Mechanical Cummins ISB 6.7 Knock/Clatter?

Jonathan · May 22, 2018

Hello and good afternoon,

I purchased a 2008 Freightliner M2 with a Cummins ISB 6.7 in it.

The engine has a general clatter/knock that I can't identify.

I took a video and will link it below. Is anyone willing to hazard a guess before I take it in?

Thanks for your time

BigStickJr · May 22, 2018

You can put Detroit filters in it.
You can even paint it green.

It’ll never run like a Detroit.

Jonathan · May 22, 2018

Hahah! Don't disagree there.

piper1 · May 22, 2018

Sounds like a typical 6.7 that isn't the newer common rail injection type coupled with a typically noisy Cummins air compressor. I don't hear anything to worry about in the video.

BigStickJr · May 22, 2018

Right before I retired I bought a tool to detect noises. An electronic stethoscope of sorts. You put on headphones wand point it around looking for air leaks, etc. maybe called a Whistler ?
Less than $200 at Zoro.com under instruments I believe.
I bought it to detect inaudible air leaks. UTube showed it to be worth the investment.
Not sure if it would isolate a particular noise but worth looking into.

Or if you dropped the belts, you could eliminate belt driven accessories.

A skilled mechanic can use a long extension touching areas to pick up noises or vibrations.
I never learned that skill.
If it’s a common Cummins problem a Service Guy May diagnose it by doing a walk around.

Good Luck.

BigStickJr · May 26, 2018

Did you ever get another opinion ?

Jonathan · May 26, 2018

So the truck went in for a basic PM, and as I was leaving the lot, I saw a technician walking across the lot... I asked him, "Hey there boss, can you spare a second and listen to this '08 ISB Cummins idling?" he replied, "Yeah, absolutely what's up?" and I said, "You hear anything abnormal?" to which he replied, "Yeah, I'm hearin' a little clatter there..."

I said, "What you think it might be?" He said, "Without diggin' in I can't say for sure, but doesn't sound too serious."

I said, "Okay so it's not like she's on her deathbed..." and he said, "Nope... If you want we can take a look around next time it's in."

So... Just a diesel tech's opinion after hearin' it run for about a minute.

It's got a sound, but it's not super serious at this point. It honestly sounds like the air compressor is running when it's not. It's identical to that sound.

I also had the valve lash set about a year ago so I don't think it's that... But sounds upper valve train-ish.

I'm not too worried at this point as it's not throwin' a code or lacking power.

Will advise as situation progresses.