I have old jotul 118 and after 3 months of burning I noticed it wasn't getting hot (above 300). After taking apart I found an inch of soot had settled on top plate above burn box. Also tee and 90 were 3/4 full of crusty creosote. After pulling stove pipe from flue tile I noticed that where pipe enters vertical section of 8x8 flue tile there are sap like globs of creosote attached to sides of tile. Haven't been on roof yet but I'm assuming that it is full all the way up. Will brushing get rid of this? Or how else do I clean it.