H115i running hot

Hi all. I have an H115i on an asus prime-a (with i7 8700k) experiencing high idle temps (46 degrees). In cinebench R15 it gets to 98 degrees. Overclocking is XMP1, 48, 1.3 vcore. Nothing that should cause these temps.

I've cleaned the fans and rad, but not yet cleaned and reapplied thermal.

I'm connected to CPU_FAN though I'm now questioning this as someone else told me that on this board I should be connected to W_PUMP.

RPM on the fans hovers around 1500 and the rad doesn't seem to heat up much. I'm suspecting faulty pump (purchased Oct 2017) but would like some guidance / input.

What is the H115i Temp (coolant temperature) in iCUE? Typically you would run about 4-7C above room temp at warm idle and see loads temps +4-8C on top of that, depending on type. However, if you are seeing idle coolant temps in the 40s, it increases very quickly under load, and then takes an eternity to cool back down, you are probably looking at some type of flow restriction in the cooler. Other physical signs to look out for are one warm, one cool tubes or if the exhaust from the radiator feels cool but the liquid temp is high.

The motherboard fan header connection is irrelevant. That sends a RPM to MB and nothing more. The power comes from the SATA connector and info is passed via USB. Most people should leave it on CPU fan so you get the CPU boot error if the pump doesn't start. If you do move it off there, you will need to disable the CPU fan detection system in the BIOS.

What is the H115i Temp (coolant temperature) in iCUE? Typically you would run about 4-7C above room temp at warm idle and see loads temps +4-8C on top of that, depending on type. However, if you are seeing idle coolant temps in the 40s, it increases very quickly under load, and then takes an eternity to cool back down, you are probably looking at some type of flow restriction in the cooler. Other physical signs to look out for are one warm, one cool tubes or if the exhaust from the radiator feels cool but the liquid temp is high.

 

The motherboard fan header connection is irrelevant. That sends a RPM to MB and nothing more. The power comes from the SATA connector and info is passed via USB. Most people should leave it on CPU fan so you get the CPU boot error if the pump doesn't start. If you do move it off there, you will need to disable the CPU fan detection system in the BIOS.

Thanks for the reply. Yes, temp does take a long time to come down - typical 1 degree every 5 seconds. It was purchased in late 2017 so I've raised an RMA. Hopefully they'll get back to me fairly quickly as I'm reluctant to game on it at present.

A 1 degree drop every 5 seconds would be fairly rapid (after load stops). If you have a flow issue, you might hit 50C on the H115i Temp and it stays at 50C for 30-60 minutes after you stop. However, this can also happen if the case environment is extremely warm. That's why it's important to check for other symptoms like cold exhaust or clearly different temp feel tubes.

The case has 4 intake fans (120mm) and 1 exhaust (120mm). The motherboard temp is reading 27. So I don't think environment is the issue. The corsair usb fan came in the post so I've put that on and got iCUE running now. This has recorded the pump temp at 45.5 degrees. After cincebench test it goes up to close to 50 with the CPU temp apparently at 99.

The screenshot here is 2 mins after cinebench ended.

I don't like the 45C idle coolant temperature. That is beyond max load for most people. The CPU to coolant differential is also too high. Normally that is attributed to contact issues, but it is also possible when the flow rate becomes too low and the coolant stays in the CPU block for too long. I would say there is some type of flow problem.

Support is likely to probe as to whether the environment or other factors are influencing the temperature. Make sure you stress to them this is new behavior and take off any dust filters you have on the radiator panel so that does not become a question later. There are lots of reasons you can hit 98C on the CPU and many of them are not related to the cooler. The 45C idle H115i temp is the strongest piece of evidence you have this is cooler related.