04 taurus was making a rumbling noise And sounded like it was the bearings inside the alternator so I changed it and that was not the problem. Does anybody have an idea?
Belt tensioner a thought, a stethoscope can be helpful.
Take the belt off one of its pulleys. Then rotate each pulley it rides on, feeling for roughness or play.
Belt tensioner likely. Loosen belt enough so there is absolutely no pressure on any pulleys. Then feel if there is play or slop in any of the pulleys. Also if your battery becomes discharged, the alternator can make a pretty noticable whine while producing lots of currant. Stethoscope is best though.
good ideas above, that’s where to start. water pumps can make a noise like that. listen through a length of old garden hose as a way to isolate where it is coming from. as mentioned above an electrical system problem can load down the alternator, and that would do the same for a new alternator. seems unlikely, but one quick way to check for that is to note if there is a big change to the sound when turning on electrical equipment, like the headlights on bright, electric window defrosters, etc. Make sure the engine oil level is ok, as the valve train and timing chain can make rumbling noises if oil-starved.
It’s usually possible to run the engine briefly with the drive belt completely removed as a test. That’s a way to tell if it on the drive belt path or not. caution: the water pump may be on the drive belt, so only do that briefly, when the engine is cold.