Strange Cranking/Grinding Sound From Engine

Hey Guys,

Let me first say that TW is the best.. Anyway, I have a 2006 4.0LV6 dc/sb Sport PreRunner. I recently crossed the 125K mile mark, and I just finished up with a bunch of maintenance. Recently I've noticed a cranking/rattling noise coming from the engine when I'm idling and sometimes when I'm accelerating. It doesn't seem to be coming from the belt or the fan. I think it's coming from the motor located below the engine oil filter. Do you guys have any idea what this might be? I took the truck in to a couple places, but they all want to charge me like 100$ for a full engine diagnostic test. None of the mechanics were willing to just take a quick look at my engine and offer some advice or an estimate. Any advice would be absolutely awesome!

(I attached some pictures to give you guys an idea of what I'm talking about)
Oh, and also, this is definitely not the "Taco Tick"

EDIT: Added Recording

 

the "motor" in question is the alternator could be a bad bearing or the pulley is miss aligned do you have the batteries light in your dash ?

 

No battery light, but i just put in a new battery a few weeks ago because the old one died... So maybe the alternator was to blame for that too

 

how hold was the battery ? have the alternator check to see if it output the good voltage/amp

 

The battery was fairly old, it had about 3 years of use. But ya that sounds like a good idea, I'll have the alternator checked out soon. Do you think the alternator could make the cranking noise I'm hearing? I'm not positive that the noise is coming from there

 

If it's rattling as you said, something could just be loose. Get in there and start wiggling stuff around to see if everything is tight. Disclaimer: TURN THE ENGINE OFF FIRST. lol I'm not too sure what you mean by "cranking"... maybe upload a video or sound clip?

 

if some internal bearing are mess up it might be doing some weird noise. if you open your hood does the noise come from the same area?!

 

check if your belt is not crack, worn and have a good tension on it

 

Alright I added a recording if you guys want to check it out. There aren't any obvious problems with the belt, and nothing seemed loose. When I'm under the hood, the noise is coming from the front drivers side of the engine, around the alternator. It usually starts after i rev the engine a couple times, but then continues afterwards while it's idling.

 

Not sure but sounds like a bad timing chain, find a professional diagnostic.

 

could be a bad timing chain (i doubt kind of low millage) ... if you do the timing chain change the water pump at the same time for added peace of mind have a trusty mechanic look at it

 

I'm subscribing as mines doing this too at the moment. Difference is mine has 100k on the odo

 

you can try to pried-out the belt and turn by hand the alternator and some pulley to see if you got some bad bearing or free play in them

 

Mine was doing the same, turned out that the idler pulley near the alternator was going bad. Replaced both uppers for $55 in parts.

You can use a piece of hose, put one end to your ear and the other searching around the motor to pin point the sound. A 6ft fuel line hose is easiest.

 

Pull the serpentine belt and start the engine. If the noise is gone you will know its one of the accessories. If the noise stays maybe internal engine?

 

I like the "remove the belt and crank" idea (but don't run it for very long, zero water circulation of course."

I JUST finished replacing an idler on my daughter's mustang. Was making a sound on the OTHER side of the engine. The idler was pretty rough-running, and when it would grab the belt tensioner had to give some slack, then the idler would release, the tensioner would snap back and produce a near-constant rattling sound. The timing chain has a real hard time rattling, it is not sloppy-loose, it has a pretty stout tensioner on it.

In any case, if it rattles with the belt off, things are more serious. If not, you just have to do a little sleuth-work to figure out what is rattling. Water pumps (for me anyway) rarely rattle, they seem to prefer squealing. But alternators, A/C compressors, maybe the occasional power steering pump, but by far the most common "rattlers" I have found are idlers and the tensioner.

 

any update?

 

Thanks for the ideas guys. No update on the issue so far, I was out of town camping for the weekend. The hose idea is clever, I'll try that out and maybe pinpoint the issue. However, it sounds like I'll have to bring it in to a mechanic next week. I'll keep ya updated!

 

Alright, so I just heard back from the mechanic.. He says the noise is coming from the belt tensioner, and is recommending that i get it replaced. He's quoting 500$ (labor/parts/diagnostic)

 

Just do it yourself. Very easy job.