Auto Engine Performance and Driveability, 4th Edition Page 396 (396 of 528)

396 Auto Engine Performance and Driveability
Copyright by Goodheart-Willcox Co., Inc.
valve using two wrenches to avoid damaging the tub-
ing, Figure 18-36A. Compare the old and replacement
valves, Figure 18-36B. Then, install the new valve on the
pipe, Figure 18-36C. Reattach the hose and recheck sys-
tem operation.
Air Pump Replacement
The air injection pump is replaced when it is defec-
tive, rather than repaired. Begin removal of the pump by
loosening the attaching bolts enough to slide the pump
and loosen the drive belt. Then, remove the drive belt and
hoses. Finish removing the attaching bolts and lift the pump
from the engine.
Before installing the new pump, check the hoses for
cracks. Replace any hoses that are cracked. Install the new
pump by reversing the removal process. Tighten the belt to
specifi cations. Recheck pump operation.
Note: Some pulleys are either pressed on
or bolted to the pump and do not come
with the replacement pump. If the pulley
is to be used with the new pump, remove the pulley
before removing the old pump from the engine.
Diverter and Switching Valve Replacement
Diverter and switching valves may be mounted on the
top or side of the air pump, Figure 18-37. Some diverter
valves are separate from the air pump and are replaced by
disconnecting them from the attaching hoses. Remove the
electrical connections and hoses, then remove the screws
holding the valve to the air pump. Next, remove the valve
from the air pump.
Use new gaskets when reinstalling the valve. Reinstall
the diverter valve and tighten the attaching screws. Reattach
the hoses and electrical connectors. After reinstalling any
diverter or switching valve assembly, recheck the operation
of the air pump system.
Figure 18-36. Replacing a check valve in an air injection sys-
tem. A—Use two wrenches to avoid damaging the tubing.
B—The new valve may look slightly different, but should have the
same function. C—Install the new valve on the pipe. Remember
to use two wrenches to tighten the valve.
Figure 18-37. Diverter valves are located on or near the pump.
Electrical connectors allow the ECM to control the valve.
Valve assembly
A
B
C

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396 Auto Engine Performance and Driveability
Copyright by Goodheart-Willcox Co., Inc.
valve using two wrenches to avoid damaging the tub-
ing, Figure 18-36A. Compare the old and replacement
valves, Figure 18-36B. Then, install the new valve on the
pipe, Figure 18-36C. Reattach the hose and recheck sys-
tem operation.
Air Pump Replacement
The air injection pump is replaced when it is defec-
tive, rather than repaired. Begin removal of the pump by
loosening the attaching bolts enough to slide the pump
and loosen the drive belt. Then, remove the drive belt and
hoses. Finish removing the attaching bolts and lift the pump
from the engine.
Before installing the new pump, check the hoses for
cracks. Replace any hoses that are cracked. Install the new
pump by reversing the removal process. Tighten the belt to
specifi cations. Recheck pump operation.
Note: Some pulleys are either pressed on
or bolted to the pump and do not come
with the replacement pump. If the pulley
is to be used with the new pump, remove the pulley
before removing the old pump from the engine.
Diverter and Switching Valve Replacement
Diverter and switching valves may be mounted on the
top or side of the air pump, Figure 18-37. Some diverter
valves are separate from the air pump and are replaced by
disconnecting them from the attaching hoses. Remove the
electrical connections and hoses, then remove the screws
holding the valve to the air pump. Next, remove the valve
from the air pump.
Use new gaskets when reinstalling the valve. Reinstall
the diverter valve and tighten the attaching screws. Reattach
the hoses and electrical connectors. After reinstalling any
diverter or switching valve assembly, recheck the operation
of the air pump system.
Figure 18-36. Replacing a check valve in an air injection sys-
tem. A—Use two wrenches to avoid damaging the tubing.
B—The new valve may look slightly different, but should have the
same function. C—Install the new valve on the pipe. Remember
to use two wrenches to tighten the valve.
Figure 18-37. Diverter valves are located on or near the pump.
Electrical connectors allow the ECM to control the valve.
Valve assembly
A
B
C

