Whine under the hood- First Thing AM Only

[Nottajeep]

Anyone know what this sound might be? Fan, pulley??

It only happens first thing in the AM after the LC sits overnight.
Throughout the day, it is quite on startup...

It's only after overnight w/o engine starts... the rest of the day the sound is gone??
2012 07 11 07 24 34 223 - YouTube
2012 07 11 07 25 33 8501 - YouTube

 

[lcmariani]

When was the last time your timing belt was changed?

 

[Nottajeep]

TB= 35K ago
Serpentine = 20K ago

 

[lcmariani]

How many miles are on your truck? It sounds like a bearing... It could be one from the idlers. Did you change the idlers when you did the timing belt? It could be anything else that has a bearing that the serpentine belt turns.

 

[Nottajeep]

Idlers were left untouched on the first TB I believe, but can't confirm since I was not the owner at the time. Weird thing is the sounds goes away shortly after warm up and doesn't return until the following AM.

Other thoughts are master cylinder or some type of fan???

 

[re_guderian]

My alternator made a noise for a long time before it finally died.

 

[1loudLX]

I had cold start bearing noises. Then my tensioner pulley on my serp belt seized and ruined a nice day of wheeling down in the San Juan's.

 

[Nottajeep]

I had cold start bearing noises. Then my tensioner pulley on my serp belt seized and ruined a nice day of wheeling down in the San Juan's.

A pulley on Serp belt sounds a lot better than going back to the TB job...

 

[re_guderian]

Serp belt pulleys, including PS, alternator, tensioner, etc. seen much more likely to fail than idler pulleys and TB components, just based on historic failures around here...

 

[APKhaos]

On a cold morning startup, mine used to sound like a bad garage band.
Did the serp belt and replaced the pulleys as part of the timing belt job. Silky silence, so now you can really hear the cat heat shields rattling. Welded them once, and have the stainless band clamps on them too. Teh clamps seem to loosen over time for some reason.....

If you have a stethoscope, its easy to find the source. If not, just use a length of clear vinyl tubing - one end in the ear and poke the other around until you find the source/s of noise. Please be careful with the fan while you are poking & listening.