1998 F150 4.2

Just started making this noise. Very prominent at idle, will change/go away at certain RPM's


http://www.youtube.com/watch?v=lz1cw...ature=youtu.be

 

Sound like an idler pulley or alternator bearing, possibly even water pump . To narrow down use an automotive stethoscope (cheap is fine, try Harbor Freight) If not available you can check with a long screwdriver( I mean 3 feet or so, you for sure you dont want your hair near moving parts). Put the handle of the screwdriver in your ear and touch each component while the engine is running. The sound will be conducted along the screwdriver. As loud as yours is it should be easy to find. Touch the idler on its center bolt.

 

Thanks for the reply.

I did check the alternator with the screwdriver method and it sounded normal. I will check the idler next.

Now that you mention it last time I replaced the belt the tensioner was really weak. don't think I can get at it with a screwdriver though.

 

You can remove the belt and spin each pulley by hand, see if it feels rough or makes noise.

 

Does it do it with the belt off? If it still does check the pvc valve, they can make strange noises sometimes. Kind of sounds like a whistle in a way.