At the Institute for Material Science (IfW) of the Darmstadt University of Technology (TUD) extensive investigations have been undertaken since the fifties to investigate the action and the usability of corrosion inhibitors for coolant additives for combustion engines. The results of these research activities were published in a variety of world-widely recognized test specifications of the Forschungsvereinigung Verbrennungskraftmaschinen (FVV, Research Association Interal Combustion Engines). The presently applicable Test Specification FVV R443/1986  is currently revised in a research project with a view to adjusting it to the requirements made on coolant additives intended for use in modern-type and future combustion engines. The newly developed Modular Heat Test Apparatus (MHTA) promises essential advantages with regard to the assessment of the action and quality of coolant additives exposed to increased thermal stress and opens up new possibilities on the sector of testing coolant additives. After a brief historical look back, the technological details of the new test procedure will be illustrated. Subsequently, initial results will be presented and evaluated with respect to their practice-relevance and correlation with the presently applicable test specification.