ML350 G6 fan replacement

[espen4001]

Hi! I have a ML350 G6, and I'm working on replacing the stock fans with something more silent, and so far I have bought Noctua PWM, and modifeid the 4-pin connector to fit the 5-pin HP connector. This is working, as far as system reading fan speed and status. ILO reports all OK, and runs fine if I replace only the 3rd system fan, and leaves fan 1 and 2 with stock. When I replace the fan near the cpu heatsink, ILO still reports all OK, and all temperatures are fine, even maybe lower than before. The weird thing is that the fans starts running at 10% at boot, and slowly increases, 1% at a time. It has been running for 50 minutes now, and has reached 70%. Does anyone know why it increases the speed, even if temperatures are OK? The noctua fan has lower rpm than stock, so rpm is lower than what the system expects, but does this affect the fan speed output from system? I would think that temperatures would be the input to the fan controller, but obviously also the rpm feedback is used as well. Will the system shut down when it reaches 100%? Can the feedback be manipulated someway, so the system thinks the fan is running as expected? If it will reach 100%, and not shut down, I will try to swap the last fan as well, and maybe the new fans at 100% won't be as noisy as the stock fans at 30%.
I have latest ILO version, 2.29, and bios version D22 3.1.2010.