M923 engine noise

[acesneights1]

Came back from Sussex to this noise. I know YouTube is hard to hear. Sounds like coming from front of motor. Seems to get better if you increase RPMs. At first is sounds like a noisy air compressor running but the air pressure was up and compressor off.
i know this is gonna be another "never seen that or heard that before" because that is the story of my life. Only thing so far is the belts are pretty old and hard but I have been using the truck. I was gonna pull all the belts tonight except the water pump(that is a PIA) and see if noise goes away. Also at idle noise seems to be pulsing a little but gets more steady if you turn the wheels .
I put a stethoscope on it and sounds loudest to me anyway where compressor bolts to engine but I don't hear it if I listen on the CP pump.


https://www.youtube.com/watch?v=eq0LgYkhNAk&feature=youtu.be

 

[simp5782]

. But get excess noise and sounds out of the way first. Could be a cracked coupler especially if you can feel any vibration out of the motor.

Sent from my SM-G935P using Tapatalk

 

[acesneights1]

. But get excess noise and sounds out of the way first. Could be a cracked coupler especially if you can feel any vibration out of the motor.

Sent from my SM-G935P using Tapatalk

It does seem to me that the engine vibrates more that it did. Would I have to re time anything to pull that ? Can I yank the compressor with the Cp pump ?
i got a bad feeling you are right.
it seems to vibrate like an 8.3 Cummins.
is this a common failure ?
i have a junk 250 from an 818 but the piston tore the cp pump off the compressor so not sure if that coupler is damaged. I know there is a bearing in the timing case cover that looked like a abbot cam style bearing. I can't remember how hard it was to pull that compressor off but it was a junk motor so I wasn't concerned about putting it back,,,

 

[simp5782]

https://r.tapatalk.com/shareLink?ur...share_tid=126464&share_fid=20191&share_type=t

NHC250 Air compressor replacement

Sent from my SM-G935P using Tapatalk

 

[red]

Remove the belts from the air compressor then start it up/listen again.

 

[acesneights1]

Remove the belts from the air compressor then start it up/listen again.

Compressor is driven off a gear in the timing case.The CP is driven through the compressor on these so no belt.

 

[red]

Compressor is driven off a gear in the timing case.The CP is driven through the compressor on these so no belt.

Correct, but there are belts attached to drive other components. By removing the belts you remove those other components (fan, power steering pump, etc) from the equation.

 

[acesneights1]

https://r.tapatalk.com/shareLink?ur...share_tid=126464&share_fid=20191&share_type=t

NHC250 Air compressor replacement

Sent from my SM-G935P using Tapatalk

That is a great vid but could you detail the timing a bit more ?
I'm gonna try to download the tm but it's hard to navigate on my tablet.
didn't understand 1-6 thing ?

 

[simp5782]

On the compressor pully behind the water pump belt it has 1-6 vs and 2-6 vs and so on. You need to set it to 1-6 vs even with the mark that is on the compressor housing. Then on your compressor itself the lil Mark on the crank should be at 2 to 3 oclock if your looking dead at it so that its at 9 to 10 oclock if it's on the engine.

Sent from my SM-G935P using Tapatalk

 

[acesneights1]

Correct, but there are belts attached to drive other components. By removing the belts you remove those other components (fan, power steering pump, etc) from the equation.

Oh, I got ya. Yeah gonna try that first ...but I know my luck. It won't be a simple fix.
this truck is supposed to haul a bunch of Marines for a fundraiser in a few weeks and I have no choice but to figure it out it needs and fix it. I am praying something catastrophic is not coming apart inside.
motor always had like a rattle/knock sound under load but one of the other members here was with me over the weekend and said it's the Cummins coconut knock.

 

[acesneights1]

I am a bit confused on what timing the compressor even does on a common rail but that aside so looking at the Tm since you did this already, I clock that scribed line on the compressor shaft to between 9-10 o'clock looking at it ?
is there a possibility of me screwing this up by a tooth ?

 

[acesneights1]

Other things we checked was crank shaft end play on the motor seemed fine, the clutch fan pulley seemed like it was moving more than it should but we also were using a 3 ft pry bar . The alt bracket is loose as well but noise not coming from there. Gonna address that as well and order up some new belts.

 

[simp5782]

When you put the compressor on the crank Mark should be pointing to the driver's side. Looking towards the front of the truck 9 to 10 o'clock

If the compressor is off and your looking at it face on at the mark it will be 2 to 3o clock

Sent from my SM-G935P using Tapatalk

 

[WillWagner]

There is no need to time the compressor. If you pull the accessory drive, now that requires to be put in time of sorts. There wil be no performance issues but if/when you set the overhead, it will be wrong.

 

[acesneights1]

I pulled all the belts except the water pump(which is much more involved). Still here almost like a squeal but sounds better than it did unless I am going tone def from listening to it. Power steering belts are shot. Hard as a rock and cracked. Fan belts not cracked but kinda dry. Alt belts shot too. I really don't wanna pull the water pump belt unless I'm sure because that basically equates to a water pump job.

 

[simp5782]

Nah. Just drop the fan unit off. loosen the 6 bolts knock it back then put the belt on and knock it back tight. I have done 2 on mine without having to add a new crush sleeve. Make sure to lube that fitting on the pump first if you have it.

 

[acesneights1]

Well, I was talking to one of the mechanics at our fleet where Imwork who is really good with these. He said he would give it a listen but that these motors were noisy at idle because of the gear driven accessory drive and that I may be worrying about nothing.
the YouTube is hard to hear but it sounds like a bad throw out bearing at idle then goes away off idle....
maybe it was always there and I never noticed it ?
cant hear it in the truck and I'm kinda deaf.

 

[acesneights1]

Well I got ahold of a guy that works on these old Cummins.
he said the small cam motors are noisy at idle and that mine was idling a bit too low. Basically nothing wrong with. Guess I just never noticed the noise before.

 

[simp5782]

If you want to hear all the weird sounds of your engine just drive around with noise cancelling headphones on and all the windows up. I can hear the taps in the engine and even the internal transmission noise. It makes wonder

Sent from my SM-G935P using Tapatalk