u/EasyEastKY

We recently acquired a old military 5 ton that had been sitting for several years. We went through it changed all the filters and oil (oil looked good just very dark when drained no water, coolant, diesel or metal). After starting it and letting it idle for about 15-20 min we noticed a small peck, the peck very quickly turned into a knock and within seconds the motor locked.

Anyone have any ideas as to what could’ve caused this? Any tips on where to go from here, how likely can it be fixed?