Y’all were right, the heat break and the nozzle weren’t tightly connected. I’ve burned out the nozzle, the head break, and I’ve extricated the thermistor for later reattachment…the problem is: I’ve lost the wrench for the grub screw…how do I clean all this greasy stuff off the heat block so that I stand a chance of getting the thermistor to stay put? (pssst. @Sanjay_Mortimer , any hints?)
Molten PLA can take that out, or acetone.
Acetone if it is ABS - MEK substitute if PLA - and a good soak. The grub screw wrench should be just a standard hex wrench available in a hardware store
@Mike_Miller Get it hot, 190C should do, use a toothbrush for the exterior. Then let cool and add solvent for the appropriate plastic residue as per @Doug_Rector says. So far I have found Dichloromethane much more effective than MEK as a PLA solvent.
Thread an M6 bolt in and out repeatedly to clean the interior. If you happen to be a rifle shooter you may have some bore brushes, which are ideal for cleaning inside M6 threads. Anything from .22lr to .270 (7mm) calibre works great.
I’ve had hotends in much worse states, and just assembling them back together while hot works just fine. Despite the filth. No cleaning needed.
If you really do have a good effort at it and it still doesn’t work properly then get in touch, we’ll sort you out, even if that may mean free replacement components.
Also, I don’t think it’s likely you’ve killed your nozzle and break, so no need to buy a new one. The cleaning strategies above should work with those parts.
Thanks guys, I’ll pick up some MEK (unless y’all know a brand name for DiChloroMethane) and demote my toothbrush for the cause.
Anybody know, offhand, the size of the hex wrench? It’s smaller than anything I’ve currently got.
I just wanted to make sure the surface was clean enough to hold the Kapton tape (now it’d just get hot and slimy and the tape would fail.)
I appreciate the offer on the parts, @Sanjay_Mortimer , I’m doing what I can to make that unnecessary. 
I was able to remove, and cook the nozzle and heat break with a MAPP torch, but couldn’t remove the cartridge heater to cook the rest.
(and thanks, Y’all are the BEST!)
1.6mm hex for the grub screw on mine. You’ll find them with precision sets. If you are in the US, good luck finding one! I’d suggest Amazon or a local hardware store as home depot / Lowes will likely not have them. You can try tho!
I have plenty of those wrenches and can send one - get in touch through the Filastruder contact form.
don’t sweat it, Tim, there’s gotta be one closer to me…there’s a Microcenter just up the street.
according to a chart I found 1.6mm = 1/16" which should be easy to find in the US.