Humvee Engine Knocking (yes it's actual knocking, probably)

[Retiredwarhorses]

So theoretically speaking, if I disconnect the cold advance from the pump itself, should it sound different?

yes…

 

[jake20]

Hah, now I’m 100% sure that was it. I tried unplugging the cold advance from the pump with that injector disconnected, but was discouraged when the sound remained the same.

I put it all back together, torqued the injector and line back in, and decided to try unplugging the cold advance once more.

Here’s a video, there is massive audible difference between it being plugged in and not:

RWH, thanks again for shedding some experience

 

[Mogman]

AS RWH said it sounds like it is idling too slow

 

[jake20]

Just turned it up a little bit by ear, I’m betting the sound during winter starts is going to be fun as well.

 

[spawn hmmwv]

Hello fine individuals, I started hearing some noises today that nobody likes to just start hearing out of the blue.

Basically, I've had this M1043A2 6.5L for almost a month, been getting it fixed up while waiting for the sf97 to come in. Today, I installed a new oil pressure and voltage gauge, as the previous ones had water intrusion. I take it out for a drive, and I'm about 20 minutes in with the engine at full operating temperature. As I'm driving at around 35-40MPH, I start hearing a very audible clacking/smacking sound, very different than anything I've heard from this machine yet.

I pull over and shut it off and then proceed to look around the engine bay for anything loose, the only thing I found was that the crankshaft pulley has a little bit of play in the rubber. I start it again and rev it slowly a few times. The clacking follows the engine RPM, and is 100% not part of the normal diesel clacking sounds you typically encounter.

So far.. I've read that it can be a few things:

1: Bad injector
2: Cracked piston / head
3: Loose pulleys / bad bearings
4: Other fun things

Trying to narrow down what it is, I took a video and the sound is very evident around the 30-40 second mark:

If anyone's heard this before or has any ideas on what I can check, would be appreciated. One thing of note is that my bottom-most injector line on the injection pump is pretty rusted, so there may be a possibility of air getting in the line? But it doesn't seem to be leaking either. I'll probably start by pulling the injector lines one-by-one and seeing if the noise persists.

hello. I’m replying to the original post because I’m having a similar problem. After running for months without any problems the engine started to make a knocking noise and spitting out a lot smoke. The video below shows the knocking. This engine was replaced 20 months ago and I only drove from 4500 miles. Any suggestions what to check? From the original post some people mentioned injectors, lifter, change oil, etc.
Appreciate any suggestions.

 

[jake20]

hello. I’m replying to the original post because I’m having a similar problem. After running for months without any problems the engine started to make a knocking noise and spitting out a lot smoke. The video below shows the knocking. This engine was replaced 20 months ago and I only drove from 4500 miles. Any suggestions what to check? From the original post some people mentioned injectors, lifter, change oil, etc.
Appreciate any suggestions.

What color is the smoke? White? Black? Take a video of it.

Go to the front of the engine bay and look at the pulley system. Look at each pulley closely while it’s running, are any of them wobbling? Is the tensioner slapping? The pulleys would likely be unrelated to the smoke however.

If it’s white smoke, you may be burning coolant, either blown head gasket or water is getting in somehow

Black smoke at idle wouldn’t really make sense

 

[jake20]

Are all fluid levels good? Mainly oil? Have you tried changing the oil since this started? If not, change it and see if it still persists. Again, doesn’t correlate with the smoke however.

If you want some concrete data, send an oil sample to blackstone labs. They’ll be able to detect any traces of unwanted contents.

 

[MarkM]

When you get on it what color is the smoke and how much of it is there. Could be an injector failing. Get a stethoscope to help isolate the noise.

Mark

Audio stethoscope

 

[DD58]

I don’t do diesel but it sounds like a lifter out of adjustment.


Sent from my iPhone using Tapatalk

 

[Mogman]

Like Mark it sounds like a failing injector to me, bust each line and see if it goes away on one of them.
IMHO it is not "tinny" enough to be a lifter.

 

[MarkM]

Just listened to the 2nd video and I believe it's a stuck open injector. Explains the sound and the smoke. As suggested crack the injector lines one at a time to isolate. If it is stuck open don't drive it as the poor cylinder is getting washed.

 

[MarkM]

Sounds a lot like this knock video.

Injector knock

 

[spawn hmmwv]

What color is the smoke? White? Black? Take a video of it.

Go to the front of the engine bay and look at the pulley system. Look at each pulley closely while it’s running, are any of them wobbling? Is the tensioner slapping? The pulleys would likely be unrelated to the smoke however.

If it’s white smoke, you may be burning coolant, either blown head gasket or water is getting in somehow

Black smoke at idle wouldn’t really make sense

the smoke is grayish. Not black at all. The video below shows. I have not changed the oil since the issue started. I will change it tomorrow. Last time I used Rotela T6 15w40. Today I’ve added sea foam engine treatment. It should help cleaning the injectors.
Hmmwv smoke video

 

[spawn hmmwv]

Sounds a lot like this knock video.

Injector knock

The sound is very similar but the smoke in my case is gray/white.

 

[spawn hmmwv]

Just listened to the 2nd video and I believe it's a stuck open injector. Explains the sound and the smoke. As suggested crack the injector lines one at a time to isolate. If it is stuck open don't drive it as the poor cylinder is getting washed.

thank you. I have no experience. How difficult is to “crack the injectors lines”?

 

[SmartDrug]

thank you. I have no experience. How difficult is to “crack the injectors lines”?

You’ll want a set of injection line wrenches, but nothing to it. Wrench goes in/on, loosen, listen, watch.

 

[Mogman]

the smoke is grayish. Not black at all. The video below shows. I have not changed the oil since the issue started. I will change it tomorrow. Last time I used Rotela T6 15w40. Today I’ve added sea foam engine treatment. It should help cleaning the injectors.
Hmmwv smoke video
View attachment 907578

Not likely to help, if you added it to the oil guaranteed not to help.

thank you. I have no experience. How difficult is to “crack the injectors lines”?

It is best to have an injector wrench like this one.

But you can also use a 19MM/3/4" open end wrench.

They are all a PITA to get to, some are worse,
If it were me I would access and "test loosen" and snug back down as many as I could reasonably get to, then start the engine and when it starts knocking loosen them one at a time 1/4-1/2 turn is all you need (then re-tighten the ones that have no effect on the knock), you will hear and feel the difference as that cylinder goes dead, when you get to the offending injector the knock will cease, hopefully it is one that is easy to get to, if not then go for the difficult ones.
Wear gloves and a heavy long sleeve shirt, there are allot of sharp edges around that engine.
And of course be very careful and aware around the belts/pulleys etc.
They do not need to be super tight just a hefty snug, be careful not to bend/break the nipples that the small return hoses are connected to..

 

[Hmmwvben]

hello. I’m replying to the original post because I’m having a similar problem. After running for months without any problems the engine started to make a knocking noise and spitting out a lot smoke. The video below shows the knocking. This engine was replaced 20 months ago and I only drove from 4500 miles. Any suggestions what to check? From the original post some people mentioned injectors, lifter, change oil, etc.
Appreciate any suggestions.

did you ever find the fix for this issue? I’m having the same exact problem. Thanks

 

[Mogman]

did you ever find the fix for this issue? I’m having the same exact problem. Thanks

Welcome to the SS forums, a knock can be a bad injector, break each line loose one at a time and then re-tighten until you find the injector causing the knock

 

[TOBASH]

As an explanation of Mogman post, you keep cracking injector fuel lines until you find the one that does not affect the cadence/tap. The bad injector line can’t push fuel through so loosening it can’t affect the engine rhythm.