Hammerdrop

I'm getting older and thinking forward to a day when I might look to pay for a coolant flush so I watched a few YouTube videos using coolant flushing machines.
It seems that this procedure is done by applying a vacuum to the radiator cap opening and just sucking out the coolant. One video even said that the procedure is finished when the radiator hoses collapse ! I don't see how this can work very well, and there is no concern about collapsing the a flimsy heater core or reserve tank. Another video said the engine is kept running during this process ! What ?! How can this method possibly remove sediment from the radiator or anyplace else? I would think that a wet vacuum along with one or two strategically disconnected hoses would work much better, especially with modern vehicles that don't have any block drains on the engine.
What am I missing here ?

Koda

You're missing that it's horseshit. Don't do it.

bccan

Most modern vehicles, after draining, like to be filled via a vacuum setup to decrease any chance of air in the system, it’s very effective. Without it, shop/tech is playing “cooling issue roulette.” In our old cars, I don’t see any need or advantage to it, I certainly don’t see it removing any sediment.

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Olds64

I don't about vacuum flushing the radiator, but for our classic cars the easiest way to flush the radiator is with a garden hose and coolant flush kit. Per the manufacturer's directions the petcock should be open with the motor running and the garden hose ON for the flush stage.

https://prestone.com/product/prestone-flush-n-fill-kit/