The only 'hardened residue' I find is cat food ... our 2 'boo's' leave behind. One is a picky little be-atch, showed up at the door one night ...the...
Yea, everything - vac. chuck, draw bar, pump, gauge and everything to put it on and use it. I like having the Gauge so I can see if it starts leaking...
Hmm...it just occurred to me that the last time I saw a K&S display, it was picked clean. But that was during the supply-chain issues 2-3 years ago....