Page 191
Radiator and Cooling System
Fig. 15. Main cooling fan thermoswitch in left-side of radiator (ar
261-9
Fig. 16. Fan and shroud assembly being removed.
row).
To remove radiator cooling fans
1. Disconnect the negative (-) battery cable. Disconnect
the fan harness connector and the ground strap.
2. Remove the screws securing the fan shroud to the radiator. Remove the fan and shroud as a unit. See Fig. 16.
3. Working at the bench, remove the screws or nuts holding the fan motor to the shroud assembly.
NOTE
• If the engine overtleats even though the fan cycles on and
off as specified, the fan may be running in reverse. Check that
the fan is drawing air through the radiator and not blowing air
out. Some fans were wired improperly at the connector. The
wires in the fan connector should mate with the same color
wires in the hamess connector.
• Always check the tightness of the fan to the shroud. These
fasteners can vibrate loose. Use a thread locking compound
on all screws or nuts.
Installation is reverse of removal. Use a thread locking compound such as Loctite® on the screws or nuts that secure the
fan motor to the shroud. Always test fan operation after reinstalling the fan/shroud assembly.
RADIATOR AND COOLING FANS
Page 192
Turbocharger
291-1
291 Turbocharger
General.
Turbocharger
Automatic Performance Control (APC)
Turbocharger and
APC Troubleshooting
Turbo Boost Pressure
To check and adjust boost pressure
291-1
APC Component Testing
291-1
291-1
To test APC solenoid valve
To test APC knock sensor
To test APC pressure sensor
To test APC bypass valve
Replacing Turbocharger ,
291-2
291-3
291-4
291-6
291-6
291-7
291-8
291-8
291-9
TABLES
a. Turbocharger and APC Troubleshooting ..... 291-3
GENERAL
This section covers turbocharger and Automatic Performance Control (APC) system service and repair. Special test
equipment is required for some of the test procedures. If this
equipment is not available, the tests should be left to an authorized Saab dealer.
Turbocharger
A schematic of the turbocharger with intercooler is shown in
Fig. 1. The exhaust-driven turbocharger rotates at very high
speeds and is precisely balanced. The turbocharger is cooled
and lubricated with engine oil. On 1988 and later models, the
turbocharger is also water-cooled. The turbocharger's boost
pressure is limited by a mechanical wastegate. When the boost
pressure exceeds a predetermined level, the wastegate opens
to bypass some of the exhaust gases around the turbine.
Automatic Performance Control (APC)
The Automatic Performance Control (APC) system enables
the engine to achieve optimum performance and good fuel
economy, regardless of the grade of fuel being used at any
given time. The APC system consists of simple electronic
components. See Fig. 2.
A knock sensor on the engine block senses the onset and
degree of engine knock and transmits an electronic signal to
the control unit. The control unit also receives intake manifold
pressure information from a pressure sensor and engine
speed information from the ignition system. Using this information, the APC control unit electrically modulates the APC
solenoid valve to regulate boost pressure via the wastegate.
Through the APC system, the boost pressure is allowed to
increase (up to a limit) until the engine begins to knock. It does
this by venting some of the manifold pressure away from the
wastegate and in effect '1ricking" the wastegate that the boost
pressure is lower than it really is. When the engine begins to
2. Turbocharger
4. Airflow
5. Intercooler outlet
3. Intercooler (intake air)
6. Intake manifold
1.
Exhaust manifold
Fig. 1. Turbocharger system.
knock, the solenoid valve closes and true boost pressure is
applied to the wastegate diaphragm and the wastegate valve
is pushed off its seat.
NOTE
In the event the APe system or the wastegate malfunction, allowing the boost pressure to exceed a safe level, the fuel
pump will be tumed off. On cars with LH 2.2, this feature is
handled by an overpressure switch. On 1989 and later cars
with LH 2.4, the LH control unit handles this feature. See 234
Fuel Pump and Fuel Tank for more infonnation on the overpressure switch.
