08 Tacoma 4.0 engine noise… dealer says it’s normal.

And were you able to narrow it down at all, in terms of where it was loudest or seemed to be coming from?

 

Sorry no help here. Every time I listen to the video, I end up falling asleep.

 

No, I can’t really hear it outside over the engine noise. I have yet to crawl underneath to check.

What I know is it is much louder when the motor is cold or hasn’t been started for a day. As it warms up to normal operating temp, it becomes so subtle to the point you can barely hear it, but it’s still just barely there. Only at idle though, while driving it’s gone.

 

How does exhaust sound when this noise is coming from engine bay? Does idle have a miss, or change in coordination with the sound? If idle RPM remains steady, with no miss, thats a good sign.

To me - it sounds like there is an auxiliary or accessory item vibrating against the fender or fire wall. Maybe even a sway bar? These can be difficult to track down, so be patient. Sometimes the noise will only appear at certain RPMs. So this can be a reason it only does it when on cold start - then engine is at a specific frequency, causing the item to vibrate.

 

Sounds like harmonics from a loose component. check your fan or fan shroud

 

Pull the belt off and start the engine.
If the noise is gone, it’s a belt driven component.

Obviously, you don’t want to run the engine for a long time this way. But I will not hurt anything for a short time. This is a common diagnostic technique used frequently

 

Truck runs very smooth, exhaust sounds fine. No misses or hiccups.

I do have a snorkel and trimmed fenders fenders, but I don’t think it’s panel vibration. Sway bar was removed, all body mounts are new, as well as tie rod ends, strut assemblies, upper and lower control arms.

I’ll be giving the heat shields underneath a good listen next time I cold start it.

 

When I had it in for the 200,000 mile service, the tech said all pulleys and anything related to that, (alternator, ac pump, power steering, etc) was good to go. But they did replace the serpentine belt. So that’s not it.

 

Do not trust them! If those bearings have Not been changed they have got to dry and will zing with ease when spin. Not sure what your skill level is but take that belt off and fire it up , that will eliminate anything on the front of engine. And what is your outside air temp? Mine has a hole or crack in the manifold and under 10 degrees it will make extra noise from that and a bit of piston slap . I should be able to compare your video Tommorow am with mine should be about zero.

 

Here's another thought, not sure if you have this on your model year but if you do you may want to check the secondary air pump.

 

This, before anything else! Don’t take someone’s word.