In this paper, the thermal performance of a liquid cooling block designed for automotive lighting components integrated with high power Light Emitting Diode (LED) was investigated, numerically and experimentally. Single and multi-chip on the printed circuit board (PCB) were selected to get comparative numerical results in view of temperature differences on PCB surfaces for automotive lighting systems. In the numerical simulations, three-dimensional Computational Fluid Dynamics (CFD) model with natural convection effects was developed for predicting temperature distributions of PCB surfaces. For this purpose, the single and multi 5-cell high power LED lighting system with cooling block design were modeled. On the other hand, the effect of the aspect ratio of cooling channel and block material on the thermal performance of circuit boards with single and multi-chip was also investigated numerically due to needing for weight reduction for automotive lighting applications. From the results, higher temperature gradients were measured and predicted near the LED chip due to the heat production of LEDs. Block material had little impact on the LED temperature but using different materials aid to reduce block weight for automotive application. From the comparison of the numerical data obtained for each PCB, the LED junction temperature was similar therefore same cooling block design can also be used for multi-LED chip applications for Automotive Lighting Systems. This Multi LED design using with liquid cooling block gives more opportunities for future head and rear lamp applications of vehicles.