sometimes an alt electrical malfunction of a certain type (diode?) can make a squeal usually high pitched like a siren which certainly ain't the case here but it would take 3 seconds to pull it to elim that & swapping the alt would be easier than swapping a pump but the alt would do it at the parts house the same way (be making the noise) so but now the pump is looking guilty tho I would think the noise would increase with RPM