1. The cooling system is under pressure. The cap of the expansion tank is equipped with a valve, which is designed so that it opens when the pressure rises by 0.8 atm. When the coolant expands, the pressure increases, which leads to an increase in the boiling point.
2. A special pump is required for testing. Place the pump on the cover and use it to open the valve. This must be done within the maximum allowable pressure. If this does not happen, replace the cap. Using the same pump, you can check the cooling system for leaks by placing it on the radiator filler neck or on the expansion tank. Set the pressure to 0.9 atm. and check that the pressure gauge indicates this pressure for at least 2 min. If this does not happen, there is a leak in the cooling system.