Intermittent grumbling sound.
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Logistics Pro
Joined: Sep 2014
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From: Bothell & Silverdale, WA
Intermittent grumbling sound.
'08 F-350 6.4 engine. 117k miles. Stock as a clock. Intermittent grumbling/growling sound coming from the front area of the engine when idling. Can be heard with the hood open or closed. Can't hear it when driving. Any ideas?
Thanks in advance.
Thanks in advance.
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Logistics Pro
Joined: Sep 2014
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From: Bothell & Silverdale, WA
I'm not experienced on these particular engines, but what I'm hearing is like a ball bearing going bad. I guess some of the deep rumbling sound is lost in the video, but it's very prominent standing next to the truck. The Ford stealer wants $750 to replace the water pump, tensioner, and belt, and $550 to replace the A/C tensioner and belt, so I'm wondering just how much of this I could do myself. The diesels I'm used to working on, you just walk right up to them.
Laughing Gas
Joined: Dec 2012
Posts: 1,035
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From: Alberta
I'd probably remove the serpentine belt then spin all the idlers and water pump and alternator by hand. If you have a bad idler you should be able to tell when spinning by hand. It'll sound dry!
Senior User
Joined: Apr 2012
Posts: 394
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From: Cottage Grove
Could very well be a belt tensioner... Start there and with pulleys.
No it does not sound egr related... If its not external it could be broken/bent/damaged rocker arm or a lifter starting to fail. Usually with rocker arm issues you will have a popping out of the intake that gets more pronounced as the motor warms up. That said, a lot of 6.4s won't sound any different at all (even with a cracked piston they will run just fine). Does the noise change as the motor gets up to operating temp? If you jump the starter does it have an even crank? How much blow by does it have? Once its up to temp if you unscrew the oil fill cap and set it in the hole does it blow out?
It could also be as benign as a fuel knock... My truck does it when they first switch over to winter fuel. Not exactly the same noise, but very similar. The noise comes on right around 120* and goes away completely at around 150*.
Definitely check the belt tensioner though, they make all kinds of crazy tapping noises when they go bad.
No it does not sound egr related... If its not external it could be broken/bent/damaged rocker arm or a lifter starting to fail. Usually with rocker arm issues you will have a popping out of the intake that gets more pronounced as the motor warms up. That said, a lot of 6.4s won't sound any different at all (even with a cracked piston they will run just fine). Does the noise change as the motor gets up to operating temp? If you jump the starter does it have an even crank? How much blow by does it have? Once its up to temp if you unscrew the oil fill cap and set it in the hole does it blow out?
It could also be as benign as a fuel knock... My truck does it when they first switch over to winter fuel. Not exactly the same noise, but very similar. The noise comes on right around 120* and goes away completely at around 150*.
Definitely check the belt tensioner though, they make all kinds of crazy tapping noises when they go bad.
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Logistics Pro
Joined: Sep 2014
Posts: 4,920
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From: Bothell & Silverdale, WA
I replaced the serpentine belt, belt tensioner, and one idler (didn't know there were two). The tensioner and pulley were ok, the one idler I replaced was starting to go South. No apparent slop in the water pump. The grumbling noise is still there, warm or cold. Blow-by is negligible when cold, more pronounced when thermal equilibrium is reached. To me the grumbling sounds too deep in tone to be an alternator bearing. Maybe the A/C clutch or tensioner? What does the blow-by suggest to you?
First video is cold idle:
https://www.youtube.com/watch?v=CGK8...ature=youtu.be
Second video is hot idle:
https://www.youtube.com/watch?v=Edlv...ature=youtu.be
First video is cold idle:
https://www.youtube.com/watch?v=CGK8...ature=youtu.be
Second video is hot idle:
https://www.youtube.com/watch?v=Edlv...ature=youtu.be
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In the second video (engine warm) you can definitely hear the intake thumping - mine sounds exactly the same. Is that a healthy sound? Is the thumping that everyone is talking about much more extreme or similar to this?
Sorry Mixer, I'm borrowing your videos to compare the way my truck sounds to yours...
Sorry Mixer, I'm borrowing your videos to compare the way my truck sounds to yours...
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Logistics Pro
Joined: Sep 2014
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From: Bothell & Silverdale, WA
I might add to my video post that the engine seems to have no performance issues at all. Getting 12-13 mpg with 4.30 ratios at highway speeds (except during regen).
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tykateexcursion
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Nov 27, 2012 10:02 PM