Well there's two things here
I just stripped the top card down, the one that is getting the hottest, and one of the stand offs closest to the gpu just fell off. The thread was completely shot, and half of it was still in the block. I remember when I first installed the blocks, that it was a real you know what of a job, and perhaps one of the holes wasn't machined right. I don't know. Anyhow, I've contact EK for an RMA. I reckon the block was faulty, and wasn't making contact on the GPU
The other thing is the pump. When I increase it to no.5, there is no difference in sound at all. It doesn't get any louder at all. It's almost like the screw at the back isn't attached to anything, and not doing anything.
So first job, is to RMA the block. I can't send it back to the re seller because it was a backstreet small guy and he only had two in stock. The bottom card's fine, doesn't get hot really, just the top card.
After that, I'm gonna drain the loop, get rid of all the air locks in the rad from continually re connecting and disconnecting from gpus to fault find.
Then after that, if that doesn't work, will have to RMA the pump too.
Jeez. What a nightmare.