I bought my 580 B with a blown head gasket, that has been repaired . Now what is the best way to get the oil residue out of the radiator? it is a 580 B diesel.
Cascade dish washing soap in the radiator. It's non foaming. That's what I used in a D8R when the oil cooler went bad. Then I put some Dawn dishwashing soap in and really flushed it.
Another vote for Cascade, or TBH any powder detergent designed for dishwashing machines, simply because it's non-foaming. Don't be frightened to get the engine really hot and be warned it make take you a couple of attempts before the water you drain out is clean & completely free of oil. Flush it a couple of times with clean water after that then fill with appropriate coolant.