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

[jake20]

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.

 

[Hummer Guy]

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.

Its really hard to diagnose exactly what that noise can be on video. I'll start at checking the belt first, rub some dielectric grease on it and see if the noise would go away, if it doesn't, then that eliminate it from being the belt. The next thing I'll check is the pulleys, injectors, and generator. When I first got my truck, the generator had a very loud clicking noise. Hopefully someone else have more info as to what that noise is, but I'll start diagnosing from the easiest thing first

 

[Mogman]

Sounds like a lifter to me..

 

[jake20]

Alright so I did some more poking around and yanked two injector lines off the injectors. I started with a random one, just to see what to expect. Engine oscillated as expected, still heard the sound. Then I put that one back, started it, still heard the sound and the engine had a few moments where it oscillated and chugged like a steam train, likely the air I just introduced.

After that, I pulled the one that has the rust on the line coming out of the injector pump, pretty much the same effect. The line itself doesn't leak.

What I did notice though, is that while the noise follows the engine RPM, it is actually inconsistent. It seems to get loud, then go away for a few seconds, then come back quieter, etc etc.


EDIT: @Mogman if it is a lifter, I've heard of people driving around with lifter ticks for years, know if this deteriorates other parts by not replacing them?

 

[Maxjeep1]

I watched a video on 6.5 knock and I would have bet my life on it was done! Turned out to be a bad injector. I would do anything that I could to diagnose it right

 

[jake20]

I watched a video on 6.5 knock and I would have bet my life on it was done! Turned out to be a bad injector. I would do anything that I could to diagnose it right

Yea I've heard that bad ones can cause it to sound like a bunch of monkeys banging sticks around. A new set of 8 off fleabay looks to run about $270-$350. I just don't want to replace them all and then still end up hearing the noise

I guess that's what I signed up for

 

[Maxjeep1]

Yea I've heard that bad ones can cause it to sound like a bunch of monkeys banging sticks around. A new set of 8 off fleabay looks to run about $270-$350. I just don't want to replace them all and then still end up hearing the noise

I guess that's what I signed up for

So what are your options? You could remove injector lines until it goes away?

 

[jake20]

So what are your options? You could remove injector lines until it goes away?

I'm probably going to try doing so before getting new ones. I had a friend tell me I should change them all regardless as soon as I got the truck anyway. I guess it's sanity thing too.

 

[MarkM]

Pick up an inexpensive
Stethoscope to help localize the knocking. A bad injector could be the culprit. I had picked up two nos injectors for 40 bucks shipped from flyaway just in case I may need them in the future.

mark

 

[TOBASH]

Run a tank of bioDiesel and see if that clears it up. BioDiesel is a surfactant that cleans engines and injectors. Problem is that it eats rubber parts.

 

[Mogman]

Do not change the injectors before troubleshooting them, open each injector line while it is running, IF there is a bad injector the knock will stop when the bad injectors line is "broken" then just replace that injector.
I have heard several Detroits with bad injectors and the knock was always much "deeper" like a bad rod and gets worse when accelerated, this is much more "tinny" like a bad lifter.
I would release the belt as a first step just to make sure it is none of the accessories causing the tapping sound.

 

[Mogman]

If you had an injector line rust through you would loose a cylinder (read engine miss) and you would have fuel coming out of the busted line, not likely the present problem.

 

[Retiredwarhorses]

seen this issue many times from auction trucks, lazy lifter….

 

[Mogman]

You have changed the oil and filter yes?

 

[Maxjeep1]

You have changed the oil and filter yes?

When did you become a staff member/moderator?
Congratulations!

 

[Mogman]

I volunteered to moderate the new FAV forum to reduce the increased work load to the moderators and admin.

 

[jake20]

Pick up an inexpensive
Stethoscope to help localize the knocking. A bad injector could be the culprit. I had picked up two nos injectors for 40 bucks shipped from flyaway just in case I may need them in the future.

mark

Going to try the old screwdriver-to-ear method against several spots on the engine to see if I can locate it

 

[jake20]

You have changed the oil and filter yes?

Was actually on the list to do after I get my injector pump rebuilt/swapped, since the bottom half is rusted and the throttle sticks. Figured I'd rather change those two after I introduce particulates while changing parts lol. I've got a wix 51060 and shell rotella ready to go

 

[Mogman]

I do not mean to be harsh BUT the very first thing you should have done was change the oil, if you bought that truck from the gov. you have NO idea how old it was or even if they used the right oil to begin with, not wanting to contaminate it later is no excuse, in that case just change it AGAIN, oil is CHEAP engines are not, in fact you should have changed ALL the fluids and filters the very FIRST thing, before trying to impress the neighbors.
Off the soap box now...

 

[Mogman]

Now it is likely you have some type of cantamination in that "lazy" lifter, hopefully a good oil change and some run time will clear it up or if not you have cost yourself some unnecessary repairs.