Crank pin temperatures were measured and analyzed to find out practical method which can predict the engine bearing reliability. The measuring points were determined to be near the MOFT region and far from that by theoretical calculation. The effect of engine running condition, oil temperature, the change of oil circuit into bearing and crankshaft endplay on crank pin temperature were experimentally tested. The result obtained was as following. The crank pin temperature was dependent on oil film thickness and directly influenced by the change of test condition. Also, the length of the crankshaft endplay was confirmed to be critical to connecting rod bearing failure. In conclusion, we found that the measurement method of crank pin temperature can be used for predicting the engine bearing reliability.