Basically right, where I worked the parts were set in trays to air-dry overnight. There was a spot on the tray for each part, o-ring, and gasket so you could easily see if any were missing.
The machines were reassembled the next morning. So the closers only had to break them down, wash, and sanitize.
Once a week any dairy mix left in the machine was discarded, this "breaks the cycle" of any bacteria in the mix. So on that night, you tried to let the machines run very low to minimize waste.
It's sort of complicated the first few times but it becomes very routine. Like everything at McDonalds, there is a detailed step-by-step written procedure on how to do it.
Yeah, I was thinking more about the grandparent above that said it took 45 minutes and that had to mean breakdown/cleaning/reassembly in one step. I was there in 1985-86 and we did like you said, one crew member did the cleaning at close and let it air dry for the morning crew. But that was also because shakes/ice cream wasn't served during the breakfast shift. Someone had time in the morning to assemble and prime the machine before 10:30am (me).
I'm guessing 24/7 operation changed when and how the cleaning was done, leading to more contamination instead of less.
The machines were reassembled the next morning. So the closers only had to break them down, wash, and sanitize.
Once a week any dairy mix left in the machine was discarded, this "breaks the cycle" of any bacteria in the mix. So on that night, you tried to let the machines run very low to minimize waste.
It's sort of complicated the first few times but it becomes very routine. Like everything at McDonalds, there is a detailed step-by-step written procedure on how to do it.