Chrysler 1991 Service Manual Supplement page 74

5.9L (DIESEL) ENGINES 9 - 11
SERVICE DIAGNOSIS - PERFORMANCE (CONT.)
CONDITION POSSIBLE CAUSES
CORRECTION
COOLANT TEMPERA-
TURE ABOVE NORMAL
(Cont'd)
Overfueled infection pump.
Plugged cooling passages in
radiator, head, head gasket or
block.
Engine overloaded.
Replace the injection pump.
Flush the system and fill with clean coolant.
Verify that the engine load rating is not being exceeded.
COOLANT TEMPERA-
TURE BELOW NORMAL
Too much air flow across the
radiator.
Incorrect thermostat, broken
thermostat jiggle pin or
contamination in thermostat.
Temperature sensor or gauge
inoperative.
Coolant not flowing by
temperature sensor.
Check/repair viscous fan as required.
Check and replace thermostat.
Verify that the gauge and sensor are accurate. If not, replace
gauge/sensor.
Check and clean coolant passages.
INSPECTION (ENGINE OIL LEAKS)
If an oil leak source is not readily identifiable, the
following steps should be followed:
(1) Attach an air hose with pressure gauge and
regulator to the dipstick tube.
(2) Disconnect the breather cap to air cleaner hose
at the breather cap end. Cap or plug breather cap
nipple.
(3) Remove the PCV valve from the cylinder head
cover. Cap or plug the PCV valve grommet.
(4) After the engine is sealed, set the air pressure
regulator NO HIGHER than 27 kPa (4 psi).
(5) Using a liquid soap solution or preferable a
stethoscope, inspect all suspected oil leak areas. If an
oil leak area is detected, repair per the service man-
ual instructions.
(6) If no leaks are detected, turn off the air supply
and remove the air hose and all plugs. Install the
PCV valve and breather cap hose. See step 7 and
check for higher pressure leaks occurring during nor-
mal engine operation.
(7) Clean the oil off the suspect oil leak area using
a suitable solvent. Drive the vehicle at various
speeds approximately 24 km (15 miles). Check the
engine for signs of an oil leak. If an oil leak is found,
repair per the service manual instructions.
J9109-254
(8) If the leakage occurs at the crankshaft rear oil
seal:
(a) Raise the vehicle.
(b) Remove torque converter or clutch housing
cover and inspect rear of block for evidence of oil.
A circular spray pattern generally indicates seal
leakage. Where leakage tends to run straight
down, possible causes are a porous block and the
rear cam and galley plugs. See Group 9, Engines
(Rear Main Bearing Oil Seals), for the proper seal
(and retainer) installation.
(c) If no leaks are detected while the crankcase is
pressurized 27 kPa (4 psi), very slowly turn the
crankshaft and watch for leakage. If a leak is de-
tected while turning the crankshaft, its possible
the crankshaft seal surface is damaged in the seal
area, minor nicks or scratches can be polished out
with emery cloth.
ENGINE OIL PRESSURE
(1) Remove oil pressure sending unit.
(2) Install Oil Pressure Line and Gauge Tool
C-3292.
(3) Start engine and record pressure (refer to Oil
Pressure in Engine Specifications for the proper pres-
sures).