Abstract: In internal combustion engines, one of the most critical factors in engine efficiency is the sealing unit. All mating surfaces should be seal very well by using gasket assembly to keep the closed cycle system during operation in different environmental conditions and loads operation. The problems of inadequate and non-suitable gasket selection and also the leakage problems due to the non-uniform load distribution will diminish the engine pressure and minimize the engine performance and finally to damage the components. The main objectives of this research are to find out the most effecting factors on the gasket unit performance by analysis and simulation method. Finite element method under (Abaqus/CAE) code has different solutions for such types of nonlinear behaviour. Modelling of these complex nonlinear behaviour’s like loading along contact paths, nonlinear elasticity and plastic distortion are available in Abaqus. It can simplify the components and in same time the essential elements properties will maintain the nonlinear response. In this research, the completed assembly model of gasket sealing unit is consist of upper aluminium manifold cover, two bolts, lower manifold block, paste gasket with silicone bead and base steel plate. These complex geometric parts with different engineering materials are subject to large amount of compound strains and due to the nature of materials used in engine gasket, all compressive response will be nonlinear. This nonlinearity will add more challenge on the modelling and analysis of the whole continuum model. As a results, it’s found that the effects of thermal expansion and engine pressure will cause some distortion in the assembly unit and will rise the tighten bolts force to maximum values. Also, the deformation or non-uniform in sealing cover will leads to down the engine performance. It’s concluded that the stress distribution will be not uniform due to loads and differences in distortion rate on each individual part. Also, the clamping forces distribution need to be increase without exceeding the strength of each part.