You say it's boiling over and leaking, this tells me that you have a seal leaking and a bad thermostat. Go to this sight
http://www.bunnomatic.com/pdfs/commercial/manuals/10784.0000.pdf it's a illustrated parts catalog so you can see where each of these parts are located inside the unit. Take the top off of the unit so that you can see the fill
basin. Now turn on the unit and add water. As you add the water, look all around for leaks. although I think they will not show up until the water gets hot and the Make sure you look real close under the tank for leaks. #3 re is pressure and heat built up. Scroll down to the diagram
that's labeled Tank and
Components. Look at part
labeled #9, #14, #16 and #17. You should find the leak at one or more of these parts. When the leak is found, you can try to order them from the number but I don't think they will sale parts. They only handel warranty. I order mt parts from
www.hfse.com Heritage Food Service Equipment. They sale all the
Bunn parts along with about every other part. Go to the sight and you can look up parts. Their number is on the sight, you will need to call them to order the parts. Good luck.