So today I noticed I had a loud rattling noise coming from the engine. It's rather loud on top of you open the hood and sounds like it's coming from between the turbo and fan in the center and it's also heard from underneath the truck. Somewhere in the belt area. I took a couple videos were the sound is audible. But for some reason it won't let me upload them. It sounds like a rattle

 

Most likely and idler or tensioner pulley...tensioner pullers are a fairly common failure on these trucks. Has your belt been squealing at all?

 

It sounded a couple weeks ago like there was a quiet squeal but then it went away.

 

Check your tensioner pulleys asap, there are two...one for main belt and one for a/c belt....when these fail the belt fails and can grab onto stuff in the process and cause a fair bit of damage. Also while you're in there look at idlers as well.

 

This is a picture from underneath. Is the the tensioner pulley and is it supposed to look angled like that?

 

And this may be a dumb question but how do I check them

 

Nope....supposed to sit straight....that tensioner is bad and a ticking time bomb.

 

With belt off spin idler pulleys and listen for bearing noise....check for play in pulley itself...any movement is bad....replace pulley in that case.

 

How many miles on truck? If it were me i'd replace a/c belt tensioner as well while I'm in there as main belt has to come off to get to it. I did bolt a/c and main belt tensioners as well as idler pulleys and new belts on my truck around 160,000 km give or take.

 

I just hit 122,000 miles. So the one in the picture is the main tensioner pulley?? Where is the ac tensioner you are referring to?

 

Top left of your photo is your ac compressor clutch, that is a separate belt , idler for that belt will be buried in behind main belt tensioner pictured in photo. Hard to see till you get main belt and tensioner off.

 

Ok I appreciate it. As soon as I looked under my truck that tensioner caught my eye as not looking right but I wasn't sure. I just replaced my alternator about 5k miles ago and don't remember it looking like that but don't recall entirely either. Hopefully that's the only pulley wrong. Is there others on the main belt system that are prone to doing this.? And do you think that's the noise I'm hearing? Kinda sounds clunky and like something loose and rattling under there

 

Almost positive that's what it is. If you start truck and crawl under and look at that tensioner , my guess is you'll see it rattling around pretty good, which also means it's very close to failing altogether. There are two idler pulleys on main belt , check those for noise and play with belt off and replace accordingly. Also while you're in there replace tensioner pulley for ac belt as it may not be far behind the one that's already failing. Like I said when I did mine I replaced both tensioner pulleys and both idler pulleys while I was in there. They aren't that expensive , and now I know they are all new and good.

 

Ya that's what I was thinking but as I ran the truck and looked at it, it didn't move at all

 

Ok I stand corrected after just walking out and looking again, I can see it vibrating. Not violently shaking like I would think but just enough movement to make a noise