Component Tests and General Diagnostics
Engine Cooling
Component Tests
Cooling System Pressure Test
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.
NOTE: Vehicles with a degas bottle system have the pressure relief cap on the degas bottle and no radiator cap.
1. Turn the engine OFF.
2. Check the engine coolant level. Adjust the coolant level as necessary.
3. Attach the Radiator/Heater Core Pressure Tester from the Pressure Test Kit to the degas bottle nipple and overflow hose. Install a pressure test pump to the quick-connect fitting of the test adapter.
4. NOTICE: Do not pressurize the cooling system beyond the maximum pressure listed in the Specifications table or cooling system components can be damaged.
NOTE: If the plunger of the pressure tester is pressed too fast, an erroneous pressure reading will result.
Slowly press the plunger of the pressure test pump until the pressure gauge reading stops increasing and note the highest pressure reading obtained. If the pressure reading exceeds the maximum cap pressure listed in the Specifications table, install a new pressure relief cap.
5. If the system does not hold pressure, remove the pressure relief cap and wash in clean water to dislodge all the foreign material from the gasket. Check the sealing surface in the filler neck of the degas bottle for nicks or cuts. Install the pressure relief cap.
6. Pressurize the engine cooling system as described in Step 4. Observe the gauge reading for approximately 2 minutes. Pressure should not drop during this time. If the pressure drops within this time, inspect for leaks and repair as necessary.
7. If no leaks are found and the pressure drops, the pressure relief cap may be leaking. Install a new pressure relief cap and retest the system.
8. If no leaks are found after a new pressure relief cap is installed, and the pressure drops, the leak may be internal to the radiator transmission cooler. Inspect the coolant for transmission fluid and the transmission fluid for coolant. Repair as necessary.
9. If there is no contamination of the coolant or transmission fluid, the leak may be internal to the engine. Inspect the coolant for engine oil and the engine oil for coolant. Refer to Engine System - General Information Testing and Inspection to diagnose the engine.
10. Release the system pressure by loosening the pressure relief cap. Check the coolant level and adjust as necessary.
Thermostat
A new thermostat should be installed only after the following tests and checks have been carried out:
- Pinpoint Test A, B or C
- Thermostat Visual Inspection
Thermostat Visual Inspection
1. Remove the thermostat.
2. Examine the thermostat for signs of damage including:
- Valve not fully seated (light visible through the valve)
- Foreign material lodged in the main valve
- Bent or broken frame or flange
- Bent or broken spring
- Bent or broken valve or valve stem
- Wax leaking from wax reservoir or a bulge in the reservoir
- Any other damage or distortion
3. NOTE: If no damage is found during the inspection, do not attempt to open the thermostat using hot water or other heat sources. This method is not an accurate means to test the function of the thermostat and may damage the thermostat.
If damage is found during the inspection, remove any foreign material or broken pieces and install a new thermostat.
4. If no damage is found during the inspection, continue troubleshooting the system concern. Go to the Symptom Chart for further instructions. Symptom Related Diagnostic Procedures
Radiator Leak Test, Removed From Vehicle
NOTICE: Never leak test an aluminum radiator in the same water that copper/brass radiators are tested in. Flux and caustic cleaners may be present in the cleaning tank and they will damage aluminum radiators.
NOTE: Always install plugs in the oil cooler fittings before leak testing or cleaning any radiator.
NOTE: Clean the radiator before leak testing to avoid contamination of tank.
Leak test the radiator in clean water with pressurized air to the maximum pressure listed in the Specifications.
Fan Clutch Test
1. Turn the engine OFF and wait until the fan comes to a complete stop.
2. Spin the fan blade by hand. A light resistance should be felt. If there is no resistance or very high resistance, the minimum and maximum fan speeds must be checked. For an electronically actuated fan clutch, refer to Computers and Control Systems. For a viscous fan clutch, carry out the following:
Fan Clutch Test - Minimum Speed Requirement
1. Use a suitable marker to mark the coolant pump pulley and one of the fan blades.
2. Make sure the A/C is OFF, if equipped.
3. WARNING: Do not operate the engine with the hood open until the fan blade has been examined for possible cracks and separation. A damaged fan can separate during operation. Failure to follow this instruction may result in serious personal injury.
Start the engine and run it at approximately 2,000 rpm for 5 minutes or until there is a noticeable reduction in fan noise to allow the fan clutch to go into disengaged mode.
4. Aim a laser photo tachometer at the coolant pump pulley. Run the engine to achieve 3,000 rpm at the coolant pump or fan pulley.
5. With the coolant pump pulley at 3,000 rpm, aim the laser photo tachometer at the fan blade. Monitor and record fan speed.
6. The fan blade speed must be less than the specified rpm at 3,000 rpm coolant pump pulley rpm. Refer to the Specifications table for correct fan speed.
7. Turn the engine OFF.
8. If the fan blade speed was greater than specified, install a new fan clutch.
Fan Clutch Test - Maximum Speed Requirement
1. Use a suitable marker to mark the coolant pump pulley and one of the fan blades.
2. Block off areas on each side of the radiator in the engine compartment, the front of the radiator grille and the bumper. Close the hood. This raises the temperature of the air striking the fan clutch and should cause the fan blade to operate at maximum speed.
3. Place the climate control function selector switch in the MAX A/C position and the blower motor switch in the HI position, if equipped.
4. WARNING: Do not operate the engine with the hood open until the fan blade has been examined for possible cracks and separation. A damaged fan can separate during operation. Failure to follow this instruction may result in serious personal injury.
NOTE: Do not open the hood to check the coolant pump pulley temperature. This lowers the temperature of the air reaching the fan clutch and voids the test. Aim the infrared thermometer through the wheel well or from under the vehicle.
Start the engine and run it at approximately 2,000 rpm until normal operating temperature has been achieved. Using an infrared thermometer, monitor the coolant pump pulley. Run the engine until the coolant pump pulley is at least 96°C (205°F).
5. NOTE: Do not open the hood to check the coolant pump pulley or fan blade speed. This lowers the temperature of the air reaching the fan clutch and voids the test. Aim the laser photo tachometer through the wheel well or from under the vehicle.
Aim a laser photo tachometer at the coolant pump pulley. Run the engine to achieve 3,000 rpm at the coolant pump pulley.
6. With the coolant pump pulley at 3,000 rpm, aim the laser photo tachometer at the fan blade. Monitor and record fan blade speed.
7. The fan blade speed must be greater than the specified rpm at 3,000 rpm coolant pump pulley rpm. Refer to the Specifications table for correct fan speed.
8. Open the hood and allow the engine to idle momentarily to lower engine temperature. Turn the engine off and remove the blocks from the radiator, grille and bumper.
9. If the fan blade speed is less than specified, install a new fan clutch.