Has anyone dealt with a rattle in engine compartment during first start up of the day, but as soon as you give a little throttle goes anyway until next cold start up? I have checked everything I can think of and taken it to dealer and have been unsuccessful.

 

Serpentine belt tensioner or idler pulley??

 

Did not think of that!! Is there a way to tell which it is w/o just replacing it.

 

id start,let it idle,see how long it rattles? look , listen while it rattles,spray water on rotating stuff. see if it changes. push , pull stuff.
you gotta think like a noisy motor.

!!

 

It would be helpful if you would provide, year, model and motor info if you want an accurate answer.

Next time you are going to fire it up for the first time, open the hood first and have someone else start the motor so you can hear where it is coming from.

If you have an I5, I'm confident I already know what you are hearing, but I'll wait for more info from you.

 

Sorry it is a 2008 Hummer H3 3.7 liter I5, Adventure package, KN cold air intake, jet chip stage 1.... Thanks

 

I have had that occur this week and it's driving me nuts. It sounds like it's rattling in the right hand airbox or behind the glove box. Maybe yours is rattling in a different area. This particular noise isn't the exhaust manifold either, it sounds deeper than that. This has me quite stumped. If I find anything I will let you know.

 

That sounds like the same area as mine!!! I will let you know what it is when I find it.

 

Doc, what do you think it is?

Sometimes, I too, hear an almost indiscernible noise from the front end of my rig.

 

The OP may not have given the best description but he is relatively new and may not realize that sometimes other info is needed. No reason to be sarcastic when someone is learning.

There have been countless issues solved here with little info given.

Doc you said if it's an I5 you know what it is pleasse don't keep us in suspense

It's not one of the common issues we have heard here. I can't hear it when I am outside the truck with the hood open. Not the heater hose going through the firewall.

The next 2 items I will check are the small lines that run across the top of the firewall - I can wiggle them by hand and it could be the little plastic clips rattling against the firewall
OR
The wire for the antenna hitting the inside of the fender.

Yesterday I didn't hear it at all