'99 EX Sport....again. Engine noise with lights on?

[GAGrl78]

So, as of last night, there is a grinding noise coming from the engine compartment when the truck is in park or neutral but ONLY when the headlights are on. I thought it might have been the alternator, at first but it's good. The noise seems to be coming from the drivers side, above/beside the wheel. When the noise starts, the idle lowers a bit as well. Any ideas at all? I am completely lost on this one. :scratch:

 

[SoNic67]

When lights are on, the load on alternator increases, and so does the tension in the belt.
Any component that is driven by that belt will see slightly increased pressure on their bearings and, if those are worn, will start to make noise...

Use a long screwdriver to listen to different components.

 

[GAGrl78]

That makes perfect sense but wouldn't that cause the noise in any gear, rather than only when it's in park or neutral?

 

[J_C]

When the noise starts, does it persist continuously for a while or just end right away then repeat later?

If you hadn't written grinding I would have suggested cleaning out the IAC valve, but if you haven't cleaned or replaced it in the last few thousands of miles it might be worth trying.

 

[GAGrl78]

It's a constant noise. I did clean the IAC valve in December. It sounds just like turning the key with the truck running. No one I know has any idea what it could be so any and all ideas are very welcome. It seems to be coming from near the firewall, at the bottom, on the drivers side as far as I can tell.

 

[swshawaii]

Don't be alarmed by the linked title, but 2000StreetRod's instructions are by far the best way to detect engine noises. "Grinding"
only happening with the headlights on in park or neutral is baffling, at least to me. Please be careful around the running engine.

Timing chain rattle resolution process - SOHC V6
http://www.explorerforum.com/forums/showthread.php?t=278100

 

[JusTheUsual]

Could be your starter.