my neighbor had a similar issue on his Benz, he disconnected my large cooling fan plug (ie the auxiliary fan assembly ) behind the radiator, i.e., the big fan.
and the noise stopped ,
yet the AC & Heater fan I assume it still works since it was pushing air though the inside vents.
you sure its not the auxiliary fan assemblies bearings are are shot?
that part at "parts geek .com" is $600.00
why then when the heater is off the sound is very quite, yet when I put the heater fan to high it is a very loud noise. Its cold out , so I have no real information when the ac fan is turned on.
I'll go out now , & hit the fan on to see if it is the fan motor.
does the cooling fan speed up when one turns on the heater to high fan??
are you sure it is the cooling fan motor? i.e., the "auxiliary fan assembly"
the noise comes from under the hood, at the cooling fan /auxiliary fan assembly . same item different name right?
One is for the main engine cooling (cooling fan) the other is for when a/c compressor is ,A/C on or defroster is on (auxiliary fan assembly)
i'm ready to accept but the same original question is there, i cant be certain what you have todl me.
is the big cooling fan multi speed or are you saying there is a 2nd fan for thre ac heater defroster???
there is no fan noise when the big cooling fan is unpluged, but when pluged in it makes a fan noise then when I turn the ac/heater/defroster on , and turn the fan sped all the way up---
the large cooling fan i.e., the auxiliary fan assembly fan makes a loud fast whooooo noise.