I think if you can ensure they all thread together without a problem, it doesn’t need to be perfectly clean, but I suspect that will be difficult if there is melted filament in the threads at all

I see. I probably should have been more specific, sorry. If you do try torching the parts, be very careful with the heater block. They are usually aluminum, and can melt much more easily than the steel and brass parts.

Most nozzles and heat breaks have M6x1mm threads, so they’re pretty standard (double check yours specifically). Lightly chasing the heater block threads with a tap should clean out any gunk and ensure that your heatbreak and nozzle threads engage properly when you reassemble everything again, and that things get torqued together correctly.

If your heatbreak tube and nozzle don’t have any ptfe liners or anything, using a propane/butane torch to cook the PLA to carbon and wire-brushing it off is a fast way to get those threads clean.

If it’s all super gunked up, and you don’t wanna buy tools, you can generally buy just the heat break, heater block, and nozzle together pretty cheaply for most common hot end designs

Sort of. As the previous poster pointed out, you need to make sure it’s assembled in a way that the nozzle is seated against the heat break inside the heater block, not against the heater block itself. You’ll have to do a complete disassembly to clean it up properly, and you may need to run a tap through the heater block to clean the threads, but when you assemble it, make sure that you back the nozzle off a turn or so, assemble the hot end so that the heatbreak is bottomed out against the nozzle, then heat it all up and torque the nozzle up snugly to the heatbreak(quarter turn past touching is usually sufficient). There are YouTube vids that will demonstrate hotend assembly better than I can explain it, but solid nozzle to heatbreak seal is critical for preventing this

You have an incorrectly torqued connection between the heatbreak tube, nozzle, and heater block that is allowing filament to work its way past the threads and out the top/bottom. You’ll likely need to clean off what you can while hot in order to get it to a place where it can be disassembled and fully cleaned.

You may need to heat or even torch some of those parts clean, since there’s no generally available solvent for PLA to soak it off.

To prevent this, make sure you’re properly torquing those parts together according to the manufacturer’s instructions. Final torque is normally applied with the hotend empty and at temp.

Orientation of hot vs neutral