921521-6528 Tohatsu SCREW

Recommended Repairs
Low Coolant Level
Pressurized System: Hot coolant can cause serious burns. To open the cooling system filler cap, stop the engine and wait until the cooling system components are cool. Loosen the cooling system pressure cap slowly in order to relieve the pressure.
Table 1
Troubleshooting Test Steps Values Results
1. Check for leaks in the cooling system.
Note: Low coolant level can be the result of overheating rather than the cause.
A. Run the engine to operating temperature.
B. Inspect the cooling system for leaks.
Note: Check for the presence of coolant in the engine oil. This would indicate an internal coolant leak.
Coolant level
Result: There are no leaks in the cooling system.
Proceed to Test Step 2.
Result: A leak in the cooling system was found.
Add coolant, if necessary. If leaking is found, make the necessary repairs.
2. Air can enter the cooling system if the pressure cap is not operating properly. Check the operation of the pressure cap.
Note: If the coolant has been changed recently, ensure that the air has been purged from the cooling system. Refer to Systems Operation/Testing and Adjusting.
Note: The supply pressure to the water pump must be sufficient in order to prevent cavitation. Measure the supply pressure at the inlet to the water pump.
Pressure cap
Result: The operation of the pressure cap is OK.
Proceed to Test Step 3.
Result: The operation of the pressure cap is NOT OK.
Replace the pressure cap, if necessary.
3. The engine will overheat if the water pump is not operating properly. Measure the coolant pressure at the outlet of the water pump.
Water pump
Result: The water pump is operating properly.
Proceed to Test Step 4.
Result: The water pump is not operating properly.
Replace the water pump. Refer to the Disassembly and Assembly manual.
4. Check the shunt line for a restriction in the line.
Shunt line
Result: The shunt line does not have a restriction in the line.
Proceed to Test Step 5.
Result: The shunt line has a restriction in the line.
Remove the restriction or replace the shunt line.
5. If the engine is equipped with a radiator, check the fins of the radiator for obstructions.
Radiator
Result: The fins of the radiator does not have any obstructions.
Proceed to Test Step 6
Result: The fins of the radiator are obstructed.
If the radiator fins are obstructed, clean the fins.
6. Check the water temperature regulator for proper operation.
Water temperature regulator
Result: The water temperature regular is operating correctly.
Proceed to Test Step 7.
Result: The water temperature regulator is not operating correctly.
Replace the water temperature regulator. Refer to the Disassembly and Assembly Manual.
7. Compare the reading for the coolant temperature from the Caterpillar Electronic Technician (ET) to the reading for the coolant temperature from a mechanical gauge. The temperature should rise steadily as the engine is warmed. Ensure that the temperature is reasonable. Refer to Systems Operation/Testing and Adjusting.
Coolant temperature sensor
Result: The temperature is reasonable.
Proceed to Test Step 8.
Result: The temperature is not reasonable.
If the reading on Cat ET for the coolant temperature is not reasonable, troubleshoot the circuit and the coolant temperature sensor. Refer to the diagnostic functional test Troubleshooting, "Engine Temperature Sensor Open or Short Circuit - Test".
8. Check the back pressure of the exhaust system. Refer to the engine's Technical Marketing Information.
Back pressure
Result: The back pressure does not exceed the specifications of the engine.
STOP
Result: the back pressure exceeds the specifications for the engine.
Determine the cause of the excessive back pressure. Make the necessary repairs.
STOP