Main faults of the cooling system (Peugeot 406)

Overheat

• lack of coolant in the cooling system;
• thermostat is faulty;
• the radiator or its grille is dirty;
• the radiator fan is faulty;
• the temperature sensor is faulty;
• plugs in the cooling system;
• the expansion tank cap is faulty.

Low engine temperature

• thermostat is faulty;
• the temperature sensor is faulty;
• the radiator fan is faulty.

Coolant leaks

• damage to hoses or poor fastening with clamps;
• the cooling system radiator or heater radiator is leaky;
• the expansion tank cap is faulty;
• water pump seal leaking;
• boiling coolant due to overheating;
• plugs in the cooling system.

Internal coolant leak

• the cylinder head gasket is blown;
• cracks in the cylinder head or cylinder block.

Corrosion

• the coolant is not changed regularly;
• use of the wrong type of coolant.