"Marble in blender" sound

[cattlerepairman]

I am always listening for odd sounds amongst the multitude of rackets my truck makes. Lately, when started cold and idling, there is a sound reminding me of a marble/pebble rattling around in a blender. The sound is independent of the transfer case engaged or not and independent of the clutch being depressed or not (me thinks not tranny/transfer case/jack shaft related sound. Bellhousing? Clutch plate? Broken rod bolt head slamming around in the block? (only joking on the last one, I hope).

No clutch/gear change/driveability issues.

I cannot quite locate it; it seems to come from midline firewall area and is best hear inside the cab.

The sound disappears when warmed up; warm, idling, no sound. Back on next cold start.

It is too cold to have fun wrenching outside. I probably need to go listen with a stethoscope and locate it better. Any ideas in the meantime?

 

[Jeepsinker]

Check everything that is belt driven on the engine. I've seen alternators and idler pulleys both make sounds like that and stop when warmed up. Make sure the harmonic balancer isn't coming apart too.

 

[cattlerepairman]

Thanks. Will check.

 

[glcaines]

Check everything that is belt driven on the engine. I've seen alternators and idler pulleys both make sounds like that and stop when warmed up. Make sure the harmonic balancer isn't coming apart too.

I agree. Sometimes sounds can fool you by sounding like they are coming from one place, when actually the sound is actually coming from another place. That being said, you might want to drop the oil pan and check inside.

 

[welldigger]

He doesn't seem to be describing an engine knock. I also second checking everything belt driven. If that doesn't appear to be the problem I would suspect something to do with the clutch.

 

[sandcobra164]

I don't have a clue. Mine sounds rough in the mornings as well when it's cold. My M1028 sounds worse on cold mornings. When they warm up and start to enjoy life again, all that clears and they are good to go!!! Enjoy every step when you get in and out of it. My daddy went on "cruise control" when he retired. It ALMOST got him with a blood clot. He's back working and healthy as could be. Just Drive it!!!

 

[m1010plowboy]

What does it say in the manual...... The G749 has a noise trouble shooting section but I know nothing about your iron.

My last rattle on the M135 was a lawn chair in the back. Stopped a dozen times and laid underneath...wheels chocked.... drove me nuts so I checked every nut I could find. Surprising what comes loose again and again so re-torquing is good.

Then I cleaned out the back and the rattle stopped, silly. Sounded like it was between the cab and the box but it was between the ears. Rattle sounds seem to travel.

Tighten up the new grab bar and you'll be good to go!!

 

[Jeepsinker]

Check all the fasteners that even come close to being in contact with the exhaust system too. That may explain noise until warmup. Metal expands when it gets warm(duh)

 

[Josh429er]

Is it a random rattle or does it correspond with rpm? Correspond with speed? Or just heat? Does it slowely go away as it heats up or is it just all of a sudden gone?

 

[runk]

Fenders ?
Mine had a terrible rattle at startup and idle, that went away once it warmed up, turned out it was a loose front fender. The cold idle on my truck is low (~500 RPM), once it warms up it is closer to 700 RPM. I guess there was some sort of resonance at the low idle.

 

[cattlerepairman]

I can report: all pulleys are tight, harmonic dampener seems to do its job, no noise from front of engine. Nothing out of the ordinary underneath; checked with the engine running. All exhaust components are tight but there is a rattle from the flapper on top of the stack when I grab and shake the stack. Unrelated, I found a slow fuel drip from a line on the secondary filter and fixed it, so that was a good thing.

My major finding: The passenger side headlight bucket and the panel that holds it make a real racket and I am beginning to think that this could be it. The noise is "rpm dependent" in the sense that when I engage the clutch and the rpm drop, the noise (sometimes) appears, even when warm. That could well be the panels rattling. They do seem to rattle less once the engine bay is warm.

Truck goes into storage tomorrow and I won't be able to follow up. I just wanted to make sure I do not have a major issue looming before I tuck her away.

As always, thanks for your help!

 

[Jeepsinker]

That's probably it. Why are you putting her in storage? Poor thing...

 

[hndrsonj]

My right engine side panel is missing the little rubber bumper and it makes the exact sound you have.

 

[Heath_h49008]

Threads like these have been great for helping me track down and fix minor issues. Thank you for the write up on what might have seemed a minor issue.

Heath

 

[cattlerepairman]

That's probably it. Why are you putting her in storage? Poor thing...

Now, now..she will enjoy frost-free, safe and covered storage until end of March. I go see her every few months and start her up. Temps here are dropping, I will be away for two weeks and then snow will be imminent. I do not drive my truck in the winter on our heavily salted roads. No way. She has never seen Canadian winters and I won't teach her!

 

[cattlerepairman]

My right engine side panel is missing the little rubber bumper and it makes the exact sound you have.

Affirmative. No rubber bumpers on the panel.

 

[nk14zp]

I had a rattle in a m818 that drove me nuts. After a week of searching I found the rattle. A hand full of 5/16" bolts I had put in the glove box.

 

[Jeepsinker]

Now, now..she will enjoy frost-free, safe and covered storage until end of March. I go see her every few months and start her up. Temps here are dropping, I will be away for two weeks and then snow will be imminent. I do not drive my truck in the winter on our heavily salted roads. No way. She has never seen Canadian winters and I won't teach her!

Roger that! I just found some rot in a corner of my bed that I gotta fix, so I totally understand.