Typical faults in the cooling system include leaks and insufficient engine cooling efficiency. The first occurs due to damage to the hoses and their connections, the water pump seal, damage to the gaskets, cracks, and the second - due to a faulty fan, breakdowns of the water pump, a faulty thermostat, external and internal contamination of the radiator as a result of scale formation.
Signs of a faulty cooling system include engine overheating and boiling coolant in the radiator, unless they are the result of prolonged and heavy engine load or improper adjustment of the ignition or fuel system.
Thermostat Troubleshooting Algorithm
Note: An indicator pencil is similar to a regular pencil and contains a material with certain chemical additives that provide a given melting point. By marking the thermostat housing with a pencil at 82°C and 95°C, you can check the thermostat operating temperature. These marks should melt when the coolant temperature reaches 82°C and 95°C, respectively. These temperatures determine the thermostat's operating range. Therefore, if the circulation does not occur as shown in the diagram, it means that the thermostat may be faulty.
| Sign of malfunction | Possible reasons | Solution |
| 1 | 2 | 3 |
| The engine gets very hot | Low coolant level | Add coolant |
| Low concentration of antifreeze in the coolant | Check the concentration of antifreeze | |
| The radiator tubes and fins are clogged from the outside with insects, leaves, etc. | Clean the radiator | |
| The radiator cooling pipes are clogged | Clean the radiator from foreign materials (rust, dirt, sand, etc.) | |
| Coolant leaks through leaks in hose connections, pump, heater, thermostat housing, radiator, expansion tank, drain cock, or through the cylinder head gasket | Fix leaks and make necessary repairs | |
| Thermostat failure | Check the thermostat for proper operation and replace it if necessary | |
| Failure of the electric / electric fan/s | Check that the electric fan/s is working properly and replace it if necessary | |
| Radiator hoses are clogged or worn out | Replace the radiator hoses | |
| Water pump malfunction | Replace the water pump | |
| Overflow of the expansion tank and exhaust gas leaks into the cooling system due to: - damage to the cylinder head - damage to the cylinder head gasket | Replace the cylinder head; replace the cylinder head gasket | |
| Defective tank cap | Replace the expansion tank cap | |
| Cracks in the cylinder head or block, blockage of cooling jacket channels | Repair the cylinder head or block | |
| Engine overload due to improper driving style when: - high engine speed without load -driving in low gear for a long time - moving at very high speed | Drive your car correctly | |
| Incorrect operation of the power unit | Repair the engine | |
| The wheels and tires are of the wrong size | Install the correct tires and wheels | |
| brakes "grabbing" | Check the brakes | |
| Air flow is restricted due to: - the holes in the bumper are clogged - there are foreign objects in front of the radiator grille - the capacitor is clogged | Clear the holes in the bumper Clear space in front of the radiator grille | |
| Low coolant level | Radiator leaks | Inspect the radiator and fix any leaks |
| Leaks in the expansion tank or hose | Replace the expansion tank or hose | |
| Loose or damaged radiator or heater hoses | Re-install hose connections, replace hoses or clamps | |
| Destruction of water pump seals | Replace the water pump seals | |
| Incorrect tightening of cylinder head bolts | Tighten the cylinder head bolts to the specified torque. Replace the cylinder head gasket if necessary | |
| Leaks through the intake manifold, cylinder head gasket, cylinder block plug, heater core, heater valve, radiator cap | Eliminate leaks, repair or replace defective parts and components | |
| The engine does not warm up to normal temperature. Cold air supply from the heater | The thermostat valve is stuck open or the thermostat is the wrong type | Replace Thermostat |
| The coolant level is below the "MIN" mark | Add coolant |
[The source of the article is on the website: NISSANBOOK]