The present work seeks to simulate the working conditions of journal bearings under heavy loading conditions and to determine experimentally the behaviour of journal bearings under various conditions. Tribological tests were performed on a test set up which simulated the journal bearing behaviour on a Detroit diesel engine (model 6V53, 2-stroke, w/air cooling). The tribological behaviour of crank shaft bearings of M113 A1-A2 armoured vehicles was investigated for various working parameters. Three different rotational speeds, three different running times, two different bearing loads, two bearing-shaft gaps and three different lubricant pressures were used. The effects of these parameters on the bearing temperature, oil temperature, surface roughness and mass change of the bush and bearing were investigated. For each experimental group, one of the parameters was taken as variable while the other parameters were kept constant. A simple beam type loading system was designed to simulate the force system created by the burning of the gases inside the cylinder. The results of this study show that the average surface roughness of bearing and of bushing does not vary with working conditions. The temperature of bearing and sump oil increased with the load. When the clearance was increased slightly the bearing temperature also increased, while the oil temperature decreased and roughness was reduced. The bearing mass increased at the highest speed of 3000 rpm while the mass of the bushing did not change with speed.