I pulled my engine cooling fan out yesterday which only took 10 minutes. I applied 12 volts to start the fan motor several times to see if it would make this growl I have been hearing coming from my engine bay. The motor ran just fine at high speed, and by starting the motor several times it would not make any unusual noise.....The fan motor seems OK. I would have bet the fan motor was the culprit since it comes on now and then when driving. I replaced my drive belt last year at 30K, and all the rollers were OK. After recently checking they are still OK. Not sure where this weird noise is coming from.
