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Check Radiator Cap Thermostat Efficiency

Model: BMW Serie 5 E39 - Years 1995-2003
Part: Thermostat

The cap of the coolant reservoir plays a crucial role in the proper functioning of the cooling system: the cap is equipped with a valve that allows any air that may form in the system to escape (the number printed on or under the cap represents the pressure value at which the valve opens to release the air). A malfunction of this valve can cause excessive pressure buildup in the system, leading to a rupture of a hose or even the explosion of the reservoir (a common issue in the older E46 Series 3, especially gasoline models).

Updated on 10 February 2026 by ScegliAuto

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