We bought an excavator from 1972 and are renovating it for private use. Brand is a manitu and it owns a Ford engine diesel. Can be its series 4000. Unfortunately, it oils out back and squirts like the plague. Unfortunately also at the crankcase ventilation. After trying around and testing we do not believe that it is the valves, but that because it has stood for a long time firm piston rings. How would you clean it. It is worth a try. We thought on 5W40 Buy and additive to it. Then run really warm and exchange. https://shop.liqui-moly.de/motor-clean-4.html Other ideas? Is not a truck engine very sensitive.