Malfunctions of the engine cooling system, their causes and solutions
Cause of malfunction | Remedy |
The engine gets very hot | |
Low coolant level in expansion tank Faulty thermostat (thermostat valve stuck closed) Faulty water pump Radiator core clogged with dirt and insects Radiator pipes, hoses and engine cooling jacket clogged with scale and sludge The radiator fan does not turn on due to an open sensor circuit, sensor failure, relay, or fan motor Damage to the valve in the plug of the expansion tank (permanently open, causing the system to be at atmospheric pressure) | Add coolant to the expansion tank Replace thermostat Check water pump and replace if faulty Wash the outside of the radiator core Flush the engine cooling system and fill with fresh coolant Check and repair the radiator fan electric circuits. Replace sensor, relay, or radiator fan assembly as needed Replace expansion tank cap |
The engine overheats, cold air comes out of the heater | |
Excessive reduction in coolant level due to a leak or damage to the cylinder head gasket, causing vapor lock in the engine water jacket | Repair the coolant leak. Replace damaged cylinder head gasket |
The engine does not warm up to operating temperature for a long time, the thermal regime during movement is unstable | |
Faulty thermostat (thermostat valve stuck open) | Replace thermostat |
Constant drop in the coolant level in the expansion tank | |
Leaky radiator Expansion tank leaking Leakage of coolant through leaky connections of pipes and hoses Damaged water pump seal Damaged water pump housing gasket Insufficiently tightened cylinder head bolts (during a long stop on a cold engine, a coolant leak appears at the junction between the block head and the cylinder block; in addition, traces of coolant may appear in the engine oil) Heater radiator leaking (stove) | Replace heatsink Replace expansion tank Tighten hose clamps Replace water pump Replace water pump housing seal Tighten the cylinder head bolts to the required torque (see «Replacing the cylinder head gasket») Replace heater core (stove) |