Mercedes will not accelerate, even if you stomp on the accelerator pedal, have a mechanic take a look at the catalytic converter to see if it is stopped up. If this is the case, the catalytic converter will need to be replaced.

Drop in Fuel Economy

Measure the gas mileage your car is getting, especially since a sudden drop in fuel economy can indicate mechanical problems. A stopped up catalytic converter will cause a significant drop in fuel economy, more than two or three miles per gallon difference.

Engine Problems

A clogged catalytic converter will also cause operating problems with your Mercedes engine. Besides the loss in power, a stopped up catalytic converter can inhibit how quickly a vehicle travels, making it top out at a low speed like an electronic speed governor. The clogged catalytic converter will cause increased back pressure in the exhaust system, which will choke the engine as exhaust gases cannot leave as quickly as they should. If your car runs for a few minutes then stalls out, if you can hear a whistling sound or your cars engine seems to be struggling during acceleration, take a look at the catalytic converter as the potential cause.

Smell

If your 560SLs tailpipe is spewing out a smell similar to rotting eggs, there is a high chance that the catalytic converter is partially clogged. The broken down elements of the catalytic converter emit this rancid smell, which is very noticeable.

Catalytic converters neutralize harmful gases in a vehicles exhaust. The catalytic converters on the 2002 Ford Mustang are integrated into the exhaust pipe assembly that runs from the collector to the rear pipe. This section of pipe can be replaced in under an hour with the proper tools and a little elbow grease. While it is easiest to perform this with the Mustang on a lift, you can remove this assembly in your garage with a floor jack and jack stands.

Instructions

1

Chock the rear wheels and slide the floor jack under the front of the Mustang. Jack the car up and place the jack stands under the front frame on both sides, away from the exhaust work.

2

Climb underneath the Mustang and secure the left, rear exhaust pipe, containing the muffler, to the frame with the wire coat hanger. Repeat this on the right side.

3

Wrap the last wire hanger around catalytic converter pipe assembly and hang it from the frame as well.

4

Use the socket set to unbolt the rear flange on the catalytic converter pipe assembly.

5

Move forward and unbolt the forward flange on the catalytic converter pipe.

6

Remove the coat hanger holding the rear section of the pipe to the frame and move the entire catalytic converter pipe assembly out from under the Mustang.

7

Install the replacement catalytic converter assembly in reverse of how you removed the old one. Dont forget to remove the coat hangers when done.

Most motorists view catalytic converters as a mixed blessing. They improve air quality by reducing tailpipe emissions, but they also add back-pressure that handicaps performance. This was the case with early pellet-based catalytic converters, but according to tests in "Import Tuner" magazines October 2006 issue, the monolith "brick" ones we use today have a minimal effect on the engine. Since replacing a bad catalytic converter can cost thousands, here are some ways to buy time.

Clean it

If your converter has a carbon buildup or mild oil fouling, try cleaning it before replacing it. Catalytic converter cleaner/deodorizers are available for $13 to $25, and you can add them to your gas. As you drive, the cleaner removes deposits from the converter and the rest of the engine. If this doesnt solve the problem, your converter might be clogged with sulfur from your fuel and phosphorous from your oil. Scientists at Madrids Institute of Catalysis and Petrochemistry have discovered that diluted citric acid can remove these deposits without affecting your converters platinum. Just soak the catalytic converter in a citric acid solution for six hours; and if it doesnt have other problems, itll be as good as new.

Stop the Rattles

When a catalytic converter begins to fail, its monolith substrate filling cracks, and the pieces rattle. Since the substrate absorbs the toxic exhaust gases, the longer you keep it from coming apart the better. The best way to do this is by using a mechanics stethoscope to find out where the loose pieces are. Drill a small hole at each location and put a large drywall screw in it. The screws will hold the loose pieces in place and delay the inevitable replacement of your converter. Its also possible for your catalytic converters heat shield to start rattling. You can fix the problem by screwing hose clamps together to make a giant hose clamp that fits around the heat shield. Just crank it down until its tight enough to keep the shield from moving.

