Radiator check (Mercedes-Benz Sprinter 903)

The cooling system operates under pressure. The radiator cap or expansion tank contains a spring that ensures the tightness of the system and opens it when the pressure rises to a certain level (the corresponding value is indicated on the lid). The increase in pressure due to the expansion of the coolant causes the boiling point to rise.



A special pump is used to check the plug. A cap is screwed onto it (figure 136, bottom), then pump until the valve opens under pressure. The pressure at which the valve opens is 1.4–1.5 bar if the plug is still new. A used plug must withstand a pressure of 1.3 to 1.4 bar. Otherwise, the plug must be replaced.

Using the same pump, you can check the tightness of the cooling system. It is screwed onto the filler neck through a special adapter (see figure 136). After this, you need to create a pressure of 1 bar, which when checked on the pressure gauge should be maintained for at least 5 minutes. If this does not happen, there are leaks in the cooling system, which are easier to detect when the system is under pressure.