6.2 Motor Chirp - may be pulley bearing or vibration squeak

Edis06

Member
35
15
8
Location
Florida
My HMMWV is nearly restored and fully sorted. Enjoying it every day. However, I've now run into another bug: There is now a low RPM chirp coming from the engine area. It chirps at every revolution, so I do not think it's a belt (belts rotate slower due to size so I've seen most belt chirps occur at the time a part of the belt reaches the pulley in question). Just to be sure, I sprayed some belt eze on all the belts and didn't help.

The chirp sounds more metallic, like a loose bolt caused by vibration, in which case it would also occur at every revolution.

I am thinking it may be a bearing for this reason. Also, I remember hearing a "rattling" sound at idle before this sound started a few weeks ago.

However, the repetitious chirping sound only occurs (loudly) when idling in D at intersections and sometimes at idle in N. Obviously, the frequency of vibration is more pronounced in D with the foot on the brake, so this is why I was leaning toward the lose bolt theory.

The sound totally disappears with even the slightest amount of gas.

Are there any common places where this sound would occur? I suspect it won't be easy to find.
 

HoveringHMMWV

Member
62
47
18
Location
AL
I had the same "chirp" sound emanating from the engine at idle (once every belt rotation). I deduced that a bearing, having more rpm's, would've produced more "chirps" per minute and therefore the belt might be the problem. Changed out the serpentine belt and the "chirp" went away. My belt was the original and I figured it needed changing anyway. Kept the old one for roadside emergency repair.
I'll let others with more knowledge "chime" in.
- HoveringHMMWV
 

Edis06

Member
35
15
8
Location
Florida
I had the same "chirp" sound emanating from the engine at idle (once every belt rotation). I deduced that a bearing, having more rpm's, would've produced more "chirps" per minute and therefore the belt might be the problem. Changed out the serpentine belt and the "chirp" went away. My belt was the original and I figured it needed changing anyway. Kept the old one for roadside emergency repair.
I'll let others with more knowledge "chime" in.
- HoveringHMMWV
Thank you for the reply! I have the older 6.2, so I have V belts, not a serpentine. I'm going to investigate further this afternoon.
I'm wondering if anyone knows if the harmonic balancer or any bearings next to the crank are known to fail. It seems to me I'd hear "something" if I gave it slight amount of gas if that were the case, but NOTHING. It completely disappears if I give it even a touch of gas.
 

Edis06

Member
35
15
8
Location
Florida
Thank you for the reply! I have the older 6.2, so I have V belts, not a serpentine. I'm going to investigate further this afternoon.
I'm wondering if anyone knows if the harmonic balancer or any bearings next to the crank are known to fail. It seems to me I'd hear "something" if I gave it slight amount of gas if that were the case, but NOTHING. It completely disappears if I give it even a touch of gas.

Also, I looked at all the pulleys while running today and all of them are smooth, except for the main pulley at the crank - the one with 4 belts at the bottom. It seems to wobble very, very slightly. May be an optical illusion but it's noticeable.

Do these fail and when they do, will they produce these symptoms?

Will a harmonic balancer cause a slight wobble?
 

Milcommoguy

Active member
612
193
43
Location
Rosamond, CA
Ahh... the squeaks, wiggle, wobble and gremlins. I too can't stand noises that don't belong. Real short stories... so gather around the camp fire.

The rattle.
This was a crazy one. At idle, ping ping, pang ping, ding ding, dang ping. Thought I had to live with it, till something blows up or fall off, But that's not how I roll.

Got the creapie crawler and stethoscope. Noise is coming from muffler as in what the heck. Maybe ??? rock flipped up into tail pipe. Remover extension and elbow. NO luck and the ding dang noise is still coming from the muffler. OK , I am a little smarter than a muffler (in my mind) so maybe a weld broke on a baffle.

Can't and won't live with this noise. Shut truck down and tapped around on bottom of muffler. Tap... ding. Tap... donk. Tap... Ping. OK ok... this muffler thing is coming OUT. After messing, twisting and a naughty word or two... it is on my chest and we are rolling out.

