(Redirected) Lound fan noise and strange smell _15R SE 7520 Dell Inspiron

Hello everybody, 

I have a problem with a fan of my 15R SE 7520 Dell Inspiron. Generally a fan is a bit loud. But sometimes it becomes very loud and then quieter again. It is very irritating as you can imagine. But, in addition to that, sometimes I notice a smell something like plastic out of fan. I went to PC Repair and they cleaned a fan as well as CPU Heatsink and exchanged CPU Thermopaste. It did not last long and it is as before again.

Should I exchange the whole fan and CPU Heatsink unit or is something different is broken in my laptop. 

Hope anyone can help me.