The increasing packing and power density in vehicles makes the thermal environment in the engine compartment more and more severe. A critical area in terms of radiation are the components facing the exhaust system.This paper shows the simulation methods applied at MAGNA STEYR finding hot spots and endangered parts when looking on the effects of radiation. The simulation runs in parallel to design, gives a reliable rating of variants and helps the designer to optimize his system. The influence of an exhaust manifold design change from double-walled to a single-walled on the steering system in a right hand drive vehicle is shown. This change was done due to cost reduction, but also resulted in additional costs for heat protection. The methods are applied in advance of the physical prototypes and help to find good measurement positions for the physical testing also.