Metallic Rattle at Idle When Cold

[Hans89]

I have a 2007 6.0 here in Edmonton, AB. Every time I start it, it starts fine…rough as expected from a 6 year old diesel in a Canadian winter, but it’s good. Then I’ll let it sit and warm up. The entire time that the EOT and ECT rise from 50-60 degrees (start temperature when plugged in) to around 170 degrees (174 seems to be my EOT and ECT temp at full warmth), I get a noticeable, metallic rattling from the engine. It is most noticeable from in front if the truck. It seems to come from near the front of the engine, behind the grille a ways…but I can’t be sure. Getting under the hood doesn’t help me pinpoint anything either. Any ideas? Also, this rattle is most noticeable at idle RPM. Once I get going, the rattle goes away until I’m idling again. If I turn on my high idle switch, the rattle also goes away (approx 1200 rpm). Any ideas what could be making this loose rattling sound? It’s driving me absolutely nuts and it makes me feel like my 6.0 is a loose bag of bolts lol

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[dhanna6powerstroke]

I'd pull the belt off and start checking pulleys for play.

[Hans89]

Originally Posted by dhanna6powerstroke

I'd pull the belt off and start checking pulleys for play.

Just so I know, would this be something that's causing damage to me engine (ie. urgent to fix)? Or is it just a nuisance (ie. I can take care of it later)?

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[dhanna6powerstroke]

Could just be an idler pulley causing the noise, but if a bearing fails in a pulley and the belt comes off ot could cause damage.

[twoicebergs]

I get the same noise from time to time when real cold. The bearing seems good on this truck. My previous engine build with a new idler did the same; maybe the noise is from the assembly? For peace of mind give it a check. Use the tool and don't pinch your fingers!

[rdezs]

Metallic rattle at the front of the engine.....I wouldn't run it until I figured it out. You don't really want to have anything take out your radiator, right? And you don't want to get towed home either? I'd start by taking items apart for inspection. You'll find the source. I'd start with the belt tensioner. Rattle at slow speed would indicate a bad bearing. Does it only make the noise with the defroster running in the cab? Go away when you turn the defroster off? If so, could be the AC compressor....it energizes as part of the defrost system, to help remove fog/moisture from inside of your windshield. Alternator bearing a possibility as well.

[Hans89]

Haha well I really don't have the option not to run it daily. It rattles regardless of what's being used in the cab. But only at idle rpm. As soon as any fuel is given, it goes away immediately. Even with only a 150 rpm jump.

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[rdezs]

That would drive me nuts, until I found the source. Well worth the time to inspect all the pulleys, tensioner, etc, etc. Depending on what it turns out to be, you will have your answer on how much longer you can ignore it.

Curious...does it only do this when cold? If so, it could be just a bearing that has excessive play until it warms up. Wouldn't be too unusual in Canadian winter temperatures. If it does it at idle, even after warmed up, I'd dive into it just to make a diagnosis.

I wouldn't ignore it at all. Are you lacking a warm garage to work on it, and wanting to wait for warmer weather? You can always do the old trick for identifying where a noise is originating from. Will only take 2 minutes to narrow it down. Carefully use a long stick, or piece of metal like a really long screwdriver, hold one end against your ear with your fist gripping the end...and carefully place it at various points near the various pulleys, power steering pump, tensioner bracket, etc. Makes a good stethoscope. You'll know when you find it, it'll be a lot louder. You should be able to hear the normal sounds from the bearing operating. A bad one will sound louder and rougher. If nothing sounds obvious, better take a look at your fan assembly. It's about the only thing you can't get the wood stick close to.

[Hans89]

Originally Posted by rdezs

That would drive me nuts, until I found the source. Well worth the time to inspect all the pulleys, tensioner, etc, etc. Depending on what it turns out to be, you will have your answer on how much longer you can ignore it.

Curious...does it only do this when cold? If so, it could be just a bearing that has excessive play until it warms up. Wouldn't be too unusual in Canadian winter temperatures. If it does it at idle, even after warmed up, I'd dive into it just to make a diagnosis.

I wouldn't ignore it at all. Are you lacking a warm garage to work on it, and wanting to wait for warmer weather? You can always do the old trick for identifying where a noise is originating from. Will only take 2 minutes to narrow it down. Carefully use a long stick, or piece of metal like a really long screwdriver, hold one end against your ear with your fist gripping the end...and carefully place it at various points near the various pulleys, power steering pump, tensioner bracket, etc. Makes a good stethoscope. You'll know when you find it, it'll be a lot louder. You should be able to hear the normal sounds from the bearing operating. A bad one will sound louder and rougher. If nothing sounds obvious, better take a look at your fan assembly. It's about the only thing you can't get the wood stick close to.

I agree. It drives me absolutely crazy. It honestly embarrasses me when I have to stop and idle somewhere lol.

To be honest, I'm FAR from a mechanic. I plan on taking it into a diesel shop in Edmonton tomorrow around noon and hopefully they can at least diagnose the problem.

The noise is the loudest and most frequent when the engine is coldest. I can hear it through my front door. As it warms up to the point where the EOT and ECT are 165 degrees or warmer, the noise is less frequent and a little quieter...but still very noticeable at idle. So in summary, yes it still makes the noise even when fully warmed up.

As far as my garage goes, no it's not heated. The truck doesn't even fit in it anyways. And that's just the roof, not even taking the CB antenna into consideration lol

I haven't used the screwdriver method yet. I've tried looking under the hood to even just eco-locate the origin of the noise...but it doesn't sound like it's anywhere close to the top of the engine. It really sounds like the front of the engine, maybe a foot inside the grille. Makes me believe it's something to do with the belt or the fan. But past that...I'd be clueless.

[rdezs]

I'm betting it's the fan, from what you describe. If it goes, it can get expensive if it takes out the radiator....