WATER PUMP DIAGNOSIS
A quick test to tell whether or not the pump is work-
ing is to see if the heater warms properly. A defective
pump will not be able to circulate heated coolant
through the long heater hoses. For additional diagnosis,
refer to Cooling System Diagnosis in this section. For
water pump inspection, refer to Cleaning and Inspec-
tion, Water Pump for procedures in this section. The
water pump on all models can be replaced with-
out discharging the air conditioning system.
NOTE: It is normal for the water pump to weep a
small amount of coolant from the weep hole (black
stain on water pump body—3.2/3.5L, or at weep
passage below the thermostat housing—2.7L). Do
not replace the water pump if this condition exists.
Replace the water pump only if a heavy deposit or a
steady flow of engine coolant is evident on water
pump body (3.2/3.5L), or from the weep passage
(2.7L). This condition indicates a shaft seal failure.
Be sure to perform a thorough analysis before
replacing the water pump.
RADIATOR FAN CONTROL
Cooling fan control can be accomplished five ways.
A pressure transducer on the air conditioning com-
pressor discharge line sends a signal to the Power-
train Control Module (PCM) which will activate both
fans if necessary. In addition to this control, the fans
are turned on based on coolant temperature sensor,
intake air temperature sensor, output speed sensor,
and transmission oil temperature sensor output to
the PCM. The PCM switches the fans on through the
fan relays. Refer to Wiring Diagrams Manual for cir-
cuit and diagnostics.
The PCM provides fan control for the following
conditions:
• Regardless of coolant temperature the fan will
not run during cranking until the engine starts.
• Fans will run in accordance with the specifica-
tions listed in the following operation charts.
RADIATOR FAN OPERATION—2.7L ENGINE
ENGINE COOLANT TEMPERATURE
INTAKE (CHARGE)
TEMPERATURE
A/C Off A/C On
Engine @ Idle<2 Km/h (1
MPH) Vehicle Speed
Fan
Speed
Low High Low High Low High Low High
Fan
On:
106°C
(223°F)
110°C
(230°F)
105°C
(221°F)
110°C
(230°F)
99°C (210°F)
- After 2nd
Fan Cycle
110°C (230°F) 63°C (145°F)
if
coolant<93°C
(199°F)
67°C (153°F)
60°C (140°F)
if coolant
>99°C
(210°F)
Fan
Off:
102°C
(216°F)
107°C
(225°F)
102°C
(216°F)
106°C
(223°F)
Fan on time =
4 minutes*
105°C (221°F) Fan on time =
8 minutes*
Fan on time =
4 minutes*
*Minimum fan on time = 90 seconds
A/C PRESSURE
TRANSMISSION OIL TEMPERATURE
Fan Speed Low High Low High
Fan On:
1,448 Kpa (210
psi)
1,717 Kpa (249 psi) 109°C (228°F) 111°C (232°F)
Fan Off:
1,207 Kpa (175
psi)
1,503 Kpa (218 psi) 104°C (220°F) 109°C (228°F)
LH COOLING SYSTEM 7 - 15
DIAGNOSIS AND TESTING (Continued)
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