Pressurization system (10, 100) of a cooling circuit of a utility vehicle, comprising: a coolant tank, a pressure source, this latter being a common pressure circuit of said vehicle, and a pressurization line connecting said pressure source and the coolant tank for pressurizing the coolant tank, said pressurization line comprising a first pressure limiting valve which is a pressure reducing valve for reducing the pressure supplied to the coolant tank to a preset first pressure, a solenoid valve arranged in line with the first pressure limiting valve and control means for controlling the operation state of the solenoid valve dependent on an operation state of the vehicle, wherein the solenoid valve is disposed between the first pressure limiting valve and the coolant tank and being a 3/2-way valve comprising a first port, a second port and a third port, wherein the first port communicates with the first pressure limiting valve,the second port communicates with the coolant tank,and the third port communicates with a second pressure limiting valve (40, 104), wherein the first port and second port are flow connected in the activated state of the solenoid valve to connect the coolant tank with the first pressure limiting valve, and the third port and second port are flow connected in the deactivated state of the solenoid valve to connect the coolant tank with the second pressure limiting valve (40, 104), said second pressure limiting valve (40, 104) limiting the pressure of said coolant tank at a preset second pressure which is different with respect to said first pressure, said second pressure being lower with respect to said first pressure, said solenoid valve is activated either if both first and second conditions and are fulfilled and the third condition is fulfilled or if the fourth condition is fulfilled, wherein • a first condition is fulfilled if the vehicle ignition is activated; • a second condition is fulfilled if the front hatch of the vehicle is closed; • a third condition is fulfilled if the water pump of the vehicle is activated and/or in a predetermined operation state; and • a fourth condition is fulfilled if a temperature within the cooling system is higher than a predetermined temperature value. a coolant tank, a pressure source, this latter being a common pressure circuit of said vehicle, and a pressurization line connecting said pressure source and the coolant tank for pressurizing the coolant tank, said pressurization line comprising a first pressure limiting valve which is a pressure reducing valve for reducing the pressure supplied to the coolant tank to a preset first pressure, a solenoid valve arranged in line with the first pressure limiting valve and control means for controlling the operation state of the solenoid valve dependent on an operation state of the vehicle, wherein the solenoid valve is disposed between the first pressure limiting valve and the coolant tank and being a 3/2-way valve comprising a first port, a second port and a third port, wherein the first port communicates with the first pressure limiting valve,the second port communicates with the coolant tank,and the third port communicates with a second pressure limiting valve (40, 104), wherein the first port and second port are flow connected in the activated state of the solenoid valve to connect the coolant tank with the first pressure limiting valve, and the third port and second port are flow connected in the deactivated state of the solenoid valve to connect the coolant tank with the second pressure limiting valve (40, 104), said second pressure limiting valve (40, 104) limiting the pressure of said coolant tank at a preset second pressure which is different with respect to said first pressure, said second pressure being lower with respect to said first pressure, said solenoid valve is activated either if both first and second conditions and are fulfilled and the third condition is fulfilled or if the fourth condition is fulfilled, wherein • a first condition is fulfilled if the vehicle ignition is activated; • a second condition is fulfilled if the front hatch of the vehicle is closed; • a third condition is fulfilled if the water pump of the vehicle is activated and/or in a predetermined operation state; and • a fourth condition is fulfilled if a temperature within the cooling system is higher than a predetermined temperature value. • a first condition is fulfilled if the vehicle ignition is activated; • a second condition is fulfilled if the front hatch of the vehicle is closed; • a third condition is fulfilled if the water pump of the vehicle is activated and/or in a predetermined operation state; and • a fourth condition is fulfilled if a temperature within the cooling system is higher than a predetermined temperature value.