I just bought a 1997 F150 4X4 off road ext. cab 4.6 V8. I can hear a slight rattle and it sounds like it's coming from the altenator. I can't really pinpoint it, but I put my ear as close as I could to it and it sounds like where it's coming from. Any ideas or tests to see if it is the altenator? Thanks!

 

Sounds like the bearings in the alternator, you may be replacing it soon.

 

Lots of items on the front of an engine can make rattleing sounds so you have to go about checking for it systematically. Some recommendations:

If you don't have a belt diagram as to how the component drive belt is routed, draw yourself one and take off the drive belt. Then with the engine not running and the keys in your pocket go to each individual component and try turning it by hand to see if you can locate/duplicate the rattle/noise. If it is the idler pulley sometimes a good shot of lubricant will fix it for awhile but eventually you will probably have to replace it. You can also try starting up a cold/cool engine, while the belt is removed, FOR A VERY SHORT PERIOD OF TIME SAY NO MORE THAN A MINUTE OR SO, to check and see if the rattle you're hearing is coming from the engine or not. If it does prove to be the alternator bearings or one of the other drive components( AC,waterpump,etc.)you will have a more significant problem to fix and you should refer to the appropriate tech manuals for help.

 

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Thanks for your reply. I will definately try that!