Engine Overheats
WARNING:NEVER REMOVE THE PRESSURE RELIEF CAP UNDER ANY CONDITIONS WHILE THE ENGINE IS OPERATING. FAILURE TO FOLLOW THESE INSTRUCTIONS COULD RESULT IN DAMAGE TO THE COOLING SYSTEM OR ENGINE AND/OR PERSONAL INJURY. TO AVOID HAVING SCALDING HOT COOLANT OR STEAM BLOW OUT OF THE COOLING SYSTEM OR RADIATOR COOLANT RECOVERY RESERVOIR, USE EXTREME CARE WHEN REMOVING THE PRESSURE RELIEF CAP FROM A HOT COOLING SYSTEM OR RADIATOR COOLANT RECOVERY RESERVOIR. WAIT UNTIL THE ENGINE HAS COOLED, THEN WRAP A THICK CLOTH AROUND THE PRESSURE RELIEF CAP AND TURN IT SLOWLY UNTIL PRESSURE BEGINS TO RELEASE. STEP BACK WHILE THE PRESSURE IS RELEASED FROM THE COOLING SYSTEM. WHEN CERTAIN ALL PRESSURE HAS BEEN RELEASED, (STILL WITH A CLOTH) TURN AND REMOVE PRESSURE RELIEF CAP.
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DESCRIPTION
When investigating a concern of overheating or insufficient heater/defroster performance, the following tests should be performed:
1. Check and service any leaks in the:
- pressure relief cap.
- heater water hose (18472).
- radiator hoses.
- water hose connection gasket (8255).
- cylinder head (6049).
- water pump housing gasket (8507).
2. Check cold engine coolant level in radiator coolant recovery reservoir.
a. If level is below MIN mark, fill to MAX mark with an approved coolant. Add coolant to radiator coolant recovery reservoir.
b. If the cold coolant level in the radiator coolant recovery reservoir is sufficient, run the vehicle for 10 minutes with the pressure relief cap off and check for coolant circulation through the heater core and radiator. If the coolant drops below the MAX mark (after the engine has reached normal operating temperature), add coolant to the filler neck, until final coolant level, with engine warm is approximately 12 mm (0.5 inch) above MAX mark. Repeat the above procedure until all the air is purged from the engine cooling system.
c. When this procedure has been completed, feel the heater inlet and outlet hoses and the underside of the upper radiator hose (8260). The water thermostat (8575) should be removed only if these hoses are cold or if no coolant circulation is observed through the radiator after 10 minutes of operation.
WARNING: ALWAYS VENT THE EXHAUST TO THE OUTSIDE WHEN PERFORMING THIS TEST OR PERSONAL INJURY OR DEATH MAY OCCUR.
NOTE: Procedure is most accurate if performed indoors at less than 39°C (100°F) ambient air. This test may be performed with or without the hood (16612) open and with the engine warm or cold.
3. Allow engine to cool below operating temperature with the ignition switch in the OFF position, remove the Engine Coolant Temperature (ECT) sensor harness connector and connect the Rotunda Service Coolant Temperature Monitor Harness 007-00064 or equivalent between the powertrain control module (PCM)(12A650) and the engine coolant temperature sensor (ECT) (12A648). Attach Rotunda Digital Volt-Ohmmeter 014-00407 or equivalent to the monitor harness. Voltage values (0-5 volts) may now be monitored while the engine coolant temperature sensor retains its connection to the fuel charging wiring (9D930).
NOTE: A ground may be required for some applications.
4. Keep cooling fan motor and fan blade (8600) running during this test (high or low speed may be used). Two methods may be used to turn the cooling fan motor ON: disconnect the A/C clutch power supply and turn the climate control to A/C ON or disconnect the power supply to the cooling fan motor and supply 12 volts directly to the cooling fan motor from the battery (10653).
NOTE: Running test with the vehicle in gear or with the A/C clutch engaged (running) will cause improper diagnosis.
5. Place transaxle in PARK or NEUTRAL. Set the parking brake.
6. Start the engine and allow to idle throughout this test. Allow engine to run for two minutes and then record the engine coolant temperature sensor voltage. Now record engine coolant temperature sensor voltage every 60 seconds. When engine coolant temperature sensor voltage trend changes direction or only changes slightly (0.03 volt or less) from the previous reading, record this as the water thermostat opening voltage. Compare measurements to those specified on the following table:
7. If the opening voltage is greater than 0.79 volt (less than 80°C (176°F)), replace water thermostat.
NOTE: When this procedure has been completed, feel the heater inlet and outlet hoses and the underside of the upper radiator hose. The water thermostat should be removed only if these hoses are cold after 10 minutes of operation.
8. If the water thermostat opening voltage is LESS than 0.79 volt (greater than 80°C (176°F)), water thermostat is good and should not be replaced.