Just got a Inspiron 5675 and with AMD 1800x cpu. However, it seems the fan is not good enough to cool the CPU to realize its full potential.
So, I want to add a liquid cooler by myself. But will this void my warranty?
If it's done in such a way that you can reverse the process transparently should repair be needed, no. If you end up altering the chassis to fit the fan, and Dell sees this -- they could well deny warranty coverage. And of course, were the setup to leak and short out the system, that would be easy to detect and result in a denial of warranty coverage.
Warranty Voiding will happen when the cooler leaks corrosive material onto the motherboards and other exposed parts. Coolant leaks are like hard drive death. Its not a matter of IF its a matter of WHEN it happens.