Bought a new cooler from a reputable dealer.The cooler came capped but when you look inside there is a lot of flakey burnt flux inside.I ran solvent through it for a while and a lot of black crap came out.What is the normal procedure for cleaning here.I work in hydraulics so I could just hook it up to the bench and run lots of fluid through it but I would think it would be better if the oil is hot.