Would it be possible to extend a closed water cooling system like a corsair H100i and just buying an extra radiator and more fittings and tubing so you can cool your GPU with just the built in pump and reservoir of the closed system?
And how would you go about doing this if it is possible?
Sorry if there is already an article about this, I must have missed it, please link me if there is.
It is possible, and has been done before. But the people who did, weren't that happy with the performance afterward.
The pump on CLC water-coolers is quite weak, barely capable of powering what it comes with at stock. Adding in a GPU block and radiator would be too much restriction.
Also, CLC coolers often use Aluminium rads, which is a metal that is known to cause Galvanic Corrosion when the typical water-cooling metals (Nickel, Copper, Brass) are present. You could end up corroding your GPU block unless you take precautions.
My advice, just go full out with a custom loop. Get something like a Raystorm D5 kit, then add in your rad and GPU block.