Lets play...What's, That, Noise?!?!

I have a 2012 Tacoma 4x4 V6 with 155,000 miles on her, and recently I have begun hearing this inconsistent rattling noise under the hood that i can't figure out what it is. It's not consistent and only last for 3-10 seconds when I first start up & moving or later if I am idling. Once underway for a minute it goes away. I spayed some belt quieter spray in foolish attempt, but it did nothing Any ideas? Sounds like a piece of metal vibrating/flapping/rattling.

 

May be the fan clutch?

 

intake pipe through the fender well?

 

Heat shields?

 

Definitely something that gets quiet as it warms up.
Exhaust manifold shield?
Intake? 2ndary air pump?
So many possibilities.

 

Mine rattles. I take and spin the hose clockwise on the filter housing before I tighten that clamp

Edit: I've found my heat shields rattling where they bolt on. A couple of fender washers sandwiching the metal took care of that.

 

I had the same problem, washer fluid container came loose after taking it off for a retrofit. Maybe yours came loose too? Might be something to check out

 

If it happens every now and then it might be this. Theres something that I forget the name of that has something to do with the timing tension that loses its purge when it sits for a few hours or so. My sis had a Lexus that would do it fairly regularly. Like the moment you crank it would sound like you were rubbing a stick against a wash board really quickly for like 2 seconds

Edit: Oh yeah. Our timing chain tensioner is hydraulic. Meaning it is ran by oil. Not saying it is the issue but I would take a look at your timing chain tensioners.

 

You need to get under the hood while it is happening and pinpoint the source.

Perhaps have someone in the driver's seat and fire it up while you wait for the noise.

 

These are all great ideas! Will definitely check these out and report back, do not want to take to the dealer if its something I can fix....generally pretty handy.

 

Turns out it was loose heat shields!

 

I had the same problem. Got a can of penetrating oil soaked the three studs that hold it in place. The one over the converter is a challenge. This is a 09 Tacoma, left it there for most of the day, put a socket on it and tried to tighten it without breaking the stud. It moved slightly so did the second one. The one over the converter had lots of exposed thread, I had a nut that would fit, placed some washers on it large enough to go over the existing nut. Added a washer to hold them on and thigh tended the nut onto the existing exposed thread. No more rattles.Be patient as those studs can be broken easily, lots of oil.hope this helps.

 

Sorry folks in loosening the nuts on that heat shield I worked the nuts back and forth that is tighten and then try to loosen it. The penetrating oil did the job and as I said no more rattle.