Little flow mk3  

Re: Little flow mk3

It's hard to be certain, but your new nozzle may be touching the bed.

Turn the live-z way up (closer to 0 than -.xxx). Restart the tuning. And look for the "Life Adjust My Way" thread to get a much better method for adjusting your offset.

Re: Little flow mk3

Also, did you increase your hot end temperature slightly? Steel has poorer heat conductivity and will need a slightly elevated temperature to print at the same flow rate; if you're already at the lower end of the temperature range for your filament with brass, this would result in no flow or a lot of clogs with steel.

Re: Little flow mk3

I agree with Peter, it looks like you're way too close to the bed. The thin extrusion is one clue, but that tell-tale clunking noise is your extruder skipping as it tries to physically shove the filament through your print bed. I had identical symptoms when I tried a cheap $15 "flex steel" bed from AliExpress, and had to back my Live-Z way off. I wound up going 0.45 higher (less negative).

The problem is that a new nozzle from E3D should not require a different Live-Z setting. They are precision made to have identical lengths. Double-check your nozzle installation before "fixing" it with Live-Z adjustments. Be sure you've got the new nozzle properly tightened. If not, it will be lower than the previous 0.40mm nozzle which could account for your problems. Did you heat the nozzle up (265-280C) while installing the new nozzle? You want the hotend hot for maximum expansion during installation. If you don't, you could wind up with a really nasty filament leakage around the nozzle and possibly up inside the hotend which will ruin your evening.

If you're certain the nozzle is properly mounted, I'd suggest backing your Live Z off at least that far and working it down slowly. Better be high and waste filament than damage your PEI sheet. As Peter suggests, the "Life Adjust" procedure is much easier to use for Live-Z calibration.