Gut it

When all else fails, you have one more option before replacing the catalytic converter. You should only choose this option when the monolith substrate filling of your converter is too cracked to repair or too fouled to clean out. At this stage you can only unclog the converter by removing its substrate filling. Gutting the converters contents will relieve the back-pressure in the exhaust and make your car drivable until you get a new converter. Start by unbolting the intermediate pipe from the back of the converter to expose its interior. Insert a big crowbar into the converter and start banging it around. Hit the crowbar with a hammer from time to time to speed up the process. You can check your progress with a flashlight and use a shop vac to suck out substrate pieces. You can also idle the car a few times to blow out stubborn chunks. After a final pass with the shop vac, you can reconnect the intermediate pipe and get back on the road. Always use a mask and creeper for this job to avoid contact with the substrate.

A catalytic converter greatly reduces the amount of emissions that your vehicle produces. However, when this part has gone bad it can mean trouble for your vehicle as well as the environment. Certain clues will help you determine whether your catalytic converter is failing.

Driveability

Your ability to drive your vehicle normally will be affected if the catalytic converter is bad. The speed and the power of a vehicle will fall below their normal performance levels. If your vehicle starts to have trouble with stalling, this could be a sign of bad catalytic converter.

Emissions

A rise in vehicle hydrocarbons and carbon monoxide emissions is a sure sign that a catalytic converter has gone bad. An exhaust analyzer, which costs $3,000 to $5,000, can inform you whether the converter is bad by reading the emissions levels as they exit the exhaust pipe.

Exhaust

The color of the smoke coming from your exhaust is another way to determine whether a catalytic converter is bad. Blue smoke indicates that the converter might be contaminated with phosphorus, which is found in motor oil. White smoke usually indicates that coolant is leaking internally.

Your catalytic converter is the part of your vehicles exhaust system designed to reduce the amount of toxic emissions of gases that leave your car and enter into the environment. Because of increasing concerns about pollution, catalytic converters are among the most heavily legally regulated parts of your vehicle. It is illegal to modify or alter your catalytic converter in any way, so the only way to legally repair your clogged catalytic converter is to have an exhaust shop or certified mechanic replace it.

Instructions

1

Take your car to mechanics shop that specializes in exhaust problems and repairs. Have a certified professional mechanic evaluate your vehicles problem and determine definitively that its the catalytic converter causing it. The mechanic is not allowed to replace the catalytic converter unless he is able to thoroughly document a problem with it. No individual or mechanic is legally allowed to tamper with the converters mechanical workings in any way, theore the converter must be replaced. If your car has failed emissions test or state inspection, you should keep the documentation related to that as proof that there is a problem with the catalytic converter.

2

Determine if your car is still covered by the federally mandated catalytic converter warranty. This means if your car is less than eight years old or has fewer than 80,000 miles on it, the original manufacturer is responsible for replacing the catalytic converter free of cost. In this case, you should take all the documentation of the problem to your local dealers parts and service department and have them replace the catalytic converter free of charge under the warranty.

3

Have mechanic replace catalytic converter with an identical model. Youre not allowed to alter the design or change models from the original manufacturer installed catalytic converter. Once the converter has been installed, make sure your mechanic correctly fills out and submits the federally required warranty card. Keep all documentation for catalytic converter in case a problem arises later during emissions testing.

Dealing with the catalytic converter on a vehicle tends to be time-consuming. Various federal and state laws mandate how these emission controllers must be installed, modified and removed and disposed. In Michigan, however, no specific laws deal with the disposal of catalytic converters, meaning you are free to dispose of it more or less how you please. The best and most profitable way is to recycle it.

Instructions

1

Locate a scrap yard in your area of Michigan that accepts used catalytic converters. The USA Catalytic Converter Directory provides a list of Michigan recycling and metal companies that recycle catalytic converters (See resources).

2

Take your catalytic converter to the recycling center or scrap yard you have chosen.

