h100i Platinum high temps in 280x

Hello all, first post here, figured I would ask here first before contacting Corsair proper.

I just recently built a new PC and the thermals have me wondering if something is wrong with the AIO.

I built the PC in the 280x with an h100i Platinum cooling an i5 9600k (no OC). idle is low 40s/high 30s, under load is averaging mid 60s to 70s. My previous computer was a 6600k (OC'd at 4.5ghz) with an h80i in a Carbide 500r. Idle temps were low 30s, full load was average mid 60s to 70s. Are mATX cases usually that much hotter at idle/low load?

The h100i water temp starts around 32c at a cold start and then under load just saturates to around 40-45c and then takes a really long time to come down and comes to a steady 35-36c at idle. I've even tested with some Omega T/C's placed in the radiator core and it doesn't seem like its rejecting heat very well. The water temps would be 40ish and the air temp in the radiator core was 5c(+/-2) above ambient.

Coolant lines are cool to the touch.

Is this unit malfunctioning?

I know that the temps are a little hot at idle and fine under load, but the fans...dear god the fans...that little 280x sounds like its going to take off and fly around my room once it saturates and then they never spin down.

What I've tried:

- Reseated cold plate and applied Kryonaut TIM...twice. Made sure thumbscrews were tight both times.(no change)

- Changed fans from push to pull, then back again (pull was better)

- Changed pump from CPU header to AIO header on mobo and fans from pump control to CPU and CPU secondary headers (no change)

- Removed 280x top dust filter (no change)

- Changed fan curves around from each type and back again, and around and around...manual, extreme, quiet...etc. (no real change, even on extreme)

The only thing that sort of helps is pulling all of the glass off of the case.

I'm thinking that there is something wrong with the pump because of how the rad really doesn't get hot at all. Thoughts?

Any help would be appreciated!

Thanks guys and gals!

I think you will find those coolant temps are following along with your case temperature. Local case ambient is always going to be minimum coolant temperature. Either way, that is the data you need to assess first. Even after the load ceases, the cooler is slow to come down because the case temp has increased during the load phase.

As for the fans, no more presets. Make your own custom curve. There is no external temp sensor or microphone to make the fan curve more true to its name. It is a set of preprogrammed data points like any other. Set your curve to reasonable fan speeds for the coolant temp range you operate in.

My PC is in a 280x as well with the H100i RGB Platinum and an i7 8700K (no OC). My CPU is 30C at idle and into the 50s under load. My rad is 26C at idle and usually stays in the mid-30s under load. Mine is in a Push & Pull setup and front mounted on the 280x. I also have upper fans to exhaust and an additional lower fan for intake below my RTX 2080ti. The 280x can get toasty, depending on the GPU, so getting that hot air out is pretty key. My ambient room temp is around 21.5C.

I use LL fans with the ML from the AIO and find it's pretty quiet, after manually creating fan curves in iCUE.