[VWNate1]

As you said you have a four row core brass radiator it's a fairly simple thing to clean, use powdered citric acid mixed one pound of citric acid to each gallon of distilled water ~ mix this outside of the radiator and drive it a day or two, the coolant will turn dead black as it does it's thing, drain, flush and repeat until there's no clouds in the water / acid mix and no visible solder bloom .

This works with aluminum cooling systems too .

Remember to leave the heater's water valve wide open so it gets cleaned out too and never use tap water ! .