The fan on the cooling system makes a horrible noise!
What kind of noise? Likely something fell into the vents and is now hitting the fan
Nothing in the vent. Not a hose. Had that checked.
Are you talking about the radiator fan in the engine compartment? If so, check to see if the blades are hitting something as they turn, like might be caused if the fan motor came loose from its moorings. Or could be the fan motor bearings are worn out, which would require the fan motor be replaced. The part won’t be overly expensive, but there may be a significant labor fee. Good idea to not defer the diagnosis b/c something more expensive than the fan & fan motor may get damaged in the meantime.
There’s something inside the chamber where the heater fan runs. It can be leaves, or it can be acorns like in another thread, or who knows what. Mostly they come in in the little paws of our fellow animals, the rodents.