Performed heater tune-up on a Goodman 90% gas furnace system. Checked the electrical, mechanical and performance systems of the unit. Cleared, cleaned, flushed and treated the drain line and cleaned the exterior of the furnace. I did find one of the furnace pvc exhaust pipes had a small crack where it connects at the furnace. This was causing a slow water leak into the furnace. I sealed the crack with silicone and verified it is leak free. No other issues were found. The system is operational at this time.