You really need to have a look at those temperatures because 80C is way over what a i5 can take. The CPU you got have a max of 72 degrees. What it sounds like is that you might not have gotten the cooler onto the chip snuggly enough so might be an idea to check again that the cooler is correctly seated on the CPU, the heat transfer will fail otherwise.
Here's a link for a Intel diagnostic software that will tell you if the temp is ok or not
https://downloadcenter.intel.com/Det...&DwnldID=19792