GENERAL
Page 193
291-2
Turbocharger
-
Electrical wiring
c:::J Air hose
Electrical signal
from the engine
ignition system
(engine rpm)
89030-$21058
1. Knock sensor
2. Pressure sensor (transducer)
3. APC control unit
4. Solenoid valve
5. Ignition distributor
Fig. 2. Schematic of APC system,
TURBOCHARGER AND APe
TROUBLESHOOTING
Due to the extremely high speeds and temperatures, proper lubrication of the turbocharger is critical. Small oil passages
are drilled into the turbo housing and bearings. Piston-type
sealing rings are placed around the shaft at each end to prevent oil from entering the compressor and turbine housing.
There is a high rate of flow of oil to ensure the shaft floats on a
film of oil. See Fig. 3.
When the turbo bearings and seals become worn, the lubricating oil can slip past the seals and into the combustion
chamber. The result is blue-gray oil smoke exiting through the
tailpipe. When the bearings become severely worn, the turbocharger compressor and turbine impeller may contact the turbocharger housing, making loud screeching or thumping
noises.
The major cause of turbocharger bearing and seal failure is
due to carbon deposits caused by "coking" or baking of the oil
in the turbocharger's oil passages. During operation, the temperature of the turbocharger housing can exceed the boiling
point of the oil running through it. Because the oil is constantly
circulating, it stays cool enough to prevent coking. If the oil
pipes are clogged or if the engine is turned off before the turbocharger has had time to cool down, the oil can quickly coke.
When coking deposits form, the oil How to the turbocharger is
reduced. In addition, this substance is abrasive and can wear
the seals and bearings prematurely.
TURBOCHARGER AND APC TROUBLESHOOTING
Fig. 3. Cutaway view of turbocharger showing lubrication circuit.
If none of the above faults are present, but engine performance and the turbocharger's output is low, first check for any
loose or broken hoses. Check the small vacuum/pressure
hoses as well as the larger intake air hoses. Be sure to check
the hoses at the turbo bypass valve, which is directly below
the turbocharger. Check the electrical connectors to the APC
control unit (under rear seat on 1985 cars; at driver's side
wheel housing on all 1986 and later cars), the solenoid valve
(at radiator crossmember) and the pressure sensor (under
left-hand side of instrument panel). If there are any faults in
the APC system, the boost pressure will only boost to the "basic" pressure as described below.
In addition to the APC system components, there are two
other components that can reduce the turbocharger's boost
pressure. The cruise control vacuum switch and the brake
light switch (1986 and later cars) will revert the system to the
"basic" boost setting automatically whenever the brakes are
applied or the cruise control system is activated. If either one
of these components is faulty, the waste gate will open at a low
boost level. Testing and adjusting information for the brake
light switch is given in 364 Electric Controls and Switches.
Testing information for the cruise control vacuum switch is
given in 368 Cruise Control.
Besides low boost pressure, the boost pressure can also be
too high, and this can result in complete engine failure. Table
a lists turbocharger and APC system faults, their probable
causes, and corrective actions.
Page 194
Turbocharger
291-3
The first part of the pressure check measures basic boost.
The basic boost pressure is the base or "basic" setting of the
wastegate and is adjustable. This pressure setting is a safety
feature to prevent engine damage caused by detonation. In
the event of an APC component malfunction, the system reverts to the basic setting of the wastegate. The basic setting is
also selected whenever the cruise control system is selected
or the brake pedal is depressed (1986 and later models only).
NOTE
It is a good idea to measure the boost pressure as a first step
in turbocharger and APC troubleshooting.
Turbo Boost Pressure
There are two boost pressure measurements that should
be made to check the performance of the turbocharger and to
check that the APC system is operating.
The second part of the pressure check measures the efficiency of the turbocharger and also checks the operation of
the APC system. This setting is not adjustable and is regulated based on the quality of the fuel in the tank. The better the
quality of fuel in the tank, the higher the boost level.
