[Mark]

This answer is based on gut feel and may bear no resemblance to a correct answer.

In noticing the dirt, exhaust stains, and road film on the perforated panels on my coach at the radiator it is clear that what is on the stainless panels is also drawn into and through the radiator. But as heavy as the radiators on our coaches are, they are quite fragile and cannot take much abuse, especially the cooling fins.

I know from the literature and experience that Simple Green has a product suitable for aviation use. That version of Simple Green will not corrode or eat into the various metals but it is an excellent solvent that dissolves oily films and loosens dirt. If I sense the radiator will benefit from a cleaning I spray liberal amounts of that Simple Green on the radiator fins and tubes, give it a while to loosen or dissolve the crud and using a gentle water flow from a garden hose I flush it clean. I try to do it from both sides in both directions, but because of the fan shroud it is not possible to do complete coverage from the engine side.

The most important preventive maintenance for a radiator however is coolant changes to the specified schedule and by maintaining the chemistry of the coolant if necessary. The radiators on the Series 60 engines do not seem to be as adversely affected by coolant issues, but the 2 stroke engines such as the 8V92 seemed to plug radiators even with good coolant maintenance.