Acoustic liners are used to reduce fan noise in aircraft engine intakes but also in hot stream parts of the engine. To gain confidence in liner impedance models which are used for design it is important to make experimental tests under realistic conditions as possible. This paper present results of hot stream impedance eduction tests for single degree of freedom Helmholtz resonator liners with different configurations. These types of liners consist of a perforate top sheet backed by a honeycomb cavity to give a locally reacting wall treatment which can be characterized by an acoustic impedance. In the present case a number of different perforate sheet geometries were tested under varying grazing flow and temperature conditions. In some cases the liner test samples also included a thin layer of metallic foam. These types of liners are used for aircraft engine applications but are also of interest for IC-engine applications. It could be argued that the main effect of high temperatures is a change of medium properties such as: density, viscosity and speed of sound. If this is true the high temperature impedance could be predicted by scaling from the result at cold conditions. This is investigated in the paper by comparing measured results from liner impedance models available in the literature.