3

Request the scrap yard or recycling center to weigh the converter and assess its value, then accept payment for it. You will probably only receive a couple of dollars for it, but it will be properly recycled and diverted from landfills.

A catalytic converter is an exhaust emissions device used to lower a vehicles exhaust emissions output. Similar in size and shape to an exhaust muffler, a catalytic converter is attached directly to a vehicles exhaust system. What follows is a brief description outlining the main purposes of catalytic converter use.

Burn Unbruned Exhaust Gases

The main function of a catalytic converter is to burn unburned exhaust gases that exit a vehicles engine. By burning these unburned exhaust gases, a catalytic converter lowers the emissions output of a vehicles exhaust.

Impede Normal Exhaust Flow

A catalytic converter creates exhaust system impedance, which causes the exhaust exiting a vehicles engine to slow down, a process that gives the catalytic converter more time to act upon the exhaust gases.

Reduce Hydrocarbon Exhaust Emissions

Hydrocarbon emissions, which are created when air and gas is burned inside of a vehicle engine, are significantly reduced by the burning action of a catalytic converter.

Mandate Unleaded Gasoline Use

All vehicles equipped with catalytic converters require the use of unleaded gasoline, which is a cleaner-burning type of gasoline that results in lower exhaust emissions. Leaded gasolines and/or racing gasolines are highly damaging to a catalytic converter and cannot be used in cars equipped with one.

Reduce Carbon Monoxide Emissions

Carbon monoxide exhaust emissions are significantly reduced by the burning actions of a catalytic converter. Carbon monoxide gases are natural by-products of engine combustion, and catalytic converters help to lower these emissions by re-burning exiting engine exhaust gases.

Catalytic converters, important to your vehicles emissions, clean exhaust before it enters the atmosphere. A bad catalytic converter can turn on your "Check Engine" light and lead to ensuing engine problems and power loss in your Camry.

Late-Model Camrys

Camrys made after the year 2000 will likely have two catalytic converters whether they have a four- or six-cylinder engine. Typically, the front converter is much less expensive to replace. Earlier-model Camrys from the 1990s and before may have only one converter, depending on the model.

California Camrys

Califonria has particularly strict emission laws. Camrys sold and driven in California will definitely have two converters.

Further Considerations

If still unsure about how many catalytic converters your Camry has, a mechanic can look under the car and quickly tell you. If your "Check Engine" light has turned on, have a mechanic plug the car into a diagnostic machine to determine which, if either, converter has begun to fail and diagnose the underlying engine problem.

The Madza RX-7 is a two-seater sports car made by Mazda. The RX-7 is unique in that, unlike almost every other car on the market, the RX-7 uses a rotary engine instead of a piston engine to make its power. This is practically unheard of in the automotive world. The 2-rotor engine, also called a Wankel engine after its inventor, Felix Wankel, has up to 40% fewer parts than a piston engine and is able to create a tremendous amount of power with a lightweight, simple design. With that said, the Mazda RX-7 does have a traditional exhaust system, which includes a catalytic converter. Over time, as in piston engines, these converters eventually burn out and need to be replaced.

Instructions

1

Jack up the front of the RX-7. Place the jack under the front jack point of the RX-7. This is located behind radiator.

2

Place jack stands under the frame of the vehicle and lower the RX-7 onto the jack stands.

3

Unplug the electrical wiring running to the O2 sensor on the catalytic converter.

4

Remove the catalytic converter to exhaust tubing bolts with a socket wrench.

5

Remove the catalytic converter to manifold bolts with a socket wrench.

6

Separate the catalytic converter from both sides of the exhaust. You may need to use a flat head screwdriver to pry the mating surfaces apart.

Replacing the catalytic converter on a 2001 Honda Odyssey will save money and can be done without special tools. The retaining nuts on the converter may be seized from temperatures they endure over time, so plan to spray them for several days with a good penetrating oil to help loosen them. A replacement converter for the Honda model is available from Honda dealers or larger auto parts stores.

