Cleaning radiator and CPU block

[murah]

Hi all I have some second hand watercooling parts from the MM and they could use a clean before I pop it in my rig what's the best way of doing that?

I have some Ispropanol 99% alcohol would that be safe or might it react with any seals?

 

[murah]

the CPU block looks clean really but I might run hot water through it, the rad on the other hand has some gunk from the previous owner's loop and I have about 20gallons of ISO so figured it would do the job, can't see an issue with it on the rad myself but just in case