Liquid helium at temperatures below 2.172 K behaves like a quasi two‐component fluid due to the quantum effects becoming apparent at these low temperatures. The heat which is transported solely by the normal component generates temperature (second sound) shock waves and assists, above certain perturbation levels, the generation of superfluid vortex lines. The mutual friction between these vortex lines, present as a chaotic tangle, and the normal component affects strongly the fluid flow and hence heat transport, leading to a modification of the initially rectangular pulse shape, i.e. the appearance of a second temperature maximum which, close to the heater, can be much stronger than the temperature of the shock front.Experimental investigations of the overshot, made using especially developed temperature probes in the case of plane and axisymmetric heat pulses, will be presented. The results compare favourably with a semi‐phenomenological theoretical model.