Ok, my boiler was hooked up wrong for 2 years and wasnt maintaining a high enough temp and started to rust. It is now hooked up to maintain a 160 degree temp. When i did the complete cleaning the other day i noticed that there is alot of clumpy build up in the heat tubes. I used a wire brush on a drill to clean them but that didnt get it all out. Im wanting to use a more gressive cleaner but im afraid that since it started to rust fom being hooked up wrong i might cause a leak. Any thought on this? Is it repairable if i do get a leak?

The are elliptical scrapers. If your boiler tubes rust out, you may want to check the front page this site and read about JA's boiler.