One of my 955Ks had a scary looking crack in the main casting just beside the right side final drive. I always expected the machine to break in half, but it never did. Since it was cast iron, welding was pretty much out of the question. To help hold it together, I straddled the crack with a heavy metal plate and lots of bolts. To create that crack, someone may have dropped the machine off of a truck or trailer. They were just the right size to fit into the back of a dump truck, and maybe someone dumped it out too hard. Or they had a ripper on it and overdid it.
Although they were not as fast as an excavator is today, the 955s were great for digging basements. It was relatively easy to dig a very accurate hole. And one did not need much of a ramp; they could go up and down nearly vertical basement hole sides.
They did tend to run hot when the rad became blocked with dirt or other debris. Cleaning the exterior of the rad and reversing the blades, to alternately pull and push air, helped with that. It sounds as if your plan to clean the inside of the rad is a good one.