When I first bought my truck (used) the alternator made noise and I put some WD40 on it and it stopped for a day and started again. Now I'm not a dumb *** (excluding spelling)and know that WD40 is for cleaning and not lubrcating and put some machine oil on it the next day same result. Is there anything I can do to stop it or I'm i'm just going to have to buy a new one. It's got 67,000 on it and that seams like it time to for a new one any how but why spend $200 if you don't have to yet.

 

I also have a slight squeak in mine at startup then it goes away when warmed. Try some silcone spray and get the tube adapter inside the rear of the alt. and spray liberaly and often.

 

Are you quite sure it's the alternator? I have to replace my serpentine belt about every 20,000 mi. Otherwise, I get a squeal in the morning when its cool out, like now.

 

Just a FYI. I bought my 98 150 new and my alternator always squealed I had been changing the serpintine belt on a regular basis and one day (98,000 miles) my battery warning light came on. Yep the alternator went on me. I knew it the second it happened. I had a creative way of driving almost home but my suggestion is if your alternator is still working buy a new one and leave it in the truck because when it goes it goes fast. And always change the serpintine belt on a regular basis, part of PM.