I would inspect with a mirror and flashlight and see if you can determine the problem before you disassemble anything. If it looks like it is leaking at the junction of hose and heater, just tighten the clamp and observe. Most often this is the issue as the hose shrinks over time. If is looks like it is the hose itself or within the heater, then you need to lower the coolant and remove/fix the offending part.
Kent
