An engine probe system for monitoring a moving engine element. The probe system includes a capacitive sensor (1) including a sensing electrode (5) defining one of the electrodes of a capacitor and an output lead for coupling the sensing electrode (5) to data processing means for monitoring changes in the capacitance of the capacitor including the sensing electrode. The output lead includes a first conductor for connecting the sensing electrode to the data processing means, an insulation jacket surrounding the first conductor, and a flexible conduit (11) surrounding the insulation jacket and defining a fluid passage between the insulation jacket and the flexible conduit.