another weird sound

[darocc]

i keep hearing this "suction" sound which lasts roughly 2-3 seconds coming from the engine, only when the heater is on ( starting to get cold here in montreal) it happens whenever, while driving, or just idling
is this just from the heating system? or something from the engien itself, anyone have this sound too?
the sounds really dont bother me about this car, just if its something thats not right and that could affect the engines durability, i want it fixed

 

[changedman]

its the fan coming on

 

[darocc]

no no, this is no fan noise ,this is sucking slash grinding sound, hard to describe really