Recently, prediction of cylinder head temperature, using simulation techniques is one of interested tool for engineers. The main aim of this paper work is to predict the temperature field and mechanism of heat transfer prediction along cylinder head of diesel engines.Numerical analysis of conjugate heat transfer (CHT) between cylinder head and coolant was carried out. For the analysis of a six cylinder, four cylinder, three cylinder, and two cylinder stationary diesel engines for different BMEP were taken. Simulation model was prepared and solved using commercial CFD software (STARCCM+ 9.O2) in two steps i.e. flow and Conjugate Heat transfer simulation. Flow simulation predicts flow distribution and its flow velocities along with its variation with respect to cylinder location and channel dimensions. Cylinder head is then used for further analysis where flow and heat transfer is solved simultaneously using CHT (conjugate heat transfer) simulation technique. It predicts temperature distribution of the cylinder head bottom deck, exhaust port, valve bridge region and other critical locations. The input data for heat transfer coefficient values are obtained from analytical methods. This study was performed at various loads to examine the trends in temperatures and provide an input to the estimation of the cylinder head life based on field operating conditions. From these trends lines, correlations of temperature with BMEP are developed. Also efforts extended, to measure the temperature experimentally at rated load at various critical locations by providing templug. These values of temperatures are used to validate the numerical predicated temperatures at rated load. It found good agreements with experimental results. From the predicated temperature field nucleate boiling mechanism is proposed. Temperature prediction helps to locate point wise detection of hot spots along cylinder head; causes thermal stresses, responsible for engine failure.