Table a. Turbocharger and APe Troubleshooting
Symptom
Corrective action
Probable cause
-----------
1. Noise or vibration
a. Insufficient lubrication to turbo shaft
a. Remove and check the turbo oil supply pipe for clogging or
and bearing
from turbo unit
b. Leakage in the intake or exhaust
deposits. Check the oil pressure and oil flow to the turbocharger
b. Check for leaking seals (O-rings) or pipe connections. Tighten all
connections and replace defective seals
system
c. Turbo shaft unbalanced
c. Replace turbo unit
a. Leakage between compressor and
a. Check for leaking pipe connections. Tighten all connections
--
2. Boost pressure too
cylinder head or turbine and exhaust
system
low
b. Incorrectly adjusted charge pressure
c. Wastegate sticking open
b. Check and adjust basic boost and maximum boost
c. Clean and lubricate wastegate. Replace the wastegate assem
d. Partially clogged exhaust system
d. Check exhaust system for blockage, especially in the catalytic
e. Clogged air cleaner
e. Replace air cleaner
bly if it cannot be made to move freely
converter. Replace faulty exhaust components
f.
Binding turbo shaft
g. Faulty brake light switch (1986 and
f.
Replace turbo unit
g. Test switches and replace if faulty
later) or faulty cruise control vacuum
switch
h. Faulty APC component
h. Test the knock sensor, the pressure sensor, and the solenoid
valve. If no faults are found, the APC control unit may be faulty
a. Leak in hose at APC solenoid valve
a. Check for leaks and replace any faulty hoses. Test the APC sole
--
3. Boost pressure too
or faulty solenoid valve
high
b. Leaky wastegate diaphragm unit
c. Leaking hose to pressu re senso r 0 r
faulty pressure sensor
noid and replace if faulty
b. Replace diaphragm unit
c. Check for leaks and replace any faulty hoses. Test the pressure
sensor and replace if faulty
d. Wastegate sticking closed or binding
d. Clean and lubricate wastegate. Replace the wastegate assem
e. Incorrectly adjusted charge pressure
e. Check and adjust basic boost and maximum boost
f.
f. Test pressure sensor. If no faults are found the APC control unit
may be faulty
bly if it cannot be made to move freely
Faulty pressure sensor or APC
control unit
-
4. Normal boost
pressure despite
intensive knocking
a. APC system not working
b. Knock sensor or wiring to knock
a. Test APC system components
b. Test knock sensor and replace if faulty
deter faulty
c. Knock sensor not correctly tightened
c. Check that sensor is torqued to 14 Nm (10 ft-Ib)
to block
d. Wastegate sticking closed
d. Clean and lubricate wastegate. Replace the wastegate assembly if it can not be made to move freely
nJRBOCHARGER AND APC TROUBLESHOOTING
Page 195
---291-4
Turbocharger
CAUTION
Do not measure the maximum turbocharger boost pressure
by eliminating the knock sensor from the APC system. Although the system is designed to limit boost pressure based
on the input from the pressure sensor (and at even higher levels, the fuel pump is tumed off), the pressure at which this occurs may be too high if the fuel quality is low, resulting in
engine failure.
To check and adjust boost pressure
An accurate vacuum/pressure gauge with a long extension
hose is required to measure the boost pressure. See Fig. 4.
Hang the gauge from the rear view mirror for ease of viewing
to obtain the most accurate results. In addition, a helper is required to make the test described below.
l
I
Fig. 5. APe solenoid valve Wiring connectors being disconnected.
NOTE
When using Saab tool no. 8394074, the APC solenoid valve
can be isolated from the system by tuming the solenoid-valve
switch off. Make sure the knock detector switch is also off. See
Fig. 6.
.0.
'(JI
SAAB
IVrtlo
.0.
Ig,
o
APe
89032-S2027
ON [[0]0"
KNOCK-DETECTOR
Fig. 4. Vacuum/pressure gauge (Saab tool no. 8393 514) for measuring turbo boost pressure and for testing APC components.
ON [[0]0"
SOLENOID-VALVE
GD 9394074
0
89034-S2l1013
WARNING
The following test requires that the car be driven on the road
while checking the boost pressure on the gauge. This should
always be done using a helper. Do not make the test if a helper is not available to read and record the gauge results.
CAUTION
It is recommended that the highest octane-rated fuel available
be used when making this test. Otherwise the engine may
knock continually during the test, possibly causing engine
damage.
1. Run the engine until it is fully warmed up.
2. Working at the radiator crossmember, unplug the wiring
connectors from the solenoid valve. See Fig. 5.
