Pinpoint Test C : The Engine Does Not Reach Operating Temperature
- Normal Operation and Fault Conditions
The engine cooling system maintains engine temperature during operation. Correct coolant flow through the engine, radiator and remainder of cooling system passages and components is essential to maintaining a correct engine temperature.
Engine coolant flows primarily from the engine to the radiator circuit and back to the coolant pump. Coolant is sent from the coolant pump through the engine block and cylinder heads. A separate circuit from the engine also feeds the heater core with coolant. The coolant pump circulates the coolant. The coolant thermostat is a control valve actuated by coolant temperature. When the thermostat is closed, coolant flow bypasses the radiator circuit and returns to the coolant pump. When the thermostat is opened, coolant flows through the radiator circuit in order to transfer engine generated heat to the outside air
Concerns of engine inability to reach normal operating temperature typically occur when the rate of coolant flow through some coolant circuits (radiator, heater core) is more than expected given the conditions. Heat is not allowed to build in the engine because a heat exchanger is removing too much heat, including the radiator, heater core and oil cooler. In addition, perceived concerns that the engine does not reach normal operating temperature can be related to a low coolant level or trapped air which does not allow for hot coolant to be available at the heater core, an inoperative climate control system, or for concerns perceived or related to an incorrect engine temperature gauge indication.
Possible Sources
- Low coolant level
- Thermostat
- Temperature gauge
- ECT Sensor (if equipped)
- WARNING: WARNING: Always allow the engine to cool before opening the cooling system. Do not unscrew the coolant pressure relief cap when the engine is operating or the cooling system is hot. The cooling system is under pressure; steam and hot liquid can come out forcefully when the cap is loosened slightly. Failure to follow these instructions may result in serious personal injury.
- C1 CARRY OUT INSPECTION AND VERIFICATION
- Carry out the Inspection and Verification procedure in this service information.
Were any concerns found?
Yes REPAIR as needed. No GO to C2 - C2 CHECK THE COOLANT LEVELNOTE: Allow the engine to cool before checking the coolant expansion tank.
- Visually check the engine coolant level in the coolant expansion tank
Is the engine coolant level within specification?
Yes GO to C3 No GO to Pinpoint Test A - C3 CHECK THE ENGINE TEMPERATURE
- Start the engine and allow the engine to idle for ten minutes.
- Feel the inlet heater hose and the upper radiator hose.
Are the upper radiator hose and the inlet heater hose cold?
Yes INSTALL a new thermostat. Refer to: Thermostat Housing . No The cooling system is operational. If an inoperative temperature gauge is suspected, CHECK the temperature gauge operation. Refer to: Instrumentation, Message Center and Warning Chimes . If an inoperative climate control system is suspected, CHECK the climate control system operation. For Electronic Manual Temperature Control (EMTC), For EATC, Refer to: Climate Control System - Vehicles With: Electronic Automatic Temperature Control (EATC) . CLEAR Diagnostic Trouble Codes (DTCs). If the DTC returns check for correct ECT sensor operation.