Engine overheating is one of the most dangerous and unpredictable malfunctions. The result can be fright and easy repairs. But more often it ends up jamming, which is very expensive. The outcome depends on the cause and the driver. Often an overheated engine "dies" due to improper actions. From this material on the site ABS stations you will learn: why a serviceable engine does not overheat; signs of a malfunction; how to find and eliminate the cause; what to do and what not to do.
Why doesn't a good engine overheat?
The normal operating temperature of the engine is maintained by cooling and lubrication systems. The main task of the lubrication system is to reduce friction forces between parts. This is necessary so that as little useful energy as possible is spent on friction. The result is increased efficiency, power and torque. However, this is not all.
Reduced friction reduces heating of parts. This directly affects the temperature regime. Some parts, due to the presence of oil, do not heat up at all from friction. Heat is transferred to them from other parts that work near the combustion chambers.
Engine oil constantly circulates through the lubrication system from the sump, through the filter, oil pump, crankshaft, connecting rods, cylinder walls and gas distribution mechanism. It partially takes away the heat of the parts and, getting back into the pan, cools a little.
The main role in maintaining the operating temperature of the engine is played by the cooling system. Its key nodes:
- "Water jacket" of the engine - cavities, voids and channels around the cylinders and combustion chambers. Coolant circulates through them, removing excess heat.
- Pump - circulates the coolant. Driven by the crankshaft.
- Expansion tank - serves to fill the system with fluid, control its level and collect air.
- Temperature sensors - serves to operate the temperature gauge on the dashboard. There are also temperature sensors, the signals from which go to the electronic control unit. Thanks to them, the “brain understands” when the engine is cold, and it is necessary to increase the speed to accelerate warm-up. A separate sensor controls the fan of the main radiator.
- Stove radiator - located in the cabin and serves to heat the driver and passengers in winter. All of the listed nodes are a small circuit of the cooling system.
- The main radiator is located in the front of the car body, which allows it to be blown with an oncoming air flow when driving.
- Radiator fan - turns on when there is not enough air flow, or there is none at all (the car is in a traffic jam or moving too slowly). The small circuit of the cooling system plus these two nodes is a large circuit.
- The thermostat is a part that separates the small and large circuits of the cooling system. Until the liquid in the small circuit warms up, it is closed. When heated to a certain temperature, the thermostat opens slightly, bleeding some of the coolant into a large radiator for cooling. When the temperature drops, the thermostat closes.
When the cooling system is working and efficient, then everything works according to the following principle:
- The engine is cold - the thermostat is closed, the coolant circulates through the "water jacket" and through the stove radiator.
- The engine warmed up to operating temperature - the same thing. We can turn on the stove, it will blow warm air.
- The temperature is slightly higher than normal - the thermostat opens slightly, as a result of which part of the coolant enters the main radiator, and from there colder liquid returns to the small circuit. If the temperature has stabilized, the thermostat closes back.
- The temperature is much higher than normal - the thermostat opens completely, hot liquid from the small circuit enters the main radiator and is cooled by the oncoming air flow.
- not enough natural airflow for the radiator - the radiator fan sensor detects the critical temperature and turns it on.
The well-coordinated work of all nodes allows the engine to operate in a narrow temperature range, without overheating or overcooling. Thanks to this, maximum efficiency and fuel economy are achieved, the heater blows warm air, and details feel “comfortable”.
Signs of an engine overheating
An overheating engine can be judged by a number of signs. They are direct and indirect.
Direct signs of engine overheating
- The lamp on the panel of devices burns. Not available on all machines. If there is and glows, the engine has overheated. It looks like a thermometer with a scale that "floats" on two waves of liquid. Usually located in the area of coolant temperature gauge. The lamp is controlled by a separate sensor, which closes the circuit only when a certain temperature is exceeded.
- The temperature gauge needle went off scale. The pointer scale is usually divided into three areas - the norm, below the norm and the "red zone". If the arrow entered the "red zone" and continues to rise, then the cooling system can not cope.
- Puffs of white steam come out from under the hood. It indicates that the engine has overheated for a long time, the coolant has boiled, and the pressure has risen so much that it breaks out of the sealed cooling system through the weakest point (which it “chooses” itself).
The first two signs usually appear together. The third appears later if the driver has not responded to the arrow and the light bulb.
Indirect signs of engine overheating
- Lost power. It is decreasing for several reasons. The pistons expand and wedged, pierce the cylinder head gasket, jam the valves, piston rings scatter. There are other causes of power loss that are not related to overheating.
- Engine stalled. The reason is pistons jammed in the cylinders. This is due to the fact that pistons expand from heat faster than cylinder liners.
- Sound. When the coolant boils, there is a slight vibration with the corresponding sounds. You can also hear hissing. The last sound of overheating is metallic, percussive, with a crunch and rattle. Engine jammed.
- A puddle of coolant. Depressurization of the cooling system.
Causes of engine overheating
There are many possible reasons for an engine overheating. Here are many 10 pieces.
Low coolant level
The coolant level is controlled by two marks on the expansion tank. It fluctuates between these two marks depending on the temperature of the engine and the environment. With the onset of winter and severe frosts, you can notice a sharp decrease in the level on a cold engine. This is because the antifreeze has decreased in volume. As the engine warms up, the level rises to normal.
If the coolant level is always below the minimum mark, this may be the cause of overheating. When fluid is not visible at all in the expansion tank, temperature problems are guaranteed. Therefore, the first step is to assess the coolant level.
Thermostat stuck closed
Coolant from the small circuit cannot enter the main radiator. It first circulates in a small circuit with a normal temperature, then signs of overheating begin to appear. In winter, when the heater is on, overheating may occur later, as a lot of heat enters the car interior. In summer, a malfunction causes the engine to overheat within a few minutes after reaching operating temperature.
