Service Manual

4.12
COOLING SYSTEM
THERMOSTAT
Removal (Engine Installed)
1. Drain coolant so the coolant level is below the thermostat
housing (see “Coolant Drain / Radiator Removal”).
2. Remove the (2) screws from the rear portion of the air box.
3. Locate the thermostat housing on the left side of the valve
cover next to the fuel rail.
4. Remove the (2) screws and lift the housing up far enough
to remove the thermostat with the coolant line still attached.
Installation
1. Install the thermostat, thermostat cover, and the (2) screws.
Torque screws to specification.
2. If servicing while the engine is in the vehicle, perform the
“Cooling System Bleeding Procedure”.
TROUBLESHOOTING
Cooling System
Overheating
• Low coolant level
• Air in cooling system
• Wrong type/mix of coolant
• Faulty pressure cap or system leaks
• Restricted system (mud or debris in radiator fins
causing restriction to air flow, passages blocked in
radiator, lines, pump, or water jacket, accident damage)
• Lean mixture (fuel system restriction)
• Fuel pump output weak
• Electrical malfunction
• Water pump failure/ Loose impeller
• Engine Coolant Temperature Sensor failure
• Cooling fan inoperative or turning too slowly (perform
current draw test)
• Low oil level
• Spark plug incorrect heat range
• Faulty hot lamp circuit
• Thermostat stuck closed or not opening completely
Temperature Too Low
• Thermostat stuck open
Leak at Water Pump Weep Hole
• Faulty water pump mechanical seal
• Worn pump shaft or pump shaft bearing
= T
Thermostat Housing Screws:
89 in. lbs. (10 Nm)
Thermostat
Shown with air box
removed for clarity.
Housing
89 in. lbs.
(10 Nm)