Exhaust System - Jeep Wrangler 1999 Electronic Service Manual

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GENERAL INFORMATION
CATALYTIC CONVERTER . . . . . . . . . . . . . . . . . . . 1
EXHAUST HEAT SHIELDS . . . . . . . . . . . . . . . . . 1

EXHAUST SYSTEM . . . . . . . . . . . . . . . . . . . . . . . 1

DIAGNOSIS AND TESTING
EXHAUST SYSTEM . . . . . . . . . . . . . . . . . . . . . . . 3
GENERAL INFORMATION
EXHAUST SYSTEM
WARNING: THE NORMAL OPERATING TEMPERA-
TURE OF THE EXHAUST SYSTEM IS VERY HIGH.
THEREFORE, NEVER ATTEMPT TO SERVICE ANY
PART OF THE EXHAUST SYSTEM UNTIL IT IS
COOLED. SPECIAL CARE SHOULD BE TAKEN
WHEN WORKING NEAR THE CATALYTIC CON-
VERTER. THE TEMPERATURE OF THE CONVERTER
RISES TO A HIGH LEVEL AFTER A SHORT PERIOD
OF ENGINE OPERATION TIME.
The basic exhaust system consists of an engine
exhaust manifold, exhaust pipe with oxygen sensor,
catalytic converter with oxygen sensor, exhaust heat
shield(s), muffler and exhaust tailpipe (Fig. 1) (Fig.
2).
The exhaust system uses a single muffler with a
catalytic converter consisting of dual ceramic mono-
liths.
The 4.0L engines use a seal between the engine
exhaust manifold and exhaust pipe to assure a tight
seal and strain free connections (Fig. 2).
The exhaust system must be properly aligned to
prevent stress, leakage and body contact. If the sys-
tem contacts any body panel, it may amplify objec-
tionable noises originating from the engine or body.
When inspecting an exhaust system, critically
inspect for cracked or loose joints, stripped screw or
bolt threads, corrosion damage and worn, cracked or
broken hangers. Replace all components that are
badly corroded or damaged. DO NOT attempt to
repair.
When replacement is required, use original equip-
ment parts (or their equivalent). This will assure
proper alignment and provide acceptable exhaust
noise levels.
EXHAUST SYSTEM
CONTENTS
page
REMOVAL AND INSTALLATION
CATALYTIC CONVERTER/EXHAUST PIPE . . . . . . 3
MUFFLER AND TAILPIPE ASSEMBLY . . . . . . . . 4
SPECIFICATIONS
TORQUE SPECIFICATIONS . . . . . . . . . . . . . . . . . 5
CAUTION: Avoid application of rust prevention
compounds or undercoating materials to exhaust
system floor pan exhaust heat shields. Light over
spray near the edges is permitted. Application of
coating will result in excessive floor pan tempera-
tures and objectionable fumes.
CATALYTIC CONVERTER
The stainless steel catalytic converter body is
designed to last the life of the vehicle. Excessive heat
can result in bulging or other distortion, but exces-
sive heat will not be the fault of the converter. If
unburned fuel enters the converter, overheating may
occur. If a converter is heat-damaged, correct the
cause of the damage at the same time the converter
is replaced. Also, inspect all other components of the
exhaust system for heat damage.
Unleaded gasoline must be used to avoid contami-
nating the catalyst core.
EXHAUST HEAT SHIELDS
Exhaust heat shields are needed to protect both
the vehicle and the environment from the high tem-
peratures developed by the catalytic converter. The
catalytic converter releases additional heat into the
exhaust system. Under severe operating conditions,
the temperature increases in the area of the con-
verter. Such conditions can exist when the engine
misfires or otherwise does not operate at peak effi-
ciency.
DO NOT remove spark plug wires from plugs or by
any other means short out cylinders. Failure of the
catalytic converter can occur due to a temperature
increase caused by unburned fuel passing through
the converter.
DO NOT allow the engine to operate at fast idle for
extended periods (over 5 minutes). This condition
may result in excessive temperatures in the exhaust
system and on the floor pan.
EXHAUST SYSTEM 11 - 1
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