Instructions

1

Raise the front of the Odyssey with a jack and position a set of jack stands under the front suspension. Lower the jack, setting the van on the jack stands. Be sure the van is stable before sliding under it just behind the front tires.

2

Locate the catalytic converter in the exhaust system; it should be just behind the head pipe. Look for the heat shields that wrap around the top and bottom of the converter and the two mounting bolts that hold the shields in place on either side. Remove the bolts with a socket and ratchet and remove the heat shields from the converter.

3

Locate the three mounting studs on each end of the converter and remove the nuts from the studs with a wrench. Afterward, pull the rear pipe assembly back from the converter until it clears the studs. This allows you to push the pipe off to the side and out of the way.

4

Pull the converter back from the head pipe until the studs clear the mounting flange. Then lower the converter to the ground. Two brass gaskets are used to seal the converter to the flanges; make sure they come out as well.

5

Position a new converter under the van and raise it into position. Align the studs with the front flange and slide them together loosely. Then slide the rear pipe onto the studs at the back of the converter.

6

Tighten the retaining nuts onto all the studs a few turns just to hold the converter in place. Insert a new brass gasket into gap between the catalytic converter and the flange on each end. Torque all six retaining nuts to 25 pound-feet with a torque wrench and socket.

7

Install the heat shields around the new converter, install the retaining bolts and tighten them with a socket and ratchet. Raise the front of the van off the jack stands with a jack and remove the jack stands. Lower the van onto the tires and remove the jack from under it.

Catalytic Converter as Afterburner

The sole job of a catalytic converter is to reheat already-burned exhaust gases from a cars engine. As burned engine fuel, or exhaust, leaves a cars engine, it travels along a cars exhaust system. A catalytic converter is located in the middle portion of the exhaust system--between the engine and the tailpipe. Exhaust gas flows directly into the catalytic converter and is reignited and reburned to reduce emissions.

Catalytic Converter Makeup

The outside of a catalytic converter looks just like a car muffler. It is sort of oblong with an aluminum outer cover. A cars exhaust pipe flows directly into a catalytic converter, which houses a catalyst that is superheated by the flowing exhaust gases and ignites the incoming exhaust gases. This catalyst is usually made up of small pieces of palladin, a heat-reactive element that turns glowing hot when heated.

Reduction of Exhaust Emissions

As exhaust gas exits a catalytic converter and flows toward the cars tailpipe, the vehicle emissions are much lower than they were before entering the catalytic converter. Due to the heating and re-igniting effects of the catalyst elements on the exhaust gases, much of the unburned or improperly burned fuel is burned in the catalytic converter and prevented from exiting the cars tailpipe into the outside air. This greatly reduces vehicle emissions.

Unleaded Gas Only

All cars equipped with catalytic converters require the use of unleaded gas only. The catalyst elements inside a catalytic converter are highly sensitive and can be damaged by gas that contains lead. Catalytic converters were first installed on American cars in 1975, the first year of unleaded gasoline.

The catalytic converter installed on your vehicle is an important component in your vehicles emissions system. These converters generate a large amount of heat, so the underside of the vehicle typically has a heat shield bolted to the body to help dissipate some of that heat. Should this metal heat shield bend or get damaged, then it will rattle against the catalytic converter, which can damage the converter as well as make a horrible noise. To fix the problem, you need to remove the heat shield from the car to either fix the shield or replace it.

Instructions

1

Lift the vehicle using the jack and put it onto a set of jack stands so that you have enough room to fit underneath the vehicle. Let the exhaust cool down if the vehicle has been run recently so that you dont burn yourself.

2

Crawl underneath the vehicle and locate the catalytic converter, which is an oval shaped section of the exhaust tubing located before the muffler on the exhaust system.

3

Unbolt the metal heat shield from around the catalytic converter using an open-end wrench. Pull the metal heat shield out from behind the catalytic converter and then take it out from under the vehicle.

