Abstract Numerical calculations based on finite difference approximations are carried out to assess the transient thermal response of the inlet and exhaust valves of a Tata-Mercedes, six cylinder, four stroke, water cooled diesel engine with a compression ratio of 19.5 and a rated power output of 110 hp at 3000 rpm for three different engine loadings. A detailed analysis has been given for estimating the boundary conditions of the inlet and exhaust valves of an internal combustion engine. The problem has been extended by applying a thin ceramic insulation coating of 2 mm thickness at the valve plate. The isothermal distribution in the valve bodies and the heat flow rates through the various cooling media for three different engine loadings have been depicted for each of the cases with and without insulation coating. The results indicate a reduction in heat loss through valves by use of an insulation coating on the valve plate.