How to Boil Out a Radiatorby Allen Moore
When a radiator core plugs with deposits from hard water and/or old coolant, you can try to flush it out. Sometimes this works, sometimes it doesn't. In the event flushing doesn't do the trick, you can try to have the radiator rodded out, but in extreme cases the radiator core will need to spend some time in the boil-out tank before the rod will pass through the core tubes. This task requires a professional radiator repair shop, so don't try this at home.
Bend all the radiator core crimps away from the two radiator tanks using the radiator crimp tool. Use patience and caution to avoid cracking or breaking off a crimp.
Remove the tanks from the radiator core by hand. Peel the radiator tank gaskets off the tank and/or core, wherever it remains when the tank comes off, by hand.
Grab the radiator core with the tank tongs and lower it into the boil-out tank. Allow the radiator to sit in the tank for 12 to 24 hours to boil out properly.
Pull the radiator core out of the boil-out tank with the tank tongs. Be careful not to touch the tank until it's cooled off for an hour or so. Slide the radiator rod through each core tube to clear any leftover debris from the core.
Place the tank gaskets into the sealing grooves in the radiator tanks by hand. Crimp the tanks back onto the radiator core using the radiator crimp tool.