Sounds like you have a problem.
100c. will cause throttling.
What is the make/model of your new case and fan arrangement?
What is your cpu temperature at idle?
I would expect 10-15c. over ambient if the cooler is functioning and is mounted well.
Much higher than that can be caused by a few things.
- The pump is not mounted securely and level.
- The H100I has some air that has entered the system through permeation of the cooling lines.
- The pump is failing.
- Particles have entered the system.
In time all aio coolers will have this problem; they do not last forever.
I7-6700 is not overclockable so it will not generate much heat.
If you need to replace the cooler a simple tower type cooler with a 120mm fan will do the job.
If you still have the original stock cooler, it will be noisy, but will do the job.