We need more details. What are the specs of your PC? What cooler does it use, if you know? How many fans does it have, and where are they placed? Can you post a picture of the inside of your PC if possible, so that we can determine the case, cooler and fans used? And finally, could you leave a link to where you bought it?
Watercooling is a major step, and if the CPU cooler is not at fault will probably not sort the problem. AiO water coolers, which is what you would buy, since a full custom watercooling loop is probably too expensive and complicated to set up, are still less reliable than comparable air coolers which are just as quiet, and don't make the CPU run any cooler too.