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Discussion Starter #1
So, I have a perplexing issue with our 2012 Dodge Grand Caravan. The only way to explain it is that the engine kind of sounds like a diesel engine when it accelerates, with a whining type sound. The serpentine belt was removed and the engine run and there was no change in the noise. The timing belt/chain was replaced along with all the parts associated, except for the camshaft actuators. The noise got a little quieter after that repair, but it is still there. Mechanic used a stethoscope and the sound appears to be coming from the back of the engine towards the passenger side. The noise happens whether the car is in gear, neutral or park. We have now just had the transmission fluid flushed and changed. Thoughts?
 

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Yes, check for a cracked flexplate, not easy to do, but not too hard either.

Cracked flexplate will make a knocking sound.

Here, what to look for:

60221
 

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Discussion Starter #4
Yes, check for a cracked flexplate, not easy to do, but not too hard either.

Cracked flexplate will make a knocking sound.

Here, what to look for:

View attachment 60221
Thanks. My mechanic said that the sound for the flexplate should be a ticking sound and this is not a ticking sound. Could a bad flexplate make a different noise?
 

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Thanks. My mechanic said that the sound for the flexplate should be a ticking sound and this is not a ticking sound. Could a bad flexplate make a different noise?
Flexplate noise is more a knocking noise, like a bad piston rod.

But, noise changes as the flexplate cracks gets worse.
 

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Discussion Starter #6
Flexplate noise is more a knocking noise, like a bad piston rod.

But, noise changes as the flexplate cracks gets worse.
Ok. This is more like a whining sound. Thinking it could be a bad cam bearing, but haven't been able to test that. I believe he said the sound is coming more from the top of the engine compartment, passenger side.
 

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1997 Plymouth Grand Voyager Rallye
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Flexplate noise is more a knocking noise, like a bad piston rod.

But, noise changes as the flexplate cracks gets worse.
I had a 1964 Chevy that had a rod knocking sound. I jacked up the engine off its mounts to free the oil pan. Inspected every lower engine bearing, plastigauged the bearings.
Ended up being loose torque converter bolts. FML, took 5 minutes to tighten those bolts once I found the actual problem.


@epeschel75, maybe one of the overhead cams? I haven't had a Pentastar Engine apart, are there any gears on the camshaft? Sometimes a DOHC will have only one camshaft per head driven by the timing chain/belt, and the other camshaft is driven by a helical cut gearset between the two camshafts. This fits with the "whirring" description.

Perhaps an exhaust leak. That would explain a "diesel" noise. Maybe if you disable one cylinder at a time while the engine is running, you will find that a particular cylinder is causing the noise or affects it more than the others. You'd want to disconnect one spark plug wire at a time on the rear cylinder head to listen to changes. This will throw a Check engine light, and the engine will certainly run rougher every time a cylinder is disabled, but you are listening for just the noise to stop. Be careful doing this. You don't want to run the engine long on 5 cylinders, and you don't want to shock yourself.
 
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Discussion Starter #9
I had a 1964 Chevy that had a rod knocking sound. I jacked up the engine off its mounts to free the oil pan. Inspected every lower engine bearing, plastigauged the bearings.
Ended up being loose torque converter bolts. FML, took 5 minutes to tighten those bolts once I found the actual problem.


@epeschel75, maybe one of the overhead cams? I haven't had a Pentastar Engine apart, are there any gears on the camshaft? Sometimes a DOHC will have only one camshaft per head driven by the timing chain/belt, and the other camshaft is driven by a helical cut gearset between the two camshafts. This fits with the "whirring" description.

Perhaps an exhaust leak. That would explain a "diesel" noise. Maybe if you disable one cylinder at a time while the engine is running, you will find that a particular cylinder is causing the noise or affects it more than the others. You'd want to disconnect one spark plug wire at a time on the rear cylinder head to listen to changes. This will throw a Check engine light, and the engine will certainly run rougher every time a cylinder is disabled, but you are listening for just the noise to stop. Be careful doing this. You don't want to run the engine long on 5 cylinders, and you don't want to shock yourself.
Thanks for the info!
 

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2013 Dodge Grand Caravan
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Thought I would try and post a short audio of the noise. Maybe this will help as well.

Van Noise

Nothing about that sounded even remotely like a diesel. Could be oil pump whine. I've heard a few people have had issues with them going out and whining because the variable pressure solenoid had failed. If the noise appear to be coming from down low, suspect this.

If the noise is up in the valve covers, check rockers.
 

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Discussion Starter #14
Thank you everyone for the suggestion. We found the problem and the van is fixed. We did have an issue with the timing chain. However, it was discovered that after fixing the timing chain issue, the noise went away when the serpentine belt was off, where before it stayed. It was then discovered that the alternator was bad. So, changed the alternator and the van is quiet again!
 

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Meh, now I feel dumb. I did 3 alternators last week for customers complaining of a whining noise... how did I not think of that. :p Glad you got it figured out.
 

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Meh, now I feel dumb. I did 3 alternators last week for customers complaining of a whining noise... how did I not think of that. :p Glad you got it figured out.
Don't feel dumb. I originally posted that the noise happened with or without the serpentine belt. That would eliminate the alternator. It wasn't discovered until today that the sound now went away with the serpentine belt off.
 
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