The invention relates to a glow plug for Diesel engines, comprising a housing, a heater rod, which is movable in the housing in axial direction and projects from the housing at a forward end, and a pressure measuring device for measuring a combustion chamber pressure exerted on the heater rod. It is provided according to the invention that a housing chamber is filled with a substance having or achieving liquid to paste-like consistency at temperatures occurring during operation and conducting heat generated by the heater rod to the housing.