Fluttering Noise - Need Help

[Mz202]

Hoping someone might have some insight.

I've been looking at purchasing a 6-speed 06-07 5.9. Looked at one yesterday that has 180k. Owner has maintained it and took care of it. Has new injectors, new front end, and he's done regular maintenance (filters/fluid changes) on it. Hasn't been towed heavy with. A fishing boat every now and then.

The truck drove well, shifted well, has no leaks, and has zero blow by. The one little thing I was noticing when I drove the truck, is there was a light fluttering noise coming from the drivers side engine bay...seemed like it was down low. I was noticing the noise during acceleration. It seemed more noticeable accelerating into and through 3rd and 4th gears.

I haven't owned a manual cummins. Have a 2000 5.9 auto and a 4th gen auto, and have never heard that noise before. I test drove an 03 nv5600 that was making a similar fluttering noise a few weeks back.

Any ideas what I would be hearing? Could it potentially be anything major?

Appreciate any insight or help. Thanks in advance.

 

[seafish]

"Fluttering" doesnt really bring anything to mind when describing "bad" noises these trucks might make.

Unless you mean some sort of "whistling" while accelerating which could indicate a boost leak.

Actually, a boost leak could also be like your lips gping "bbbbbbrrrraaapppp" which is maybe what you are describing as "fluttering" ??

Again that would be under acceleration, or while building boost only.

Perhaps you can record the noise on your phone and then post back??

 

[petersonj]

haven't owned a manual cummins. Have a 2000 5.9 auto and a 4th gen auto, and have never heard that noise before. I test drove an 03 nv5600 that was making a similar fluttering noise a few weeks back.

My guess is that you are not used to the sound of a non-torque converter transmission behind a diesel engine. A manual transmission allows lots of torque to be applied at low engine rpm's because there is no slipping torque converter. One will probably hear more things operating, or things may sound different simply because the noise of an engine running at high rpm (as with an automatic transmission with converter unlocked) will drown out many sounds that may be otherwise heard.

- John

 

[AH64ID]

Could be the DMF or could be the PS pump/hydroboost.

Could also just be the noise difference in a VP vs CP3 truck.

 

[Mz202]

"Fluttering" doesnt really bring anything to mind when describing "bad" noises these trucks might make.

Unless you mean some sort of "whistling" while accelerating which could indicate a boost leak.

Actually, a boost leak could also be like your lips gping "bbbbbbrrrraaapppp" which is maybe what you are describing as "fluttering" ??

Again that would be under acceleration, or while building boost only.

Perhaps you can record the noise on your phone and then post back??

I will try and get a clip in the next few days and report back. I live a couple hours away from the truck.

 

[Mz202]

My guess is that you are not used to the sound of a non-torque converter transmission behind a diesel engine. A manual transmission allows lots of torque to be applied at low engine rpm's because there is no slipping torque converter. One will probably hear more things operating, or things may sound different simply because the noise of an engine running at high rpm (as with an automatic transmission with converter unlocked) will drown out many sounds that may be otherwise heard.

- John

I think you might be spot on John. I've talked to a couple of other guys, both extremely knowledgeable with these older cummins, who said what I'm likely hearing is the cp3.

 

[Mz202]

Could be the DMF or could be the PS pump/hydroboost.

Could also just be the noise difference in a VP vs CP3 truck.

Thanks for the thoughts, will keep those in mind. A couple other guys have echoed that too, what I'm likely hearing is the cp3.