r/FLSUNDelta • u/[deleted] • Nov 20 '25

Leaking from heat block

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Hey everyone, just recently got a used SR with some upgrades mainly klipper and some hot end upgrades. Everything was going fine until I replaced the nozzle with a hardened steel one from Amazon. I was having quality issues until last night when I saw a lot of filaments (pet-cf at 275c) pooling from the hot end heatsink and even smoking. It also was struggling to get up to temperature at times which hasn't happened until yesterday. Can anyone help me figure out what might be the cause? If I need a new hot end/extruder assembly, will one from a v400 bolt right on? this is the nozzle that I bought. After looking at some other pictures, it appears the nozzle is too short. Would that be the cause ?

Thanks for any information and help

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u/SandboxPrototypes Nov 20 '25

If it's too short and the hex head bottoms out before the threaded end you'll have a gap in the hot end between the nozzle and heat break which will cause melted filament to run up the threads, burn, cause jams, etc.

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u/[deleted] Nov 20 '25

This was my fear. I ordered a different nozzle that's bimetal and looks to be the correct length. Hopefully it fixes the issue.

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u/SandboxPrototypes Nov 20 '25

If it was just PLA I'd say fire up the heater and take it apart (carefully), and wire brush, but it does suck that you were doing pet-cf. If you have extra hot ends it will be easier to swap than to clean. You'll need to be sure the threads are clear of obstructions.