Catalytic converters were first used to scrub pollutants from automobile exhaust systems in the United States in 1975. Today converters are required equipment on most passenger cars and light trucks sold in the U.S., where they have helped reduce vehicle emission pollution by more than 90 percent, according to CatalyticConverter.org. The U.S. Environmental Protection Agency (EPA) enforces emission performance specifications and other requirements for new and reconditioned converters.

Warranties

For new light-duty cars and trucks, converter manufacturers must provide a performance warranty covering repair of converters that fail emission control system tests in two years or 24,000 miles. Repair of major emission system parts is covered for eight years or 80,000 miles. A separate design and defect warranty covers emission control system parts that malfunction during the first two years or 24,000 miles, and major emission system parts in the first eight years or 80,000 miles.

Illegal Tampering

Any modification that reduces the effectiveness of a vehicle emission control system is illegal. Removing catalytic converters, selling or installing less effective replacement converters, or manufacturing converters that do not comply with federal performance specifications are subject to $25,000 penalties per occurrence. Vehicle owners, repair technicians and repair facilities can all be held responsible for violations.

New Replacement Converters

New aftermarket converters can be installed on a wide variety of different vehicles. They must carry a 25,000-mile warranty to meet federal emission performance standards, and a five year or 50,000-mile warranty on the converter end pipes and shell.

Used Replacement Converters

Used, or reconditioned, converters can only be installed on the type of vehicle for which they were originally manufactured. They must meet minimum EPA performance standards at the time of the sale but are not required to carry a warranty.

Catalytic converters are engine exhaust emissions devices installed on vehicles to help reduce the levels of vehicle exhaust emissions. Similar in size and shape to a vehicle exhaust muffler, a catalytic converter is attached directly to a vehicles exhaust system.

Significance

A catalytic converter is an exhaust emissions device installed on vehicle exhaust sytems in order to reduce the levels of engine exhaust emissions, most notably the levels of hydrocarbon emissions. Catalytic converters were first installed on American cars in 1976 in response to growing concerns about vehicle-generated air pollution.

Function

The main function of a catalytic converter is to reduce the amount of exhaust hydrocarbon emissions exiting a cars tail pipe. A catalytic converter is filled with a thin, porous material called catalyst, which is designed to react with and burn flowing engine exhaust gases, thereby re-burning these gases, which leads to a reduction in hydrocarbon emissions.

Fun Fact

Vehicles equipped with catalytic converters require the use of unleaded gasoline. Leaded gasoline damages and destroys the catalyst element located inside a catalytic converter, which renders the converter useless as an exhaust emissions lowering device.

Geography

A catalytic converter is bolted directly to a vehicles exhaust system at a point roughly halfway between the vehicle exhaust manifold and the tail pipe. Located in close proximity to the vehicle muffler on a cars underside, the catalytic converter is normally installed at a point almost directly underneath the drivers side area of a car.

Benefits

Catalytic converter use results in a marked decrease in vehicle exhaust hydrocarbon emissions, emissions that are created when gasoline is burned inside a vehicles engine. Widespread catalytic converter use has significantly reduced the levels of vehicle exhaust emissions since converters became standard vehicle equipment in 1976.

In 1953, Ford slightly redesigned its F-series pickups and in the process revamped the names of the F-series trucks; the F-1, F-2 and F-3 became the F-100, F-250 and F-350, respectively. The 2006 Ford F-250 had three engines available, but it came standard with a 300-horsepower, 5.4-liter V-8 engine. This engine, as with all modern automotive engines in the U.S., came fitted with a catalytic converter, which converts harmful gases in the exhaust to harmless ones. Replacing the catalytic converter on the base level 2006 F-250 is a straightforward task

Instructions

Removal

1

Allow the vehicle to sit until the engine is cool to the touch, then allow it to sit for an additional hour to allow the catalytic converter to cool, as the converter typically is significantly hotter than the rest of the exhaust and retains heat more effectively.

2

Kick wheel chocks behind the rear wheels and raise the front of the F-250 with a floor jack. Slide jack stands under the frame rails and lower the vehicle onto the jack stands.

3

Crawl under the middle of the truck until you have a clear view of the catalytic converter.

