Stable operation of the internal combustion engine is impossible without efficient heat removal, for which the engine is responsible cooling-system. Many car owners mistakenly believe that it is enough to simply monitor the level of antifreeze, ignoring the physical condition of the working fluid under load. In fact, it is excessive or insufficient. pressure often causes overheating, rupture of pipes or even deformation of the cylinder head.
Checking this parameter allows you to identify hidden defects long before the car stands in the middle of the track with steam clubs from under the hood. In this article we will discuss in detail the physical principles of the circuit, diagnostic methods using special equipment and methods that allow you to assess the state of the system visually.
Understanding the processes that take place inside radiator and expansion-tankThis will help you avoid costly repairs. We will consider not only regular situations, but also critical scenarios when indicators go beyond the permissible limits.
Physical principles and the role of pressure in the circuit
The liquid in a closed circuit is heated to high temperatures, often exceeding 100 degrees Celsius. At atmospheric pressure, water boils at 100°C, but the engine temperature can reach 110-120°C and above. To prevent boiling and the formation of steam stoppers that disrupt circulation, the system is artificially sealed.
According to the laws of physics, increasing the pressure inside a closed volume leads to an increase in the boiling point of a liquid. That is why modern cars are used in cars. pressure-out, which can vary from 0.9 to 1.5 bar (atmospheres) depending on the design. This allows antifreeze to remain in a liquid state even under extreme heat loads.
The key element here is lid. It is not a simple plug, but a complex valve mechanism. Inside it, two spring valves are installed: one to maintain excessive pressure, the other to prevent the system from vacuuming when cooling.
If the tightness is broken, the boiling point decreases and the liquid turns into steam, which is compressed worse than the liquid, which leads to local overheating. Therefore, tightness control is, in fact, control of engine temperature.
Why not use water instead of antifreeze?
Water has a lower boiling point even under pressure and contains salts that form scale. Scaling worsens heat removal, which leads to an increase in pressure and rupture of the pipes.
Symptoms of leakage and pressure jumps
To determine problems with pressure can be not only with the help of tools, but also on indirect signs. A careful driver will notice changes in the vehicle’s behavior long before the emergency temperature lamp lights up.
One of the first signs is the appearance of a specific sweetish smell in the cabin or under the hood. This indicates that antifreeze vapors containing ethylene glycol are released through microcracks or loose compounds. You should also pay attention to the following symptoms:
- 🚗 The appearance of whitish plaque or oily spots at the junctions of pipes and radiator.
- 🚗 Frequent inclusion of the cooling fan even at moderate load on the engine.
- 🚗 Air bubbles in the expansion tank at idle speeds.
- 🚗 Deformation (inflatation) of the upper pipe of the radiator during warming up.
Especially dangerous phenomenon when after stopping the engine you hear gurgling or liquid is thrown through the valve in the lid. This suggests that pressure The system has critically exceeded the norm, and the valve cannot cope with the discharge of excess.
Preparation for Diagnostics: Tools and Safety
Before starting a direct inspection, it is necessary to observe elementary safety rules. Working with a hot coolant can lead to serious burns. It is strictly forbidden to open the cover of the expansion tank on the hot engine.
To conduct a high-quality diagnosis, you will need a minimum set of tools. The main instrument is gauge (pressure tester), which is often sold bundled with adapters for different types of covers. It may also be necessary to:
- 🔧 A set of clamps and plugs for temporary closure of the pipes.
- 🔧 A flashlight for visual inspection of hard-to-reach places.
- 🔧 Paper wipes to check for leaks.
- 🔧 Safety gloves and glasses.
It is important that the engine is completely cooled before the start of work. Ideally, at least 2-3 hours should pass from the last trip. This is necessary to equalize the pressure with the atmospheric and cool the metal.
Use a transparent hose worn over the neck of the expansion tank to safely drain the liquid when checking the valves, if active ejection suddenly begins.
Step-by-step pressure check with a manometer
The most accurate way to check the tightness of the circuit is to use a pump with a pressure gauge. This method allows you to simulate the working pressure and identify leaks that are not visible on visual inspection.
The inspection process begins with the removal of the expansion tank cover. Carefully inspect the sealing gum for cracks or bullies. If the rubber band has lost elasticity, tightness will not be ensured, and the device will show false results.