TURBOCHARGER AND APC TROUBLESHOOTING
Fig. 6. Optional Saab APC test box (Saab tool no. 83 94 074).
Switches should be set to off position.
3. Using a pressure/vacuum gauge with a long hose, connect the gauge hose between the fitting on the intake
manifold and the hose leading to the pressure sensor.
See Fig. 7. Place the gauge in the passenger compartment, preferably hanging vertically from the rear view
mirror.
4. While driving the car on a long open stretch of road,
place the transmission in 3rd gear with the engine
speed at or below 1,500 rpm.
Page 196
Turbocharger
291-5
NOTE
Some late models may not have the wastegate seal installed,
as the seal has been discontinued in production and does not
need to be reinstalled.
Rg.7. Pressure/vacuum gauge hose being connected to fitting
on intake manifold. Use a long hose so gauge can reach
into passenger compartment.
NOTE
On cars with automatic transmission, place the transmission
in the "1" drive position.
5. Depress the accelerator pedal to the floor until the engine speed approaches 3,000 rpm. Apply the brakes
hard as necessary to keep rpm at 3,000 while continuing to hold the accelerator pedal to the floor. Within a
short time, the gauge reading will stabilize. Have the
helper record the gauge reading at this point.
CAUTION
Make the test as quickly as possible (within three to five seconds) to avoid overheating the brakes. If the test is to be made
a second time, drive the car about one mile before repeating
the test to allow the brakes to cool.
. Fig. 8. Wastegate actuator (diaphragm) rod.
7. While holding the rod stationary, loosen the locknut and
thread the end piece in or out to readjust the length of
the rod. See Fig. 9. Then tighten the locknut. Reinstall
the rod to the lever. Recheck the basic boost pressure
as described above. If necessary, readjust the length of
the rod.
CAUTION
Do not allow the wastegate actuator rod to tum the diaphragm
or the diaphragm may be damaged.
Turbocharger Basic Boost Pressure
• All ex. 1987 and later
SPG models. . . . . . . .. 0.35±0.03 bar (5.0±0.4 psi)
• 1987 and later
SPG models. . . . . . . .. 0.40±0.03 bar (5.8±0.4 psi)
6. If the basic boost setting is incorrect, allow the turbocharger to cool. Then remove the anti-tamper seal (if
installed) and the circlip from the end of the wastegate
actuator rod. Remove the rod from the wastegate lever.
See Fig. 8.
Fig. 9. Hold wastegate actuator rod stationary with pliers when adjusting the end piece or tightening the locknut.
CAUTION
Use extreme care when working near a hot turbocharger.
nJRBOCHARGER AND APC TROUBLESHOOTING
Page 197
291-6
Turbocharger
NOTE
If the charging pressure is too low, tum the end piece clockwise to shorten the rod. If the pressure is too high, turn the end
piece counter clockwise to lengthen the rod. Adjust the rod in
small increments. One complete tum of the end piece roughly
equates to a 0.04 bar (0.6 psi) pressure change.
CAUTION
Do not attempt to adjust the maximum boost pressure through
the waste gate actuator rod. This will not increase the boost
pressure or engine performance, as maximum boost pressure
is controlled by the APC system.
12. When the pressure test is complete, remove the pres
8. When the basic boost pressure setting is correct, reconnect the wiring connectors to the solenoid valve.
Keep the vacuum! pressure gauge connected.
9. On 1986 and later cars, disconnect the white wire from
the brake light switch above the brake pedal.
NOTE
On 1986 and later cars, a voltage signal via the brake light
switch (white wire) is applied to the APC control unit when the
brakes are applied. This reduces the maximum boost pressure to the basic boost setting of the wastegate.
10. Again, drive the car on a long open stretch of road and
repeat the above test. In a short time, the gauge reading should stabilize. Have the helper record the reading
at this point.
sure gauge and reconnect the wiring at the brake light
switch, if applicable.
APC COMPONENT TESTING
To test APe solenoid valve
The APC solenoid valve is mounted in the engine compartment, at the radiator crossmember. Based on the signal from
the APC control unit, the valve regulates the control pressure
to the wastegate. See Fig. 10. When the solenoid is closed
(connection between port C and W only), the wastegate will
open at a low (basic) boost pressure. When the solenoid is
open (all three ports open), there is not enough pressure to
open the wastegate and the boost pressure is allowed to increase until engine knock is detected.
