I have a knock that is not metallic, sounds like a miss, but is not.
There is no metal in the filter
Oil pressure is normal.
All injectors checked ok and tried a different set.
Changed the head, runs real smoothe, but knocks still.
Cylinders and pistons are as new, no marks from valves.
Extremely low blowby.
Knock is at half crank speed.
Knock is on pull, less at higher rpm's
When it first started it was only at very light throttle.
Sometimes knocks at idle, sometimes not.
It is getting louder.
Pulled the EZ, no change, just less power.
Knocks more at full warm up.
Is most noticable pulling off in first, quite loud.
Engine has 100k on it, pulls good, good economy.
No dry bearing knock after sitting and starting cold.

Can the VP44 do this???
Or do I pull the engine for bearings??

Cummins service could not diagnosis this one, they had thoughts same as mine. Thought it was the head. They were very helpfull, spent some time on it. Free tested 12 injectors for me.
I don't dare run it to distroy the engine so am losing loads after a slow early year. Any ideas are appreciated.

 

Haulin,
No expert help here but just thinking/typing out loud. If the knock is at half crank speed, wouldn't that mean that it has to be in the cam/valvetrain? Is it possible that a bolt is backing out on a cam or timing gear and hitting the timing cover? Any stethoscope diagnostics to determine where in the engine the knock is? I guess it could be a rod or wristpin making noise only on the power stroke. Can you identify a specific cylinder by loosening the injector lines one at a time to make that cylinder not fire and make the knock go away?
Sorry. No answers. Just more questions. Keep us posted and we'll keep pondering Murphy’s dilemma.

 

I don't know Cummins internals, just going by basic training here...but what type of lifters does a Cummins have? If its half crank speed its probably cam related (or a gear driven accessory). Since you replaced the head, that leaves the cam and lifters. Have you checked the cam lobe lift on all the lobes?

Sorry i can't offer any real help...just a bit of speculation.

Jim

 

Hey, you beat me...lol

Jim

 

One of my hopes is that of several on here that have experienced a rod bearing loss, they might shed some light on how it sounded. I personally have not heard a bad rod bearing on a 5.9. I would not expect it to sound like this.

The noise is at the rear of the engine, 5 or 6. It does not knock loud enough at idle to loosen injectors to find it, I have tried. Have been working on it for a week now. Nothing attached to the head is at fault.

 

Cam lifter pushrods would not only knock on pull. It is quiet as a church mouse with the throttle off. Before tearing it down the valve clearance was on the money, so no lobe problems. They always transfer material and screw the clearance.

This is humbling, I always thought I was quite sharp on engines. Oh well they don't make flat head fords any more anyway

 

Have you thought about a clutch. When we built up the '95 specon we used an air clutch. VERY difficult to engage smoothly. We changed it to HYD around 50K. One day about 70K my dad got off the freeway and started to move and to whole truck started shaking and popping. He was able to limp it home (10 miles) and called a hook. He started looking at the engine but somehow found the center of the clutch had ripped loose. You could not move it by hand. One note it was 10K# with a brownie and has a D70 motor home dual. It breaks the pinion about ever 100K. It is a 180 HP 560#T water/air intercooler VE pumped Recon. We don't hod rod it and wear patterns are good. There are just some frequency/force issues. We had numerous issues with the damening springs on our 4BT we bought new in '85.

Randy

 

Haulin

I have heard minor ongoing rod knocks in cat engines, not so much in cummins. These noises did not lead to metal in the filters for a short while, then it real hits the fan. However, the earlier suggestion of backing off injector lines to locate the noise is a good one. when you take away the combustion pressures, if the knock is in the bottom, it should stop, or at very least lessen to a noticeable degree.
You can also Use the MODIS, as I suggested before, if you have a competent mechanic, or can get your hands on the tool itself, to do a cylinder cutout test. this will tell you what the pump itself is doing. Whta the tool will do, is ramp the engine speed up to about 1200, then knock out a cylinder of your choice, or I believe you can get it to do a complete test on its own. sounds funny as heck while its happening, but it is a good diagnostic.
If the knock can be located by loosening injector lines, chances are you have a partially spun bearing on one rod.
any of these things will help in the diagnosis of the problem. good luck with it

 

Haulin,
Have you done an oil analysis? If it is any type of a bearing problem, it should show up.

Only thing that I can relate your symtoms to is that I had a piston skirt break off which allowed a lot of piston slap on compression stroke.

 

What about the possibilty of a bent push tube (push rod)?

 

I wonder if you should look outside the box....accessories turn at about 1/2 speed...? water pump???? ps/vacuum??????????? usually if you toss a rod or main you will see pretty low oil pressure....hows that? ya know the common rails don't sound like diesels cause they dont use an injection pump....so perhaps it IS the pump...why can't it just be something simple like a cat in the fan??????????

 

The head was changed to another unit. All pushrods were checked for straightness and rub marks. The injector tubes were changed to a newer set. The noise seems to come from the rear portion of the engine. I sometimes think it is coupled with a very slight miss, but not sure.

Knock.... a hard to discribe noise. I can say that I have never heard a bearing knock sound like this. It is more of a deep hollow thump than a knock with a definate hammer sound. I could have worked on it today, but cannot yet justify a pulling of the engine. It is loud enough at driving speeds that I don't dare drive it even empty. It is very definately a one cylinder power stroke event. Yeah I know bad name. It still has full oil pressure.

If I was to hear it for the first time I would say it was an injector. That said, I can see no possibility of the IP doing this on one cylinder only. Tomorrow I will waste some fuel and loosen an injector and load it to try to see which cylinder.

 

I was hoping for a little information from those what work with the vp44 more than I do.

I have located the problem cylinder, it is number three. The knock goes away breaking that injector line.

Question if anyone knows. The vp does have delivery valves. I don't know the actual purpose here, but the service manual calls them delivery valves that the injector lines are attached to. It warns to not turn them.

Ok, what I need to know is if a bad one would cause a misfire and cause the noise I am hearing?

I am down to rod bearing, bent rod, piston skirt, or vp44 as the only possible causes. I can't buy the rod bearing with the sound of the noise and it is on the fire stroke only. With the line loose, no noise at all. And I still have full oil pressure.

I am trying to not pull an engine and go through it for nothing as I did with the head, gets expensive and hard on an old man in the back yard. Any thoughts would be much appreciated.

 

I heard a noise just like you describe on a 6.5 not too long ago, would fade in and out at idle, turned out to be a wrist pin, and it was quite obvious once the oil pan was off. You could poke the piston up about .030" in the bore with a small prybar. I know I've never seen one fail on a Cummins, but it's what I thought of when you described it. Anyway I hope you find it soon and it's as painless as possible. Good luck HID, we're thinkin about you.

 

Too bad there isn't a companion cylinder firing at the same time so that you could swap injector lines to see if the problem moves with the line or stays with the cylinder. I can't see that a compression test would do you any good. The only possible test that I can think of would be to run a dial indicator thru the injector hole and see if you can detect any difference in the travel per degree of crank movement of #3 versus another cylinder. If there is a difference, it could indicate a wristpin or rod bearing but it won't tell you if the problem is the pump. You've got me stumped Haulin. I'm assuming that there's no way to drop the pan w/o raising the motor significantly, right? Otherwise you'd have already dropped it and plastigaged #3.

Keep us posted and we'll keep brainstorming.