4

Remove the four catalytic converter-to-Y-pipe nuts, using a ratchet and socket. If the nuts are seized, spray penetrating oil onto them and wait for the amount of time the oils instructions prescribe.

5

Loosen the clamp securing the intermediate pipe to the catalytic converter pipe using a ratchet and socket.

6

Trace the wiring for the catalyst monitor, the oxygen sensor on the catalytic converter, upward until you reach where its harness connects to the F-250s harness. Unplug the sensors harness from the F-250s harness.

7

Press the rubber catalytic converter hanger from the catalytic converters bracket. Press the converter rearward until the converter-to-Y-pipe studs are free from the Y-pipe, and lower the front part of the catalytic converter. Slide the catalytic converters pipe from the intermediate pipe and remove the converter from the truck.

8

Remove the catalyst monitor, the oxygen sensor on the catalytic converter, using a ratchet and oxygen sensor socket.

Installation

9

Apply a thin coating of an anti-seize compound to the catalyst monitors threads and hand-tighten the monitor into the new catalytic converter. Tighten the catalyst monitor to 34 foot-pounds using a torque wrench and oxygen sensor socket.

10

Scrub the mating surface on the Y-pipe with a wire brush. Guide a new catalytic converter-to-Y-pipe gasket onto the mating surface on the catalytic converter. Clean the mating surface on the inside of the intermediate pipe with emery cloth.

11

Lift the catalytic converter into place and press its bracket through the hole in the converters rubber hanger. Guide the convertor-to-Y-pipe studs through the bolt holes in the Y-pipe. Hand-tighten the four converter-to-Y-pipe nuts onto the studs.

12

Guide the rearmost pipe on the catalytic converter into the intermediate pipe. Move the intermediate pipe-to-catalytic converter pipe clamp so its within 0.15 inches of the end of the intermediate pipe and the bolt is at a 90-degree angle relative to the slots cut in the end of the pipe.

13

Tighten the convertor-to-Y-pipe nuts to 30 foot-pounds using a ratchet and socket, and tighten the intermediate pipe-to-catalytic converter pipe clamp to 41 foot-pounds.

Replacing the catalytic converter on the Chevy Trailblazer is a great job to tackle at home. The converter bolts in place between the front exhaust pipe and the muffler, making it easy to get to and change. The converter is a little heavy, so be careful when you remove the bolts to make sure that it does not fall on you. Replacement converters are available through your Chevy dealer, as well as from most major auto-parts stores.

Instructions

1

Raise the front of your Trailblazer with a jack and support it on a set of jack stands positioned under the frame rails. Slide under the passengers side of the vehicle and locate the catalytic converter in the exhaust pipe between the engine and the muffler.

2

Locate the oxygen sensor in the converter. Follow the wire from the sensor to the wire harness connector and disconnect it from the harness. Place an oxygen-sensor socket on the sensor and remove it from the converter with a ratchet. Set it aside.

3

Loosen the two bolts on the mounting flange between the rear of the catalytic converter and the exhaust pipe using a socket and ratchet. Remove the bolts from the flange and pull the pipe aaway from the converter. Push the pipe aside.

4

Move to the front of the converter and remove the two mounting bolts between the flange and the front pipe with a wrench. Pull the converter out and remove it from under the truck.

5

Position a new converter in place under the truck. Lift the converter up into place and install the retaining bolts from the front pipe to the front flange on the converter. Leave them loose for now.

6

Position the rear pipe up against the rear flange and install the rear mounting bolts loosely. Tighten the front bolts by torquing them to 33 ft.-lbs., then tighten the rear bolts to 33 ft.-lbs. as well.

7

Install the oxygen sensor from the old converter into the new converter and tighten it with a oxygen sensor socket and ratchet. Connect the wiring harness connector from the oxygen sensor to the wiring harness connector on the truck. Push the connectors together until they lock in place.

8

Raise the front of the truck off the jack stands with a jack. Remove the stands from under the truck, lower the jack and remove it from under the truck.