D4D 22c Radiator flush.

I would run a flush before refilling with a good coolant. Should be no danger of damaging anything. The flush is achemical treatment, not abrasive.

I also had a problem with a D69U leaking after cleaning, but in my case, I had flushed the block out by running plain water in through the drain hole to flush up through the radiator while I had the top tank off rodding the core put. I apparently washed enough sludge out at the base of a couple sleeves that when I refilled it, water was running past the old o-rings at the bottom of the sleeves. A good dose of stop leak stopped the leak and I was able to use the tractor instead of overhauling it.

Most radiator flushes are pretty mild stuff these days. Most are some kind of citric acid treatment, but some are still a strong alkali that will need to be used with care. I had used a pint of muriatic acid in the D6 several years before when it first began running hot occasionally. That treatment did little to nothing for the overheating and I saw why when I took the top tank off later. Most of the flues in the radiator core were plugged. The chemical treatment could not help what it could not reach.

Just flush it with water. If it's operating normally, don't chance your luck.