Update: Tell me I dint need an engine. (New video)

New video
https://youtu.be/r_QioQmOoZw

Old video
https://youtube.com/shorts/Msm3mFsIiNI?feature=share

After the mechanic ran a full engine and compresson test and checking everything possible at my request the noise is complete my gone and the 4.0 V6 is running like a top. All of that squealing and knocking was coming from the alternator. So I just paid a wild amount of money to have an alternator replaced and I am happy with it.

I had everyone tell me everything from rod knock, to lifters, to piston slap, and crank bearings. Everyone was wrong and im happy about it.

 

First for me, hearing an alternator sound like that.

 

I know right. Its kinda silly.

 

At least it's fixed

 

A super helpful noise isolation tip I saw posted here on TW was to remove the serpentine belt and then run the engine. You can do this for a couple of minutes if you start with a cold engine without issue.

Glad you got it resolved, OP. When my alternator went, it had the good grace to completely seize up while parked in my driveway. It was painfully obvious which spinny thing was no longer spinning.

 

I’ve seen em look like they were used as a boat anchor for 10 years, then installed, and still working perfectly fine. Then some not even last 2 years, still looking much cleaner than everything else in the engine bay.

 

Well, you don't have lifters so it couldn't have been that.

Seriously tho when diagnosing an engine noise I always take loose the belts to take those rotating bits out of the equation. Can't say I've ever heard an alternator like yours but they can get pretty squirrelly sounding.

 

Did you try to un-plug it and plug it back in?

 

I've seen alternators with a decoupler pulley make that kind of noise when the decoupler pulley goes bad but I didn't think 2nd gens had that design alternator.

 

Me too.

 

Yeah, a wooden dowel as a mechanics stethoscope as well as pulling the belt off would of been cheap easy diagnosis tools. Its how I found my bad alternator.

 

Yes I know. But that isn't what I asked him to do. I was spooked and wanted all the diagnostics.

 

Wow you could have fooled me in thinking it was anything but an alternator.. you see new things everyday lol

 

If he was a good mechanic, the belt would of been the first thing pulled off for a noise thats RPM based.

 

I understand that you disagree with how I handled it, but I live under a different set of conditions. He is an exceptional mechanic and gave me exactly the services that I asked for. I am not concerned with the extra money. I wanted the full data set on everything available in that motor and driveline, and that is exactly what I got. I am in northern Alaska and am often in places where the tow charge would cost 4 grand. This time or year I may even have to call out over satellite for rescue in some weather situatiobs. The same service would have cost 4 times that price in coldfoot or dead horse.

 

Thanks for posting, that may save someone a nice chunk of change one day.

 

OP you did just fine. And thanks for the follow-up.

 

that noise was crazy!
did you play with the broken Alternator a bit to see if you could "feel" a clunk or anything?
I'd be so curious as to how an alt could make that racket!! ( I know @Dm93 made a suggestion about a de-coupled pulley thingy )

Honestly I probably would not have thought to pull the belt as part of the diagnosis.
learn something new every day, Thanks TW, and thanks OP for sharing.

 

On many newer vehicles the alternator has a pulley with essentially a one way clutch and/or bearing to "decouple" the alternator from the engine effectively reducing belt vibration and chatter.
When they fail they can make various noises (knocking, growling, whining, etc), freewheel and effectively not turn the alternator fast enough to charge, lock up and cause belt tensioner chatter, or in rare cases separate from the alternator.

https://www.knowyourparts.com/techn.../what-are-oaps-and-oads-and-how-do-they-fail/

 

I hope your master mechanic installed OEM Denso because the other ones are iffy.