Something is it there. Sound like a BIG spray paint can. Up...chink. Flip it around... doink. Something is in there and I CAN'T shake it out after two beers.

That does IT ! I am going to crack this nut OPEN! Three inch hole saw and Mr. Milwaukee in hand... cut a hole in the end. OK little "F"er try and stay in there NOW. burp.

Boy's and girls... want to take a guess??? Some monkey mechanic dropped a big fat allen socket head bolt in there. When I saw it fall out, all carbon up I KNEW where it could have came from, But I have all of mine in place.

My guess. Kuckle head Gomer flipped in in there during a rebuild or engine swap. Reminds me of a movie ___________________.

Welded back hole slug like new and a little internal modification for more Vrrooom. hehe

The buzz.
At the right RPM and all things equal... BUZZZZ BUZZZZ !! Creapie crawler again. (Has more mileage than the HumV) I don't see or could guess what's buzzing. Block and start truck. Rolling around not to get burned or snagged... it is the modified flywheel and starter nose shield, at the gap where cut. A little tweek fixed that after a week of buzzing .

Wheres the S'mores?

The Ring Ring Ring.
All system GO. Weeks later, ring RinG RING. These can be a bit of pain as the engine need to be running. I get the feeling it's something going around and round. Yea that's it?? 6.2L with belts. Pull the alternator ones. (really two) Start engine and rinG RING and it's not the alternator or phone.

Now that sucks, but yea... BUTT. Now it's easier to poke around with out becoming part of the problem. OH Sweet. Power steering pump! Just what I don't want to mess with.

Said there's a short story here somewhere. LUCKY ME. Bolt backed out of pump and rubbing on the back side of pulley. Easy fix, PITA.

To your problem. Think it thu with process of elimination. Add in all the external variables. In / out of gear??? Someton (it's a word) is moving. There a lot of someton's there. Flywheel, engine or trans mounts, fan centered in shroud, hood mounts, somton loading up / slacking off, mice in glove box, 🤔

Gota get my OCD under control, CAMO

Good Luck and have a story to share when done.
 
Last edited:

Coug

Well-known member
839
396
63
Location
Olympia/WA
to eliminate the belts as cause of the noise, you can use a spray bottle with some soapy water in it. If you spray and the noise goes away, you know it's the belt. If no change at all, then it's not the belts. quick and easy way to eliminate them as a possible source.
Just went through this with my serpentine belt, but could also tell due to the fact it rode up on the edge of one pulley at the same time as the chirp as well. Reversed the belt direction and did constant squeaking. Installed new belt and no more noise.
 

Edis06

Member
35
15
8
Location
Florida
It's the pulley at the crank. It's definitely wobbly, and the noise sounds like it's coming from there. Also, I revved the engine up a bit to 1K rpm and BOY DOES IT SHAKE! Sounds like the hamonic balancer?

If this is indeed where the issue is, what are all the parts that I should replace in there? Any additional bushings, etc.?
 

HoveringHMMWV

Member
62
47
18
Location
AL
This would be the maintenance procedure from the reference that I have handy.

TM 9-2320-280-34
3 - 6 Crankshaft Pulley Replacement
and
3 - 7 Torsional Damper Replacement

-HoveringHMMWV
 

Edis06

Member
35
15
8
Location
Florida
Thanks everybody for your guidance. I just ordered the dampener, the pulley and the crankcase seal. All OEM. This in addition to all new belts should show an improvement. Also an input seal for one of my front hubs - starting to weap.
 

snowtrac nome

Well-known member
1,660
90
48
Location
western alaska
Take a look at the alternator mounting bracketry, i have seen the rear twisted mounts crack and let the front mount bolts brake, if anything is loose in the mounting of the alternator you can have the squeak you describe.
 

Edis06

Member
35
15
8
Location
Florida
Take a look at the alternator mounting bracketry, i have seen the rear twisted mounts crack and let the front mount bolts brake, if anything is loose in the mounting of the alternator you can have the squeak you describe.
Yup, I checked that. Looks good. The slight lateral movement of the crank pulley I think is a dead giveaway in this case. Let's hope it's solved!
 
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