Z490 Build

If you remove the liquid head off the CPU it breaks the TIM compound seal and it will require complete cleaning of the CPU and liquid head, then application of a decent thermal 'paste' which is different.

I found the TIM pad that came with the H150i to be good. I did not have any reason to replace or change it.

If you want to try replacing the TIM with a paste (or something like liquid metal CoolLabratory Pro), you can, but just remember once a TIM pad seal has been broken by removing the liquid head, you can not put it back on without cleaning the TIM off both parts and replacing it with paste or compound. 

Pulling it off and putting it back on with the same TIM is a no-no.

I have never heard of a tower with all fans blowing out..   that seems strange. Typically there is some type of pass through air flow that brings cool air from outside the tower, inside, and then expels heat from inside the tower, out.

Which way and which direction can sometimes be a matter of trial and error. And if a tower is jammed under a desk it can succumb to recirculating its own heat as the heat is trapped und the desk or in a cubby. Tower needs to be able to breath. 

In with the good air, out with the bad 

Folks have said my suggestion for towers in the past are monster boxes. Smaller or more compact towers can't breathe the same volume of air a good size full tower can and although the larger towers may appear to be somewhat obtrusive, with the fans and air volume they provide, they can sometimes make a positive difference to the end result

First of all, I never got to 5.1 and was hitting the wall with 5.0. The possible reason? I really wanted to reuse a Lian-Li super case from an old build but with the one disadvantage that it only had room for 2 x 140mm fans at the top so I had to use the Corsair H110i cooler (280mm). In percentage area terms not such a big difference but it was key in my not hitting 5.1 I think! Basically that cooler can handle around  220-230w processor load, not enough for 5.1 or higher with the 10900K. 

Originally Nick asked if I was interested in trying the build on air just to see where I could get. Unfortunately I didn't have the time back then but I suspect the results might have been similar.

That said, in actual use with all my current sims (including MSFS) it's more than enough. In fact I have three tested profiles, 5.0, 4.9 and 4.5. Even at 4.5 it cruises along nicely at even lower voltage, power and temps and I find I'm using that profile most of the time currently.

After experimenting I found having my rad at the top, exhausting air pulled in from the front plus a rear exhaust fan, was best at cooling the rad and getting rid of heat from the GPU which I hadn't fully considered at first. I also use high performance fans and the ones on the rad are pressure rated to force the air through. It's a bit noisy at full throttle (only needed during clock testing) but in normal use not a problem at all.

I appreciate there may be a more than linear jump in performance going to 5.1 or higher and that's an option to try with a new case if I ever feel the need.

Rob