Checking the thermostat for jamming is easy. without removing it from the car. To do this, it is necessary to estimate the temperature of the branch pipe in the large circuit. If the engine starts to overheat, and the pipe between the thermostat and the main radiator is cold, then the thermostat is stuck in the closed position. You can verify this "in boiling water." Place the thermostat in a container of water and boil it on the stove. If the water boils and the thermostat doesn't open, it's broken.
Thermostat opens too late
The problem occurs when the thermostat is worn out or when it is not fitted correctly. Different engines are designed for their operating temperature, under which thermostats are made. If for your car the norm is +95°C, and the thermostat starts to open at +105°C, this is overheating.
The temperature for which the thermostat is designed is on its body. The indicator can be checked at home. Practically.
Take a metal container. Pour water and place a thermostat with a thermometer in it. The thermometer and thermostat should not touch the walls and bottom of the container. But they must be completely immersed in water. Heat it up, and watch at what temperature the valve starts to open, and then opens completely. Compare the received data with the specifications of your vehicle.
Radiator not blowing
The main radiator does not work efficiently if its cells are clogged with dirt, dust, insects and other debris. Overheating of the engine is observed even when driving on the highway. What shouldn't be. The fan often works, the arrow goes off scale and, possibly, the control lamp lights up.
To eliminate this cause of engine overheating, you need to carefully clean the radiator from dirt. This is not easy to do. It is necessary to clean very carefully, since the thin parts of the radiator can easily be bent and damaged. For cleaning, buy a special tool in a car shop. Usually it is an aerosol foam in a can. Treat the radiator liberally on both sides. Wait a bit. Then rinse off the remaining product with running water.
Attention! Cleaning a hot radiator is strongly discouraged.
Radiator fan does not turn on
The radiator fan should only be turned on at high engine loads, at low speeds (1st or 2nd gears), and also when the engine is running at a standstill. When driving at medium and high speed, there must be enough oncoming air flow to maintain normal temperature.
If the engine only overheats when the fan is supposed to run, it probably won't turn on. There are several reasons. The sensor that monitors the critical temperature and turns on the fan has failed. Open or poor contact in the fan power circuit. The fan is broken.
There are several ways to check the fan. Measure the temperature of the cooling system. Does the fan turn on at a critical temperature? In the specifications of the car, you can find the temperatures at which the fan should turn on.
If the fan does not turn on, then check the sensor and the fan motor.
A serviceable engine is designed for quite serious loads:
- long climb uphill;
- driving with a trailer;
- car towing;
- driving on a bad road;
- driving at high speeds.
If the cooling system is faulty or inefficient, the engine overheats at the slightest load.
Coolant pump not working
For the cooling system, pump failure means the same thing as cardiac arrest for a person. For some time, antifreeze can still remove excess heat from parts, circulating naturally (as in gravity-type heating systems). But it won't last long. Coolant circulation in the system is a key factor. If it stops, the temperature will rise very quickly. Even if the engine is not loaded, and the radiator is normally blown by air.
Problems with the engine lubrication system
The lubrication system plays an important role in maintaining the operating temperature of the engine. If there are problems, then the cooling system will not cope with overheating. She will not have time to take away so much heat.
Let's consider the main problems. Insufficient engine oil level. Checked with a dipstick. Do this every day before leaving the garage or parking lot for the first time. The lubrication system can be clogged with deposits in places, due to which oil does not flow to all rubbing parts. To fix the problem, flush the engine and change the oil. There may also be low pressure in the lubrication system. Leads to poor lubrication and heat dissipation. Especially from those engine parts that are higher. Low pressure is indicated by a warning lamp that, on a serviceable engine, lights up when the ignition is turned on, and goes out a few moments after starting. If it does not go out, or lights up while driving, overheating is guaranteed.
Something is holding the car
A wedged wheel bearing, flat wheels, faulty brake pads, clutch, or incorrect wheel alignment can “slow down” your car.
A sign that something is “holding” the car is an extremely bad roll. You can check it by feeling in neutral gear and on a flat road, having previously accelerated to a speed of 30-40 km/h.
Additional Causes of Engine Overheating
The following reasons are less common:
- movement in mountainous areas much higher than sea level;
- air conditioner malfunction;
- wear of automatic transmission;
- tuning the front of the car, due to which the radiator was closed;
- punched cylinder head gasket;
- abnormal heat outside;
- low-quality coolant;
- dirt and scale in the cooling system.
Engine overheated - what to do?
Stop the car and turn off the engine first. It is impossible to continue moving until the cause is clarified and eliminated. If overheating is not critical, turn on the heater in the cabin at full power. If it is safe to do so, turn off the engine first before stopping. This will slightly reduce the temperature due to the oncoming air flow.
You can only move on under certain conditions. For example, if the engine does not overheat quickly. In order not to aggravate the situation, it is recommended to use the services of a tow truck or a tow rope.
Attention! Bad advice! Sometimes, when overheating on the road, it is recommended not to turn off the engine in any case. This is justified by the fact that when the engine is running, the pump continues to function. This recommendation is rather dangerous. You may not know if the pump is working or has already failed. If it is broken, then such actions will only increase the losses. It is better to stop the engine immediately.
Wrong actions when the engine overheats
You can not keep moving, hoping for luck.
Do not open the hood when puffs of steam escape from under it. This often results in severe burns. Remember that when the coolant boils, it is not smoke that escapes from under the hood, but white steam. Therefore, it is not worth rushing to use a fire extinguisher. The sign of a fire is black smoke, not white.
Do not pour cold water on the engine. This is guaranteed to end with deformations of the block, head, and the formation of cracks.
Do not add coolant or water when the engine is "boiling". Wait until it cools down a bit.