I have a cast iron steam boiler to heat my home. the stam has been leaking from a metal plate on the side of the boiler held on by 6 metal bolts. Two of the bolts appear to be rusted. What is the best way to remove these bolts without damaging the cast iron boiler? Should I run the boiler before attempting to remove the bolts? Will the heated boiler expand allowing easier removal of the bolts? Thank you for your immediate response.