NO.17 COOLING SYSTEM CONCERNS-OVERHEATING


17	COOLING SYSTEM CONCERNS -OVERHEATING
DESCRIPTION	The engine runs at higher than normal temperature/overheats.
POSSIBLE CAUSE	• Improper coolant level • Blown fuses • Coolant leakage • Excessive A/C system pressure • A/C system operation is improper • Improper water/anti-freeze mixture • Fans reverse rotation • Cooling air passage to radiator blockage • Poor radiator condition • Thermostat malfunction • Radiator hose damage • Improper or damaged radiator cap • Cooling fans are inoperative. • Coolant overflow system malfunction • Improper tension of drive belt • Drive belt damage • Eccentric shaft bypass valve malfunction (stuck closed)


STEP	INSPECTION	RESULTS	ACTION
1	Inspect the following: • Engine coolant level • Coolant leakage • Water and anti-freeze mixture • Radiator condition • Collapsed or restricted radiator hoses • Radiator pressure cap • Overflow system • Fan rotational direction • Cooling air passage to radiator • Fuses Are all the items normal?	Yes	Go to the next step.
1		No	Service if necessary. Repeat Step 1.
2	Connect the WDS or equivalent to the DLC-2. Retrieve any continuous memory, KOEO and KOER DTCs. Are there any DTCs displayed?	Yes	DTC is displayed: Go to the applicable DTC inspection. (See DTC TABLE.)
2		No	No DTC is displayed: Go to the next step.
3	Start the engine and run it at idle speed. Turn the A/C switch on. Does the A/C compressor engage?	Yes	Go to Step 5.
3		No	Inspect for the following and repair or replace if necessary: • Refrigerant charging amount • Open circuit between A/C relay and PCM terminal 5AA • Seized A/C magnetic clutch • A/C magnetic clutch malfunction If all the items are normal, go to the next step.
4	Connect the WDS or equivalent to the DLC-2. Access ACSW PID. Start the engine and run it at idle speed. Turn the A/C switch on. Does the ACSW PID read ON?	Yes	Go to the next step.
4		No	Inspect the following: • Refrigerant pressure switch operation • A/C switch is stuck open. • Open or short circuit between refrigerant pressure switch and PCM terminal 4W • Open circuit of blower motor fan switch and resistor (if blower motor does not operate) • Evaporator temperature sensor and A/C amplifier
5	Inspect the cooling fan control system operation. (See Cooling Fan Control System Inspection.) Does the cooling fan control system work properly?	Yes	Go to the next step.
5		No	Repair or replace the malfunctioning parts.
6	Is the drive belt normal? (See DRIVE BELT DEFLECTION/TENSION INSPECTION.)	Yes	Go to the next step.
6		No	Replace the drive belt. (See DRIVE BELT REPLACEMENT.)
7	Is there any leakage around the heater unit in the passenger compartment?	Yes	Inspect and service the heater for leakage.
7		No	Go to the next step.
8	Is there any leakage from coolant hoses and/or radiator?	Yes	Replace the malfunctioning part.
8	Is there any leakage from coolant hoses and/or radiator?	No	Go to the next step.
9	Cool down the engine. Remove the thermostat and inspect the operation. (See THERMOSTAT REMOVAL/INSTALLATION.) (See THERMOSTAT INSPECTION.) Is the thermostat normal?	Yes	Go to the next step.
9		No	Replace the thermostat.
10	Access the ECT PID. Inspect readings on both the ECT PID and the temperature gauge on the instrument cluster. Is the ECT PID indication the same as the temperature gauge readings?	Yes	Inspect the eccentric shaft bypass valve. (See Engine Workshop Manual.)
10		No	If the temperature gauge is in the normal range but the ECT PID is not the same as the temperature gauge reading, inspect the ECT sensor. (See ENGINE COOLANT TEMPERATURE (ECT) SENSOR INSPECTION.) If the temperature gauge on the instrument cluster indicates the cold range but the ECT PID is normal, inspect the temperature gauge and the sending unit. (See Water temperature gauge.)
11	Verify test results. • If normal, return to the diagnostic index to service any additional symptoms. • If the malfunction remains, inspect the related Service Information and perform the repair or diagnosis.