Hi all,
I have a really bad/loud screech coming from somewhere on my 2000 6.8 V10 Excursion and I assume it is in the belt drive system. It almost sounds like a turbo spool except I have no turbo (see video for noise). It first showed up a year ago after I changed the fan clutch. It got better and hardly noticed it all summer and now it's back occurong every day.

The noise occurs most of the time at start up and driving but not always. Also goes away instantly under heavy throttle or higher rpms (above 2500).

I'm trying to pinpoint it but it's hard to tell. And I'd rather not just throw parts at it. So spraying with water seems to make no difference so I'm assuming it's not a belt or misaligned pulley. Took the belt off and the only pulley that makes noise is the alternator (see video) but ONLY when spun counterclockwise. There is some play in the pulley, I'm not sure what is acceptable.

noise while driving
Alternator pulley spinning

Any thoughts on where to go next would be appreciated. I could probably get an alternator and belt tensioner kit from Rock auto for under $200 and likely would resolve the issue but I'd rather be reasonably certain first.

Thanks!

 

Mine makes that exact same noise, but only when it is cooler/cold outside. Anything above approximately 50ish degrees and it's normal.
Anything below, and I have the same noise. Hopefully someone here can help us figure it out as I'm just as lost as you are.

 

Yeah, I live in SoCal so cold here is below 75F.

But interesting you have the same noise. How long have you had it? Anything you can think of that caused it to start occuring? Does it go away under heavy throttle instantly?

Im thinking the next step is to take the belt completely off and see of the noise is still there. I can hear it at idle most of the time (although much queiter) so if it goes away its definitely something in the belt/pulley system.

 

I'd start with a new alternator REMY 92320 {Click Info Button for Alternate/OEM Part Numbers} Remy Gold Info
130 Amps; CAUTION: Pulley Change May Be Required (Only 1 Remaining)
$94.79 $0.00 $94.79

It sounds like it could be a vacuum leak also.

 

Yeah my noise goes away as rpm increases. And like you I'm wondering if it isn't something to do with the belt drive system or the alternator. When I get to work tonight I'll be testing my alternator to see if that is the issue. Next time I am off I'll pull the belt and check for pulley issues. Got a big trip coming up soon and I can't afford to get stranded.

 

Dont know why I didnt try this before but I took the belt completely off and started it up. Absolutley no noise. Varied rpms and nothing was heard. Put the belt back on and the noise wasn't instantly there but after a few seconds and varying rpms it came back. Makes me pretty confident it is something in the belt drive system.

The alternator is newer. Looks like a parts store replacement. PO has lots of receipts but dont see an alternator otherwise I'd try to replace it with that. Charging is fine. Volt output is good. Makes me a bit concerned it only makes noise when spinning by hand counterclockwise. If I'm looking at it correctly the alternator pulley spins clockwise.

So looks like I'll start with alternator. May run to the scrap yard today if I have time. There are a couple excursions there and pull an alternator for $35 if it looks newer. If not I'll order one and report back.

 

I would say the bearings on the alternator are going bad, I had an idler pulley going bad do a similar thing on my Dad's 2002 GMC 1500.

Was a horrid sound at start up, but then after 5-10 minutes, or if you gave it some throttle, it went away.

Definitely a bearing going out, and looks like you figured out it is your alternators.

Could always use a shorter belt and bypass the alternator pulley and see if that makes the sound go away before buying one.

I however have an assortment of belts hanging on a pegboard so I can do odd things like that to check.

 

Very good idea. I have a spare alternator that's hanging around that I can try off a parts truck. Waiting on it to get cold enough to try out this idea as mine is only doing it when it's below 50°F or so. Being so far south has its ups and downs but the warmer weather is a bonus.

 

Unfortunately it wasn't the alternator. I dont really want to keep throwing money at it and hope it goes away. I was a bit leery about the alternator as it only made noise spinning the wrong way but I had to start somewhere. So I'm $100 in and no closer than I was before I spent the money.

Anyone else have any ideas?

I went to the parts yard as they had a 40% off sale over Thanksgiving but one Ex was a v8 and the v10 someone had taken the whole engine. Couldnt find any other ford trucks with the same alternator. But if someone wants some nice 2nd row captains seats there are a pair in the v8 Ex at Lkq in San Bernardino CA. I dont want them or I would have pulled them during the 40% off sale.

 

Might try an old timer trick to find the culprit.

Back in the day they used a type of stethoscope that had a long rod on the end, or like my uncle showed me just a really long screwdriver held to your ear, to figure out what lifter was bad before tearing into the engine.

Maybe using that technique from yesteryear would let you know which bearing is the bad one?

Never done this for a bearing, but I know it works great on finding a bad lifter.

 

Thanks for the input. After having some time to think about it I'm going to rule out the fan clutch first by removing it and running the engine. The noise did start after the clutch change and I always felt it was the clutch or fan but got focused on the alternator as of late.

If that's not it then I will remove the belt again and really take time checking each pulley and may use a listening device. Should be easier to get in there and check things with the fan removed.

 

I took off the fan and clutch and was going to put old one back on. Ran it first with out fan and clutch on. Noise still present. So likely nothing to do with fan or clutch. Noise seems to he coming from passenger side. Ran it again with belt off. No noise. So likely belt drive components making noise.

Notice smoke coming from ac compressor. Seems to be sticking. Need to know if I can bypass the compressor and if so what belt. System is charged so I'd rather just bypass it for now.

If the noise is coming from passenger side it seems only options are compressor (pulley seemed fine in manual test, clutch spun with hand so it's not totally seized. Ac works) or idler, tensioner ,belt.

Since ac was smoking it seems smart to start by bypassing the compressor if possible and see if noise goes away. wont need it for a few months anyway.

 

I'm sure there is a no ac belt out there for a 6.8 but I don't know for sure. I know older fords all offered 2 belts with and without AC

 

I just checked at Napa. There is a no ac belt option for the 6.8

 

Take a read over this forum:
https://www.ford-trucks.com/forums/1...-a-c-info.html