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

[Mogman]

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.

Not exactly, if an injector it is leaking which causes the cylinder to fire early creating a knock, you crack the lines one at a time until the knock stops, then you have found the defective injector.

 

[TOBASH]

Not exactly, if an injector it is leaking which causes the cylinder to fire early creating a knock, you crack the lines one at a time until the knock stops, then you have found the defective injector.

Respectfully. Not all injectors get stuck OPEN. This method I described is exactly how I found a plugged/closed injector that needed replacement.

 

[Mogman]

Respectfully. Not all injectors get stuck OPEN. This method I described is exactly how I found a plugged/closed injector that needed replacement.

Yes but that would cause a miss not a knock.

 

[Hmmwvben]

Not exactly, if an injector it is leaking which causes the cylinder to fire early creating a knock, you crack the lines one at a time until the knock stops, then you have found the defective injector.

I tried that without much success. The 400 amp alternator makes it impossible to reach cylinders 1 and 3 without removing it. I cracked all the others but its hard to isolate where the noise is coming from. The noise is very quiet when first starting at idle, goes in and out when driving, and was temporarily fixed with a bottle of Seafoam in the fuel filter when I changed it.

 

[TOBASH]

Loosen the injector hoses from underneath. Crawl under. Trust me.

 

[Mogman]

I tried that without much success. The 400 amp alternator makes it impossible to reach cylinders 1 and 3 without removing it. I cracked all the others but its hard to isolate where the noise is coming from. The noise is very quiet when first starting at idle, goes in and out when driving, and was temporarily fixed with a bottle of Seafoam in the fuel filter when I changed it.

Can you get the the IP end of the injector lines for 1-3?

 

[TOBASH]

Can you get the the IP end of the injector lines for 1-3?

When I crawled under mine, I was able to reach them.

 

[Northcross]

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.

Mine was making similar noise. Knock became quicker at RPM, blew a white cloud of smoke then lost power and wouldn’t start again.

http://imgur.com/a/8r0QRvH

 

[Mogman]

Again check all you fluids, it sounds like your transmission is slipping badly.

 

[derrickthompson83]

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.

What did you ever find caused the knocking noise ?

 

[jake20]

What did you ever find caused the knocking noise ?

Negative, changed the oil a few times and it went away, best guess was one of the lifters but that's it.