Description & Operation
The catalytic converter is a muffler-like container built into the exhaust system. The catalyst element consists of individual pellets or a honeycomb monolithic substrate coated with a noble metal such as platinum, palladium, rhodium or a combination. When the exhaust gases come into contact with the catalyst, it changes residual HC, CO and NOx in the exhaust gas into CO 2 , H 2 O and N, before the exhaust gas is discharged into the atmosphere.
There are basically two types of exhaust systems. One is the flange type where the component ends are attached with bolts and a gasket in-between. The other exhaust system is the slip joint type. These components slip into one another using clamps to retain them together.
Before removing any component of the exhaust system, ALWAYS squirt a liquid rust dissolving agent onto the fasteners for ease of removal. A lot of knuckle skin will be saved by following this rule. It may even be wise to spray the fasteners and allow them to sit overnight.
Before removing any component on a flange type system, ALWAYS squirt a liquid rust dissolving agent onto the fasteners for ease of removal. Start by unbolting the exhaust piece at both ends (if required). When unbolting the headpipe from the manifold, make sure that the bolts are free before trying to remove them. if you snap a stud in the exhaust manifold, the stud will have to be removed with a bolt extractor, which often means removal of the manifold itself. Next, disconnect the component from the mounting; slight twisting and turning may be required to remove the component completely from the vehicle. You may need to tap on the component with a rubber mallet to loosen the component. If all else fails, use a hacksaw to separate the parts. An oxy-acetylene cutting torch may be faster but the sparks are DANGEROUS near the fuel tank, and at the very least, accidents could happen, resulting in damage to the under-car parts, not to mention yourself.
When inspecting or replacing exhaust system components, make sure there is adequate clearance from all points on the underbody to prevent overheating of the floor pan and possible damage to the passenger compartment insulation and trim materials.
Check the complete exhaust system and nearby body areas and rear compartment lid for broken, damaged, missing or mis-positioned parts, open seams, holes, loose connections or other deterioration which could permit fumes to seep into the rear compartment or passenger compartment. Dust or water in the rear compartment may be an indication of a problem in one of these areas. Any faulty area should be corrected immediately. To help insure continued integrity, the exhaust system pipe rearward of the muffler must be replaced whenever a new muffler is installed.
Your GM W-Body vehicle will have one of several types of exhaust systems. On single exhaust systems, for some engines, the entire exhaust system (comprised of a resonator, an exhaust pipe, a muffler and a tailpipe) is serviced as one pre-welded part. Some components may be available in the aftermarket but that will require cutting the one piece system to install the parts.
Other W-Body vehicles may use a dual exhaust system serviced as five different components, clamped together. Always replace the catalytic converter gasket at the flanged joint between the exhaust system and the three-way catalytic converter whenever this joint is disturbed. Never reuse a catalytic converter gasket.
Various types of hangers are used to support exhaust systems. These include conventional rubber straps, rubber rings and rubber blocks. The installation of exhaust system hangers is very important as improperly installed hangers can cause annoying vibrations which can be difficult to diagnose.
When servicing a welded connection, it should be cut and the new connection clamped when installing replacement parts. GM recommends you coat slip joints with exhaust system sealer before assembling and that you use new nuts when assembling components. Always wire brush clean the manifold stud threads with a wire brush before installing new nuts.
The exhaust system (including the catalytic converter heat shield) must be free of leaks, binding, grounding (touching a body or suspension component) and excessive vibration. These conditions may occur is any of the following are loose or damaged: flange bolts or flange nuts, heat shield, brackets, pipes, and mis-aligned or defective components. Inspect for cracks on and around the seals and gaskets, exhaust hanger insulators, around the converter, exhaust pipe and tailpipe. Inspect for stripped bolt threads, corroded fasteners and broken welds. If any component is severely rusted or rusted through, it should be replaced.
Your vehicle must be raised and supported safely to inspect the exhaust system properly. By placing 4 safety stands under the vehicle for support should provide enough room for you to slide under the vehicle and inspect the system completely. Start the inspection at the exhaust manifold or turbocharger pipe where the header pipe is attached and work your way to the back of the vehicle. On dual exhaust systems, remember to inspect both sides of the vehicle. Check the complete exhaust system for open seams, holes loose connections, or other deterioration which could permit exhaust fumes to seep into the passenger compartment. Inspect all mounting brackets and hangers for deterioration, some models may have rubber O-rings that can be overstretched and non-supportive. These components will need to be replaced if found. It has always been a practice to use a pointed tool to poke up into the exhaust system where the deterioration spots are to see whether or not they crumble. Some models may have heat shield covering certain parts of the exhaust system , it will be necessary to remove these shields to have the exhaust visible for inspection also.
The three-way catalytic converter is an emission control device added to the exhaust system to reduce pollutants from the exhaust gas stream. It requires the use of unleaded fuel only. Periodic maintenance is not required but the condition of the entire system should be checked whenever the vehicle is raised for any kind of service.
The three-way catalytic converter is serviced by replacing the entire assembly. Always replace the exhaust manifold pipe, gasket and catalytic converter gaskets at the front and rear flanges when serving the catalytic converter.
Removal & Installation
Slip Joint Type
Before removing any component on the slip joint type exhaust system, ALWAYS squirt a liquid rust dissolving agent onto the fasteners for ease of removal. Start by unbolting the exhaust piece at both ends (if required). When unbolting the headpipe from the manifold, make sure that the bolts are free before trying to remove them. if you snap a stud in the exhaust manifold, the stud will have to be removed with a bolt extractor, which often means removal of the manifold itself. Next, remove the mounting U-bolts from around the exhaust pipe you are extracting from the vehicle. Don't be surprised if the U-bolts break while removing the nuts. Loosen the exhaust pipe from any mounting brackets retaining it to the floor pan and separate the components.
Slight twisting and turning may be required to remove the component completely from the vehicle. You may need to tap on the component with a rubber mallet to loosen it. In many cases, trying to save and/or salvage exhaust system parts may be more trouble than they are worth. Sawing tailpipes into pieces for easy removal and then installing new parts may make the most sense.
When installing exhaust components, loosely position all components before tightening any of the joints. Once you are satisfied with the fit, begin tightening the fasteners at the front and work your way back.