CAUTION
Make the test as quickly as possible. (in three to five seconds)
to avoid overheating the brakes. If the test needs to be m~de
a second time, drive the car about one mile before repeating
the test to allow the brakes to cool.
NOTE
The specifications listed below should be used only as a guide.
Do not expect the gauge reading to reach this level, as this
maximum pressure is controlled by the signal from the knock
sensor. When engine knocks, the wastegate will open, resulting
in gauge reading considerably lower than that specified.
Turbocharger Maximum Boost Pressure
• All ex. 1987 and later
SPG models
• 1987 and later
SPG models
L
89038
O.75±O.05 bar (1 O.9±O.7 psi)
O.85±O.05 bar (12.3±O.7 psi)
11. If the pressure stabilizes at the basic setting or goes
above the maximum setting, test the turbocharger APC
components as described below. If the pressure reading is only slightly above the basic setting even though
the gas is of high-quality, the turbocharger may be
faulty. See the troubleshooting table given earlier.
APCCOMPONENTTESTING
_
Fig. 10. APC solenoid valve. Port C is the pressure line from the turbo
compressor (true manifold pressure), W is the pressure line
to the wastegate, and R is a bleed or return line back to the
turbo compressor.
1. Disconnect the electrical connectors from the APC solenoid valve. See Fig. 5 given above.
2. Disconnect the hose between the turbo compressor inlet and the connection marked "R" on the solenoid.
Page 198
Turbocharger
3. Using jumper wires, connect battery voltage to the solenoid terminals. Blow through the disconnected hose
(port R) and check that air passes freely through the
valve. See Fig. 11.
291-7
1. Disconnect the harness connector from the APC control unit. Using a digital voltmeter (set to VAC scale),
connect it to control unit terminals 2 and 3 on 1985
models or 16 and 17 on all 1986 and later models. See
Fig. 13.
NOTE
On 1985 models, the APC control unit is under the rear seat.
On 1986 and later models, the control is mounted to the lefthand side wheel well in the engine compartment.
Fig. 11. APC solenoid being tested. When battery voltage is ap
plied to terminals, air should pass through valve.
4. Remove the voltage and check air does not pass
through the valve. If any faults are found, the valve is
faulty and should be replaced.
89041
Fig. 13. Voltmeter connected to knock sensor terminals in APC con
trol unit connector. Back-probe connector to prevent damaging connector terminals.
To test APe knock sensor
The knock sensor is mounted to the engine block between
cylinders no. 2 and 3, below the intake manifold. See Fig. 12.
The sensor functions like a microphone and is able to convert
mechanical vibration (knock) into a small AC voltage signal.
The APC control unit is programmed to react to the signals
whose frequencies are characteristic of combustion chamber
noise.
2. Gently tap on the knock sensor mounting bolt. The voltmeter should register a small voltage and the reading
should vary depending on the intensity of the tap.
3. If the knock sensor does not respond to the tapping, remove the sensor from the engine. Then connect the
voltmeter directly to the sensor terminals and repeat
the above tapping test. If the sensor now tests good,
check the wiring from the sensor connector to the control unit.
If the sensor does not respond as specified, it is faulty and
should be replaced. When replacing the sensor, thoroughly
clean the mounting surface on the engine and the threads on
the mounting bolt. Install the new sensor with the electrical
connector towards the front, offset to the left about 20°. See
Fig. 14. Torque the bolt to the specification given below while
holding the sensor steady.
Tightening torque
• APC knock sensor
to engine block
14 Nm (10 ft-Ib)
Fig. 12. APC knock sensor (arrow), Sensor is bolted to engine
block beneath intake manifold.
APC COMPONENT TESTING
Page 199
291-8
Turbocharger
Fig. 14. Knock sensor installation angle. Hold sensor steady when
tightening bolt.
Fig. 15. Pressure sensor mounting bracket beneath left hand side of dashboard. Pressure sensor shown at arrow.
To test APC pressure sensor
The sensor monitors the turbo boost pressure in the manifold downstream of the throttle. The pressure is converted into
an electrical resistance signal and is monitored by the control
unit.
