The cleaning door for our chimney is falling apart. Before we replace it, we want to track down the source of the creosote that sometimes dribbles out of the door. The door sits about four feet below where the stove's exhast pipe connects to the chimney. We clean the chimney regularly, at least three times each burning season, and from quick inspections with a mirror, we get very little creosote above the exhaust pipe. Could this be just cold air being drawn into the chimney around the broken door? And should we be concerned about the cracks in the mortar at the level of the chimney door? If we need professional repairs to the chimney, we want some knowledge about what our chimney truly needs. Any advice would be great.