Melted plastic oozing from the side of the nozzle

Hello,
Today I noticed that my (bowden) extruder was skipping on the filament sometimes.

Then I had a look at the nozzle and noticed black, melted plastic coming out from the side (or better, the gap) where the nozzle is screwed into the heater block.
First I thought it might have been there for a longer time and cleaned it off, but then half an hour later I checked again, and again a little blob of black plastic was there, on the side of the nozzle (the upper part, where you can put a wrench and turn it).

The print is still going fine though.

Also, for your info: I'm printing transparent / blue now, but have printed black in the past (a few months back) and printed in red yesterday. Always PLA.
I have no idea if a part of the black or red filament is somehow stuck in there and if it is, why it comes out from the side??
Later, I'll try to unscrew the nozzle while hot and have a look.

If I find "something", what would be the best way to clean?

My theory is that something's sitting in there and (no idea why) coming out from the side. And since it takes up space in the heater, my transparent filament has issues coming out sometimes, causing the slipping of the extruder gear.

Thank you in advance!
Dave

The main culprit for this is that the nozzle is not screwed in enough to create a seal between the nozzle and the heatbreak tube

When you re-assemble the hotend, screw the nozzle all the way in and then unscrew about 1/2 a turn, now crew the heatbreak in until it touches the nozzle.
Now heat the hotend up and re-tighten the nozzle so that it is completely sealed.

Okay!
I actually did that but either the whole procedure with temp. on (or everything with temperature off, I don't remember).
So should I disassemble it while cold and tighten the nozzle (last step) when hot?
Also, do any cleaning or not?
I'd also have the option to take a new nozzle (and / or heater block, but no heatbrake) as I have those parts on hand.
Thanks already!

Quote
obewan
The main culprit for this is that the nozzle is not screwed in enough to create a seal between the nozzle and the heatbreak tube

When you re-assemble the hotend, screw the nozzle all the way in and then unscrew about 1/2 a turn, now crew the heatbreak in until it touches the nozzle.
Now heat the hotend up and re-tighten the nozzle so that it is completely sealed.

Hello!
I disassembled everything and cleaned the different components individually with a metal brush after heating them with a heatgun.
Then I reassembled it (cold):
1) Screw in nozzle into the heater block all the way
2) Unscrew 1/2 turn
3) Screw in heatbreak into the heater block until touching the nozzle
4) Heat up heater block + nozzle, grab heater block with pliers and screw in nozzle as hard as possible with a hex wrench

Is this fine now?
The nozzle has a little gap to the heater block, but I guess that's fine as in theory it's sitting firmly against the heatbreak now, right?

That sounds good, exactly how i do mine and no leaks.