Something rattling in my head

[pcstan]

I just acquired my 2nd M1123, and after cleaning up the fuel system and starting the engine for the first time I'm hearing a rattling or clunking sound coming from one of the heads.

I'm a competent mechanic but I've never worked on a diesel before. I'm thinking about just hauling it to a shop and throwing money at the problem, but I really don't want to. Should I bite the bullet and start wrenching?

What would you do in this situation? How difficult/easy are these 6.5's to work on?

Thanks in advance!

 

[spankybear]

This maybe the "normal" 6.5 sound. When they run I think I hear a pinging or knocking or clunking noise. If you know anyone in you AO with a 6.5 in your area would listen to it and compare. I have also found that these engines seem to have their own personalty to say. One will be a dog, one will run like a race horse and others like someone just woken up. This is my experience.

 

[spankybear]

As how hard are these engine to work on? Guess that would depend your you and how well you use tools. I do not find them hard. However if yours has one of the dang 400 amp alternators... that would make a nun cuss like a sailor.

 

[Mogman]

Welcome to the SS forums, try cracking each injector line loose one at a time on that side of the engine and see if you can narrow it down to one cylinder.
And as Spankybear says some just have a life of their own.

 

[pcstan]

Welcome to the SS forums, try cracking each injector line loose one at a time on that side of the engine and see if you can narrow it down to one cylinder.
And as Spankybear says some just have a life of their own.

Thanks! Hopefully that will narrow it down. I have another M1123 that runs like butter. Every diesel guy that's listened to this one said that something is wrong.

 

[pcstan]

As how hard are these engine to work on? Guess that would depend your you and how well you use tools. I do not find them hard. However if yours has one of the dang 400 amp alternators... that would make a nun cuss like a sailor.

Thank goodness I have a 200 amp alternator. I'm a pretty good wrench but I'm a little intimidated by diesels. I also only have 1 arm, but I have helpful neighbors and roommates! I think I'll roll up my sleeve and give it a shot! Thanks for the input!

 

[pcstan]

This maybe the "normal" 6.5 sound. When they run I think I hear a pinging or knocking or clunking noise. If you know anyone in you AO with a 6.5 in your area would listen to it and compare. I have also found that these engines seem to have their own personalty to say. One will be a dog, one will run like a race horse and others like someone just woken up. This is my experience.

Thanks for the input! My other M1123 runs like butter, but this one is definitely only running on 7 cylinders. There are a couple other HMMWV's in the area and they all run a little differently, so I get what you say about their personality!

 

[spankybear]

Thank goodness I have a 200 amp alternator. I'm a pretty good wrench but I'm a little intimidated by diesels. I also only have 1 arm, but I have helpful neighbors and roommates! I think I'll roll up my sleeve and give it a shot! Thanks for the input!

WOW... Not to poke fun but just too look at things I have heard and said over the year.s.. Man I could use a third arm... You be like Hold my beer. Again not to be disrespectful. Just amazed how people well can adapt. I should stop and think before I complain and just figure out how to adapt.

Don't be intimated by diesels as they are easy. The need fuel, air and heat (spark on a gas engine) The heat (spark) comes from the compression.

Do you have access to a thermal camera? It may help find out what cylinder isn't firing. Look at the exhaust manifold and look for a cool cylinder. If you don't like Mogman said crack each injector line loose from the injector. This is the equivalent to pulling a spark plug wire looking for a misfire.

 

[Gcelevator]

Diesel engines inherently are easy to work on, i would say 10 times easier than gas engines as they don't have all electrical timing and so.
Detroits are far easier and noisy, very noisy.
Check your cold advance. When they start cold, it sounds like a coffee grinding machine or worse.
Follow Mogman suggestion and start working your way from there. A video with audio will also help try to determine where the noise might be coming from. Good luck.

 

[ikoinu]

I had an issue recently with my 6.2l knocking on the top end. Certainly sounded like the valve train.

It had sat for a period of time without starting, and had old diesel in it. Would not start due to a fueling issue. Problem ended up being the fuel shutoff valve that the solenoid actuates was gummed up and would not move, even though the solenoid was actuating. After freeing the valve, cleaning the entire fuel system out and bleeding air from the injectors, it started knocking, especially when it was cold. Likely cause lifter or faulty injector.

Using Seafoam (Disclosure: I do not work for the company ), I poured a 16oz bottle into the oil crankcase, and disconnected the air filter and poured small amounts of another 16oz bottle into the intake manifold (not too much at a time!) until the bottle was empty, this will take a little bit, don't stumble the engine too much.
Ran the engine just above idle for half an hour, and still had a little knocking. Shut it down and left it for a few days.
Next time I started it up (and ever since), knock is gone. Not even a hint of one when cold.

Prognosis: Believe it was an hydraulic lifter in the valve train gummed up with really old diesel, that was sticking in the closed position. The Seafoam cleared this out and allowed the lifter to function normally again. Other cleaning solutions could have the same effect, including a little transmission fluid in the oil.

Note: It is advisable not to put the engine under much load with this amount of cleaning agent in the crankcase, and to do an oil change prior to normal usage.