Then a pump adapter is installed on the neck of the tank. Smoothly pump the air, watching the arrow of the pressure gauge. Bring the pressure to the value indicated on the lid (usually 1.1-1.5 Bar), and stop pumping. Follow the readings for 2-3 minutes:
- If the arrow is standing still, the system is sealed.
- If the pressure drops slowly, look for the place of leakage (hisping, drops).
- If the pressure drops instantly - a breakdown of the gasket gasket or a serious crack.
Listen carefully during the pumping process. The characteristic sound of the outgoing air will help to localize the problem area. Often leaks are hidden under the nozzles or in the pump area.
☑️ Manometer test algorithm
⚠️ Never put pressures above 2.0 bar when checking old radiators. Thin honeycombs of old aluminum can not withstand the excessive load and burst, turning the diagnosis into expensive repairs.
Diagnosis without a pressure gauge: visual and indirect methods
What to do if there is no special pump at hand? There are several popular, but effective ways to assess the state of the system. They will not give exact figures in Bars, but will allow you to understand whether the circuit works in normal mode.
The first method is to check the operation of the valves of the cover. Remove the lid on the cold engine and shake it. You should hear a clear click of the bypass valve. If the valve is "stick", it must be washed or replaced.
The second method is to check the pipes on the warmed-up engine (with caution!). When the operating temperature is reached, the upper radiator tube should become hard as a stone. If it remains soft, then the pressure is not created, and the cover does not hold the vacuum or the valve is faulty.
Also pay attention to the color of the exhaust gases. If the exhaust pipe is thick white smoke with the smell of antifreeze, and the level of liquid falls, it is possible that the coolant enters the cylinders through a breakdown of the gasket. In this case, the pressure in the system will grow catastrophically quickly due to the gases breaking through.
A solid, bloated pipe on a warmed-up engine is a sign that the system is holding pressure. Too soft or too hard (stone) pipe is a sign of malfunction.
Pressure standards and fault table
Different engines have different pressure requirements in the system. For example, in modern turbocharged engines, the requirements are higher than in classical atmospheric units. Exceeding the norm leads to rupture, and a deficiency leads to boiling.
Below is a table that helps interpret symptoms and possible causes of abnormalities:
| Symptoms. | Probable cause | Risk |
|---|---|---|
| Pressure rises instantly | HBC gasket breakdown | Hydroshock, head deformation |
| Pressure's not holding. | Radiator crack or pipe | Overheating of the engine |
| The tubes shrink when they cool. | Faulty intake valve cover. | Crashing the tank, air suction |
| Continuous release of fluid | Faulty thermostat or pump | Loss of antifreeze, air traffic jam |
It is important to understand that critically For most passenger cars, the threshold is 1.5-1.6 bar. Exceeding this value usually leads to the operation of the emergency valve in the cover.
⚠️ Warning: If you find an oil emulsion (similar to mayonnaise) in the expansion tank, stop using immediately. This is a sign of oil getting into the antifreak, which requires serious engine repair.
Frequent Questions and Answers (FAQ)
Can I drive if the lid of the expansion tank does not hold pressure?
Long-term operation is not recommended. If the valve does not hold pressure, the antifreeze will boil at a lower temperature (about 100°C instead of 115-120°C). This will lead to constant overheating in traffic jams and accelerated engine wear.
What pressure should be in the cooling system to the cold?
On a completely cold engine, the pressure in the system should be equal to atmospheric pressure (0 Bar of excess pressure). If pressure is shown on the cold arrow of the pressure gauge, then there are problems with thermodynamics or residual gases in the system.
Why is the expansion tank inflating?
Bloating of the tank occurs when the pressure of the gases exceeds the strength of the plastic. The main reasons: valve failure in the lid (does not put off excess), breakdown of the gasket of the HBC (gases go to antifreeze) or severe overheating of the liquid.
How often should I change the antifreeze to preserve the properties?
Modern antifreezes (G12++, G13) last from 5 to 10 years or 150-250 thousand. mileage. However, it is recommended to check the level and condition of the liquid at each TO, approximately once in 15-20 thousand kilometers.
Can I add water to antifreeze during the test?
In short, you can only distilled water. But it reduces the boiling and freezing point of the mixture. For a full pressure check, this is not critical, but for operation it is better to use a ready-made concentrate or mixture.