Late last fall we purchased a 7250 for an extra tractor but when working it hard it constantly wanted to overheat.  The exhaust temperature stayed within normal range but the coolant temp would run right to the red.  Now its in the shop and we just took the rad to a rad shop to have it boiled out and when they flow checked it before cleaning they said it was good.   We had it cleaned anyway and it flow tested the same after so now we're not sure to look at the water pump which seems tight or the head gasket or where to look.  The tractor doesn't use any coolant or engine oil.