Chrysler RAM TRUCK 2500 1994 Service Manual page 890

* EXHAUST SYSTEM AND INTAKE MANIFOLD 11 - 1
EXHAUST SYSTEM AND INTAKE MANIFOLD
C O N T E N T S
page
EXHAUST SYSTEM DIAGNOSIS 3
GENERAL INFORMATION 1
SERVICE PROCEDURES (DIESEL ENGINES) .. 13
page
SERVICE PROCEDURES (GASOLINE ENGINES) . 4
SPECIFICATIONS 24
G E N E R A L INFORMATION
EXHAUST SYSTEM
The gasoline engine exhaust system consists of en­
gine exhaust manifolds, exhaust pipes, catalytic con­
verters), extension pipe (if needed), exhaust heat
shields, muffler and exhaust tailpipe (Fig. 1).
The diesel engine exhaust system consists of an en­
gine exhaust manifold, turbocharger, exhaust pipe,
catalytic converter, extension pipe (if needed), muffler
and exhaust tailpipe (Fig. 2).
The engine exhaust manifolds on gasoline engines
are equipped with ball flange outlets to assure a
tight seal and strain free connections.
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 from the engine or body.
When inspecting an exhaust system, critically in­
spect 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 re­
pair.
When replacement is required, use original equip­
ment parts (or their equivalent). This will assure
proper alignment and provide acceptable exhaust
noise levels.
CAUTION: Avoid application of rust prevention com­
pounds or undercoating materials to exhaust s y s ­
tem floor pan exhaust heat shields. Light overspray
near the edges is permitted. Application of coating
will result in excessive floor pan temperatures and
objectionable fumes.
CATALYTIC CONVERTER
The stainless steel catalytic converter body is de­
signed 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 un-
burned 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 in gas engines to
avoid contaminating the catalyst core.
EXHAUST HEAT SHIELDS
Exhaust heat shields are needed to protect both the
vehicle and the environment from the high tempera­
tures developed by the catalytic converter. The com­
bustion reaction facilitated by the catalyst releases
additional heat in the exhaust system. Under severe
operating conditions, the temperature increases in
the area of the reactor. Such conditions can exist
when the engine misfires or otherwise does not oper­
ate at peak efficiency. 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 GAS RECIRCULATION (EGR)—
(GASOLINE ENGINES)
Tb assist in the control of oxides of nitrogen (NOx)
in engine exhaust, all engines are equipped with an
exhaust gas recirculation system. The use of exhaust
gas to dilute incoming air/fuel mixtures lowers peak
flame temperatures during combustion, thus limiting
the formation of NOx.
Exhaust gases are taken from openings in the ex­
haust gas crossover passage in the intake manifold.
Refer to Group 25, Emission Control Systems for
complete description, diagnosis and service proce­
dures of the exhaust gas recirculation system and
components.