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Chapter 18 Diagnosis and Repair of the Emission Control and Exhaust Systems 395
Copyright by Goodheart-Willcox Co., Inc.
of the manifold studs. If the diaphragm can be serviced,
separate it from the valve assembly. If only the diaphragm
is being replaced, make sure that the valve moves freely.
Loosen it with penetrating oil and light hammer tapping if
needed. Reassemble the valve and diaphragm as necessary
and reinstall the assembly on the engine. Be sure to check
operation after the new parts are installed.
Thermal Vacuum Valve
To replace the thermal vacuum valve, depressurize
and drain the cooling system to a level below the switch.
Use a box-end wrench or socket to remove the switch.
Specialized sockets are available to remove these switches.
Compare the old and new switches. Coat the threads of
the new switch with the correct type of sealant and install
the switch in the coolant passage. Recheck operation after
installing the switch.
EGR Valve
The EGR valve is usually mounted on the top or side
of the engine. Refer to Figure 18-34. Start by removing
the electrical and vacuum connections. Then, remove the
bolts holding the valve to the intake manifold. If the EGR
bolts are diffi cult to turn, spray the bolts with penetrating
oil before continuing removal. Finally, pull the valve from
the engine.
Check the assembly for carbon deposits that may be
holding the valve open. Some EGR valves can be cleaned
and reused by striking the pintle with a soft-faced hammer
to knock loose any accumulated deposits, Figure 18-35.
Be careful not to damage the valve during this operation.
Also check the ports in the intake and exhaust manifolds for
excessive carbon buildup and clean if necessary.
If the valve has a non-integral position sensor, remove
the attaching screws and separate the sensor from the valve
body. Assemble the sensor on the new valve body using a
new gasket.
Before reinstalling the valve, check the EGR passages
for carbon buildup and clean them as necessary. Place a
new gasket over the EGR opening, then reinstall the EGR
valve and attaching screws. Reattach the vacuum hose
and electrical connector. After reinstalling the EGR valve,
recheck the operation of the system.
EGR solenoids cannot be repaired. They are replaced
as a unit. To replace the solenoid, disconnect the electrical
connectors and vacuum lines. Then, remove the fasteners
holding the solenoid to the bracket. Compare the new and
old solenoid assemblies to ensure that they are correct.
Then, install the new solenoid. Recheck EGR operation
after the solenoid is installed.
Note: On a few systems, the EGR solenoid
is part of the EGR valve and diaphragm
assembly. If the solenoid is defective, the
entire valve assembly must be replaced.
Air Injection System
The air injection system is comprised of the air-injec-
tion pump, drive belt, diverter valve(s), check valves, and
associated hoses and piping. Most of these parts are easily
removed. The valves and hoses can be removed by loosen-
ing the hoses and any attaching hardware. The fi ttings for
the exhaust system check valve and manifold tubing often
corrode at the exhaust manifold. If they are hard to remove,
soak them with penetrating oil and use a fl are-nut or box-
end wrench to loosen the threads. Always use new gaskets
where applicable for reinstallation.
Check valves commonly fail before other parts of
the air injection system. Begin removal of the check
valve by detaching the hose. Then, remove the old check
Figure 18-34. EGR valves are normally bolted directly to the
intake manifold or plenum. Some are remotely mounted close to
the engine and use a bolt-on pipe or passage.
Figure 18-35. If an EGR valve must be reused, it can be cleaned.
If the pintle is sticking, clean the valve and tap lightly on the base
with a soft-faced hammer. (Subaru)
Soft-faced hammer

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Chapter 18 Diagnosis and Repair of the Emission Control and Exhaust Systems 397
Copyright by Goodheart-Willcox Co., Inc.
Exhaust System Components
Components in the exhaust system are relatively easy
to replace. The vehicle should be on a lift to gain enough
clearance to maneuver the pipes. Replacement of exhaust
manifolds and gaskets are discussed in Chapter 19.
Warning: Always wear eye protection when
working on an exhaust system. The system
contains large amounts of loose rust that
will dislodge when the system is disturbed.
The exhaust system is attached to the underbody of the
vehicle by fl exible hangers. The hangers allow the exhaust
piping to move with the engine. Most exhaust pipes slip
together and are sealed by special clamps called saddle
clamps, or simply muffl er clamps.
Some pipes have fl anges that match a fl ange on the
mating pipe. Flanges are tightly held together by fl ange col-
lars and bolts. Some fl anges use a gasket between the mating
surfaces. See Figure 18-38. Other fl anges are bell-mouthed
and do not use a gasket. Bell-mouthed fl anges usually use
separate collars on each pipe to allow the fl anges to mate
closely with each other at any angle. Flanges are often used
to connect the exhaust pipes to the exhaust manifold.
To begin replacing exhaust system components,
remove the exhaust hangers that hold the sections to be
replaced. Then, loosen and remove the pipe fasteners.
If the fasteners are badly corroded, cut them off using a
power cutting wheel, chisel, or torch. Since exhaust clamps
are subjected to extreme heat and corrosive elements, it
is recommended that the new clamps be used instead of
reinstalling the old clamps.
Note: Use generous amounts of penetrating
oil on all exhaust system fasteners. The
fasteners will likely be hard to remove.
Removing Fitted Exhaust Components
When removing pipes that slip together, carefully cut
or chisel the defective pipe or component from the pipe
that is to be reused. Heat from a torch can also be used, if
carefully applied. If the pipe to be replaced is the outside
pipe, split the pipe down the entire length of the joint using
a chisel. Then, twist the outer pipe and pull it from the inner
pipe. If the pipe to be replaced is the inside pipe or the joint
is welded, use an exhaust pipe cutter to cut the pipe off
just before the joint with the outside pipe. Then, split and
collapse the inner pipe inward using a curved chisel. When
the inner pipe is collapsed enough, twist and pull it from
the outer pipe with a pair of adjustable pliers.
Warning: If a torch is used to heat or cut off
an exhaust system part, be careful not to
apply heat to the underside of the vehicle.
The heat from the torch could start a fi re inside of
the vehicle. Do not use a torch near the fuel tank,
fuel fi lter, or fuel lines. Once a part has been heated,
use heavy gloves or pliers to touch or grab the part.
When installing slip-fi t pipes and components, it may
be necessary to expand the old pipe. This can be done by
using an exhaust-pipe-expansion tool. Slip the new part onto
or into the exhaust system and install new clamps. Tighten
the clamp at about the midpoint on the sleeve where the
two parts meet. Once installed, reinstall the exhaust system
on the vehicle along with any heat shields and other parts
that were removed. Finally, road test the vehicle, making
sure that no part of the exhaust system rattles against the
body or heat shield.
Note: While it is not necessary in most
cases, some technicians will place one or
more spot welds on the edge of an exhaust
slip joint. This ensures that the two parts will not
slip and come apart with movement of the exhaust
system.
Figure 18-38. Flanged connections allow for movement between
fi xed and moving parts. The connection between the exhaust
manifold and exhaust pipe is almost always a fl anged connec-
tion. (Toyota)
Exhaust gas flow
Exhaust pipe
Ball-shaped
joint
Spring
Flange
Gasket
Bolt
Exhaust manifold

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