| Be very carefull using a pressure washer as you will bend all the fins with the blast.
I have a few NC/RC30's and these are the pits to keep clean on the lower rad, anyway what i do is simply remove the rads, leave to soak for a few days in a bucket of water, then using a small cable tie proceed to poke the worst of the mud out and straighten any bent fins, then when the mrs isnt looking throw it in the dishwasher, and give it a couple of cycles turning it over each time. then enjoy your new spankly clean radiator. | 
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