Sounds like a pump... comes on randomly or so it seems
Basically that'* it. The key isn't in the car, nothing is turned on, it'* not the antenna motor and it'* not the blower motor (that'* disconnected because it won't turn off). It'* an electric pump-like whirring sound, almost like a fuel pump but it comes from under the hood. When I replaced the battery it came on immediately after I hooked up the new battery and ran for about 10-20 seconds or so. Then later, while I was draining and re-filling the radiator, it came on again for about 20 seconds, stopped, then came on again--and again it was for a very short period of time. Very strange. Any ideas?