descale a motor

I have a new project and I want to descale the motor before I install a new radiator but I don't want to remove the motor .... any ideas ?

Get a couple of those flushing kits and use'em with the old radiator still in it. Then flush / flush / flush until clear.

If your talking about the cooling system---you can also just use a barrel of water, pump into and out of it either filtering throw a old cloth blanket or just letting the scale go and settle to the bottom ob barrel