The pressure sensor is mounted beneath the left-hand
(driver's) side of the dashboard. A hand-pump and pressure
gauge is required to accurately check the sensor.
1. Disconnect the harness connector from the APC control unit. Using a digital voltmeter (set to resistance
scale), connect it to control unit terminals 8 and 9 on
1985 models or 10 and 23 on all 1986 and later models.
Check the sensor's resistance. If any faults are found,
the sensor should be replaced.
4. Disconnect the hose leading to the sensor and connect
a pressure gauge and hand-pump. See Fig. 16. Pump
the pressure up to 1 bar (14.5 psi), then reduce the
pressure to 0.6 bar (8.7 psi) while tapping lightly on the
side of the sensor. Check the sensor's resistance. If
any faults are found, the sensor should be replaced.
Pressure Sensor Test Specifications
• resistance at 0.6 bar (8.7 psi)
pressure . . . . . . . . . . . . . . . . . . . . .. 83 to 92 ohms
Pressure Sensor Test Specifications
• resistance at atmospheric
pressure
5 to 13 ohms
NOTE
On 1985 models, the APC control unit is under the rear seat.
On 1986 and later models, the control is mounted to the lefthand side wheel well in the engine compartment.
Fig. 16. Pressure gauge and pressure pump connected to pressure
sensor (shown schematically).
2. Remove the center storage console and the lower
dashboard pad as described in 853 Dashboard and
Consoles.
To test APC bypass valve
3. Unscrew the pressure sensor mounting bracket from
the relay panel member to access the sensor. See Fig. 15.
The vacuum controlled bypass valve redirects turbocharger
output (boost) to the suction side of the compressor when the
APCCOMPONENTTESTING
Page 200
Turbocharger
throttle is snapped shut. This dampens the distribution of intake air flow that results when full boost is suddenly bounced
off the closed throttle plate. See Fig. 17.
291-9
NOTE
Inspect the hose clamps on the bypass valve. If the old style
plastic clamps are installed, they should be replaced with metal screw-type clamps. The plastic clamps are known to break
easily, allowing the pressure from the turbocharger to blow the
hoses off the valve.
89045
"-------------------------~~
Fig. 17. Schematic of APC system showing the operation of the bypass valve (A).
The symptoms of a faulty bypass valve are usually minor
driveability problems (slight surging when opening the throttle
on cars with manual transmission), and noises (hooting
sounds). The bypass valve is mounted below the center of the
turbocharger. Use a hand-held vacuum pump to accurately
test the valve.
NOTE
Some early 1985 models with automatic transmission may not
have a bypass valve.
Fig. 18. APC bypass valve shown with vacuum applied to diaphragm.
The valve diaphragm should hold valve stay off its seat.
Replacing Turbocharger
Turbocharger removal and installation is done by first removing the exhaust manifold with the turbocharger as a complete unit. with the manifold removed, unbolt the turbocharger
from the manifold. See 252 Exhaust System for removal and
installation of the exhaust manifold.
NOTE
1. With the engine cold, remove the bypass valve below
the turbocharger.
WARNING
Do not remove the bypass valve when the engine is hot. The
turbocharger operates at very high temperatures.
2. Using a hand-pump, apply vacuum to the fitting on the
valve and check that it lifts off its seat. See Fig. 18. With
the vacuum applied, check that the valve stays open. If
the valve slowly closes, the diaphragm is leaking and
the valve should be replaced.
The turbocharger-to-exhaust manifold mounting nuts are selflocking and should always be replaced.
When replacing the turbocharger, the oil return and supply
pipes should be removed and thoroughly cleaned using a stiff
brush and solvent. See Fig. 19. If the pipes cannot be completely cleaned, they should be replaced. The engine oil and
oil filter should also be changed.
NOTE
If the turbocharger is being replaced because of excessive exhaust smoke, there will be some oil remaining in the exhaust
system that will most likely cause smoking upon start-up. Be
sure to test drive the car long enol.1gh to clear the leftover oil
from the exhaust system before suspecting that the replacement turbocharger is faulty.
APC COMPONENT TESTING