Diagnose the Taco Sounds

My 2008 DCSB OR is making some new and interesting sounds. There has been a little rattle at idle for the last couple thousand miles, but it just picked up a whirr and got a little bit more insistent and persistent beyond idle.

You can listen too it in the following video. Rev'ed it a bit so yall can here it change pitch with RPMs.



I have my theories, and I'll likely take it to a local mechanism, but I thought I would share here in case someone else has heard this before.

 

My money would be on timing chains... Doesn't sound like the rod bearings or valvetrain, but could be wrong.

 

Same sound my grandma's Crosstrek was making. It ended up being the timing chain dragging on the plastic chain guide.

 

Vvti system?
Broken manifold?
Bad cam?
Loose spark plug?

To many possibilities without seeing the truck and running a few simple checks. I would get it to someone sooner than later.

 

yup vvti, just approaching 100k miles.

 

Update!

Was going to replace serpentine belt anyways, so took it off and started truck. Noise goes away. I checked the pulleys and none seemed horrid, but did find some front to back play in a couple, and they were not as smooth as the others. The noise seems to be coming from driver side, so other culprits would be alternator and AC pump. Both have been replaced in the last couple years, but that don't mean much I suppose. The good news is, I suppose, it that it isn't the engine itself. She purred along with just the slightest Taco Tick with no belt on.

So, now I gotta decide how to tackle this. Replace alternator again? Replace pulley bearings? Maybe try to use a stethescope to diagnose?

 

A long screwdriver up to your ear will work just as well.

Don't know why I didn't think of the alt; bearings going out in those will make a bad noise as well. The slapping noise had me baffled. Keep us updated, every once in a blue moon I'll hear a similar noise.

 

I used a long screwdriver, but didn't even have to put it to my ear to determine that the alternator had a nasty hitch in it's bearings. Damn thing was just put in 6 months ago. Now I gotta do it all over again. Well, this time I'll take the time to pick out a proper upgrade replacement.

Thanks for the help y'all. I'll post here when alternator is swapped out to confirm if that was indeed the source.

It's funny how my gut was right, but didn't want to admit it because of the pain of having just replaced that alternator...

 

Glad you seem to have it figured out!

 

Was going to recommend pulling the belt to reduce the amount of spinning things! glad the answer was easily found. 1GR FTW!

 

Success!

Replaced alternator with Toyota remanufactured one, and eliminated the sound. Funny part was that when it first started it up, it chirped and whirred like crazy for a couple minutes. Was totally perplexed, Then as i was under the truck testing for the origin of the sound with a long screwdriver, it gradually quieted and has been quiet since, even after colling back down.

Thanks for the guidance, y'all.