If the fan is loud there are only a few things that will cause this. 1. the fan may be backwards on the cooler. 2. the fan bearings are worn out. 3. the fan RPM's are really high.
For #1. the fan should be attached to the front of the cooler pushing air through the cooler towards the rear of the case.
For #2. If the fan bearings are worn out then the only cure is a replacement fan. If the fan blades rock excessively from side to side then the bearings are bad.
For #3. if the RPM's are high either either the motherboard is not controlling the RPM's properly or the CPU is overheating.