398 Auto Engine Performance and Driveability
Copyright by Goodheart-Willcox Co., Inc.
Removing Flanged Exhaust Connectors
If the mating pipes are fl anged, remove the bolts from
the collars. Then, remove the collars (if separate) and lower
the pipe from the vehicle. Once the old exhaust system
components have been removed, carefully clean the mat-
ing surfaces on the parts to be reused. If a fl anged pipe
uses a gasket, make sure all of the old gasket material is
removed from all pipes that will be reused. The new parts
can be installed by fi rst slipping them into position. Lightly
attach the pipe clamps or fl ange bolts.
Before tightening any of the exhaust components,
check the entire exhaust system for correct placement and
alignment. Ensure that no part of the exhaust system con-
tacts any heat shields or the underside of the vehicle. Once
alignment is correct, tighten all of the clamps and hangers.
Then, reinstall the pipe hangers that have been removed.
Finally, road test the vehicle, making sure that no part of the
exhaust system rattles against the body or heat shield.
Catalytic Converters
Replacing catalytic converters is similar to replac-
ing muffl ers and resonators. However, some extra safety
precautions are necessary when removing converters.
A properly operating converter becomes very hot during
operation. The temperature of the converter can reach as
much as 1200°F (650°C). Due to the mass of the catalyst
elements, the converter cools much more slowly than other
exhaust system parts. Therefore, extra care should be taken
to avoid burns when working on or around the converter.
Some converters are fi lled with coated pellets, which
can be changed without removing the converter. The pel-
let-changing procedure requires a special tool. However,
most converters, even pellet types, are simply replaced.
Since the mass of the converter makes it much heavier
than other exhaust system parts, make sure the converter is
adequately supported before removing the hanger fasten-
ers. Most converters have a heat shield that protects the
area of the vehicle above the converter from excessive
heat. Most heat shields are welded to the converter and
replaced when the converter is replaced. However, a few
heat shields are bolted around the converter. These shields
should be removed before removing the converter.
Converter Removal
The converter can be removed by removing clamps
attaching the pipe and hanger and then lowering the con-
verter from the vehicle. The converter sometimes has fl anged
connectors and does not have to be chiseled or heated to
be removed from the exhaust system, Figure 18-39.
Most exhaust system hangers are placed on pipes sup-
porting the converter to isolate them from the converter’s
heat. Most converters are dual-bed types with a separate
inlet connection for the air pump pipe. Remove this pipe by
loosening the clamp, heating the slip joint with a torch, and
sliding the pipe from the converter. Do not damage these
pipes or they will need to be replaced.
Some V-type engines have two converters, one installed
in each side of the Y-pipe from the exhaust manifolds. These
converters are usually welded in place and are changed by
replacing the entire Y-pipe assembly. See Figure 18-40. The
Y-pipe sometimes contains the oxygen sensors. The sensor
electrical connectors should be detached before the pipe
is removed.
Note: The converter contains precious
metals, such as platinum. These elements
are extremely expensive and becoming
increasingly hard to fi nd. Used converters are
recycled to recover the platinum and other precious
metals contained in the catalyst. Do not simply
dispose of the old converter as scrap. Find out
where it should be turned in for a core credit.
Figure 18-39. Gaskets are normally used on fl anged connec-
tions to the catalytic converter. Some fl anged connections use a
doughnut-type gasket.
Flanged
connection
Gasket
Figure 18-40. Y-pipe assemblies used with V-type engines
often have two or more converters. The Y-pipe is often replaced
with the converters.
Y-pipe
Converter