Diagnostic Information and Procedures
Cooling System Diagnostic System Check (Cooling System Testing)Steps 1 - 5:
Steps 6 - 12:
Water Pump Test
1. Bring the engine up to normal operating temperature.
2. Squeeze the (upper) radiator inlet hose, while accelerating the engine speed. You should feel a pressure surge.
3. Inspect for a plugged vent hole in the water pump.
Radiator Test
1. Bring the engine up to normal operating temperature.
2. Turn the engine OFF.
- The radiator should feel hot along the left side.
- The radiator should feel warm along the right side.
- There should be an even temperature rise from the right to the left.
3. Cold spots indicate there are clogged sections of the radiator core.
Cooling System Diagnostic System Check (Exhaust Leaks and Noise)
Exhaust Leaks
1. Drain only enough coolant so that the level is just above the top of the cylinder head. Refer to Draining and Filling Cooling System.
Service and Repair
2. Disconnect the radiator inlet (upper) hose.
3. Remove the coolant thermostat.
Remove the accessory drive belt.
Notice: Allowing the drive belt tensioner to snap into the free position may result in damage to the tensioner.
4. Start the engine. Increase the engine speed (RPM) several times, while observing the coolant level. Any noticeable rise in the coolant level or the appearance of bubbles may show that exhaust gas is leaking into the cooling system.
Noise
Cooling system noise can be caused by restrictions to coolant flow. This can cause the coolant to boil at some localized point. Symptoms usually appear after extended idling or driving.
1. Possible symptoms are:
- The engine may make snapping or cracking noises.
- The radiator hoses may expand or collapse.
- The coolant heater hoses may vibrate or thump.
- The coolant heater core may gurgle or surge.
- The engine overheat lamp may or may not be illuminated.
2. Backflush the cooling system, then retest. Refer to Flushing.
Service and Repair
3. Use a mechanic's stethoscope to determine what areas are still affected.
4. Disassemble suspect components for further inspection and cleaning, as necessary.
5. Use the following diagnostic table in order to locate restrictions in the cooling system.
Engine Overheating
Steps 1 - 5:
Steps 6 - 12:
Steps 13 - 17:
Loss of Coolant
Steps 1 - 2:
Steps 3 - 9:
Steps 10 - 11:
Thermostat Diagnosis
For detailed thermostat diagnostic procedures. Refer to Cooling System Diagnostic System Check (Cooling System Testing) shown above.
Thermostat Test
The coolant thermostat can be tested using a temperature (tempil) stick. The temperature stick is a pencil like device. It has a wax material containing certain chemicals which melt at a given temperature. Temperature sticks can be used to determine a thermostats operating range by rubbing 87 °C (188 °F) and 97 °C (206 °F) sticks on the thermostat housing.
Tools Required
- J 24731-188 188 °F Tempilstick
- J 24731-206 206 °F Tempilstick
1. Use a tempilstick in order to find the opening and the closing temperatures of the coolant thermostat.
- J 24731-188 tempilstick melts at 87 °C (188 °F). The thermostat should begin to open.
- J 24731-206 tempilstick melts at 97 °C (206 °F). The thermostat should be fully open.
2. Replace the coolant thermostat if it does not operate properly between this temperature range.
Engine Fails To Reach Normal Operating Temp
Steps 1 - 4:
Fan Clutch Diagnosis
Noise
Sometimes fan noise is present under the following conditions:
- The clutch is engaged for maximum cooling.
- The noise is present the first 15 seconds to 1 minute after start-up. This condition occurs until the clutch can redistribute the silicone fluid to the normal disengaged operating condition (after settling 2 - 4 hours).
Fan noise or an excessive roar generally occurs under all high-speed conditions (2,500 RPM or higher) if the clutch assembly is locked up due to internal failure. If the fan cannot be rotated by hand or there is a rough grating feel as you turn the fan, replace the clutch.
Looseness
Inspect a loose fan assembly for wear. Replace a worn assembly as necessary. Under various temperatures, there is a visible lateral movement at the tip of the fan blade. Allow approximately 6.5 mm (1/4 in) maximum lateral movement measured at the fan tip. More movement is cause for replacement.
Silicone Fluid Leaks
Small fluid leaks around the bearing assembly will not affect the fan clutch operation. If the leakage appears excessive, replace the fan clutch.
Engine Overheating
Inspect for engine overheating as follows:
1. Start with a cool engine to ensure complete fan clutch disengagement.
2. If the fan/fan clutch assembly free-wheels with no drag (revolves more than five times when spun by hand), replace the fan clutch. Testing a fan clutch by holding the small hub with one hand while rotating the aluminum housing in a clockwise/counterclockwise motion will cause the clutch to free wheel. This is a normal condition when operated this way. It is not a test to determine replacement.
3. Position a thermometer between the radiator and the fan blades. Do this by inserting the thermometer sensor through one of the existing holes in the fan shroud, or by placing it between the radiator and the shroud.
4. With the thermometer in position, cover the radiator grille enough to induce a high engine temperature. Start the engine. Turn the air conditioning on. Run the engine at 2000 RPM.
5. It takes approximately 5 - 10 minutes for the temperature to become high enough to allow engagement of the fan clutch. This will be indicated by an increased in roar in the fan air noise. There also will be a drop in the temperature reading, from 3° - 15°C (5° - 15°F).
- If the clutch does not engage between 65° - 90°c (150° - 195°F), the fan clutch should be replaced. Be sure the fan clutch is disengaged at the start of the test.
- If the fan noise level is constantly high from the start of the test to 88°C (190°F), without any noticeable noise level increase or drop in temperature, the fan clutch must be replaced. To prevent engine overheating, discontinue the test, past a thermometer reading of 88°C (190°F).
6. As soon as the clutch engages, remove the radiator grille cover. Next turn off the air conditioning. This will assist in engine cooling. Run the engine at approximately 1500 RPM.
7. After several minutes, the fan clutch should disengage. There will be a reduction in fan speed with decreased fan noise. If the fan clutch fails to function as described, you must replace the fan clutch.