Abstract: A sensor assembly, which may be part of an engine cooling system, senses a condition within an enclosed volume. The sensor assembly includes a mounting structure projecting from a wall of the enclosed volume. The mounting structure includes an opening extending from an exterior of the mounting structure towards the wall and at least one channel extending along an exterior of the mounting structure. The sensor assembly further includes a connector having a sensing portion for sensing the condition within the enclosed volume. A seal seals the enclosed volume at the extension of the connector through the opening. A retaining device has at least one attachment structure that is insertable into the at least one channel. The attachment structure engages the connector such that the connector is non-removable from the mounting structure. An associated method provides the sensor assembly.