Help dianosing engine rattle

I've got a nice rattle/clank noise coming from the engine on the truck, would like some opinions on what it could be. To me it sounds similar to the IDI diesel rattle you get cold starting with advanced timing, but it's more pronounced and more of a metalic clanking noise for lack of a better work. I have a recording but I can't get it to upload on here. If someone can host it I'll gladly e-mail it to you.

I've had this noise for a while, can't really remember when it started or if it was present when i rebuilt the motor about 30k ago. It's distinctly noticeable from the front and above the engine and very noticeable from underneath. It seems unaffected by timing and the frequency is proportional to rpm. I can't tell if it's at crank rpm or 1/2 that, my guess is 1/2, ie cam speed. Doesn't seem to change in volume or sound with increased rpm or hot/cold engine other than increased frequency with rpm. I thought for a while it was a bad injector, but loosening the lines on each injector has no effect on the noise. The truck runs smooth otherwise and has no apparent problems. I don't have any cuffing or woofing in the intake or exhaust as you would get from a bad lifter, though the turbo could be muffling it. Listening with the stethoscope I hear a distinct metallic clanging noise through any part of the engine, though it seemed loudest through the intake. Couldn't isolate it to a cylinder. I also tried listening for noises while cranking with no fuel and couldn't hear anything....

I did have what i thought was an intermittent high rpm miss but that seems to have gone away after i fixed the timing and may not have been there to begin with.

This engine was rebuilt ~5 years ago, probably 30-40k miles. The rebuild was done by me with the oversight/assistance of an experinced machinist. The heads were done, very good used pistons (estimated <500 miles) except for 2 new ones, new rings, bearings, ground crank, new lifters and 7.3 style rocker arms. It hasn't been run out of oil or seriously overheated, worst it's been abused was getting up to 225* or so for a few minutes, and being run for who know how long with the timing advanced about 7* over spec.

My guess at the moment is that it's something in the valve train. It doesn't sound like a rod knock or anything major but it's hard to be sure. I'm a bit paranoid about truck problems at the moment after the transfer case dying stranded me on I5 in the middle of nowhere and screwed up my memorial day weekend plans.....

Thoughts?

Thanks,
~John

John, I've not been real impressed with the loosen the injector line to listen for the noise to stop trick. I did that several times trying to isolate a bad injector(s) and it also made no difference in the noise. However, once they were pulled and pop tested, I was shocked to see I had three bad injectors.... one of which was stuck open. I said all that to say.......... don't rule out a bad injector just yet. Any way you can test them?

Another option to evaluate the valve train is to pull the valve covers (I know, not fun), looking for anything that is wrong (loose rocker, broken spring...). Then run the engine with the covers off to see if you can isolate the noise if simple visual inspection doesn't reveal the problem.

Heath

I live in the same town as you and have access to a pop tester and could help you try an figure it out

Heath, good info to know. I'm picking up a parts truck in the next few weeks that has a set of injectors though I don't know what shape they're in. Supposedly the pump is new but I don't have any info on the injectors. Mine were replaced along with the pump when I rebuilt the motor but I don't know how high of quality they were....

Devon, I'll probably take you up on that one... A pop tester is one of the few things I don't have yet. BTW, I've got a timing meter and a bunch of other random 6.9 stuff if you ever need anything.

ya i do need stuff and all take the hood off your parts truck if its a slant nose i really need one mines gonna be gone for a month to have the air bruching work done on it. also i was planning on timming my rig with icanfixall maybe i could check it with you and see where it's at my trucks been going through a make over and im almost done all be in the car show in lakeside on the 17 if you wanna stop by.

Get your truck up to highway speed going down hill and shut off your key. See if the loss of combustion makes the noise go away or not. That would help diagnose the fuel system also.

Thats a nice one mel didn't think of that but it's a good idea.

Don't engauge the steering lock when you try that trick John.

Heath

lol ya thats true man that would be horrible

Ok, so I tried doing that tonight and no change. The noise continues independent of key on or off. I also removed the driver's side valve cover and checked everything, no sign of any damage or play anywhere. I checked it running at idle as well, I'm getting good oil flow on all 8 rockers and can't find anything at all wrong. I tried putting a finger on the rockers with it running to see if I could feel any shock or play and didn't feel anything.

Haven't done the passenger side running, though I did check all the rockers and valves 1-2 months ago when i had the cover off to retorque the head bolts. Nothing evident there either.

I also pulled the turbo hose to listen for any woofing with the engine running thinking maybe the turbo might be muffling it. Nothing. I also tried blocking the intake almost completely (at idle) until the engine was starving for air and idling at about 300 rpm. The noise seemed to get louder but was otherwise unaffected. The normal diesel rattle also got louder at the same time, so I'm not sure what exactly I was hearing. It seemed like I had the rattle/clanking noise and then also a fainer ting or clicking at a different time. This was only noticeable with it starved at low rpm.

This is starting to really baffle me.... I convinced it's not fuel related now but something mechanical in the engine. It's consistent, seems unaffected by engine temp or load but does vary with rpm. No rough running or smoke or other issues, no significant overheating & no oil starvation and I know what went into the engine when it was put together.

I thought I had an off and on high rpm high load miss or weak cylinder, but I was never able to find it for sure and it seems to have gone away since I retarded the timing. Not sure what that was, if it was even there.

I've had bad rockers and lifter problems in the past and I don't recall it sounding like this at all, though I think the woofing with that may have covered up any clattery noise... don't remember for sure.

I'm a bit paranoid with this since the last minor irritating problem I had (t-case not going into low range) and put off fixing turned into getting stranded in middle of nowhere, san joaquin valley and spending memorial day weekend driving around in maddening circles in a friend's truck looking for a new t-case. Also had a valve problem on the same truck turn into a thrown rod because I kept pushing an engine that was making odd noises (newly rebuilt motor too.... fun times)

One thing I'm going to check is the lift pump, it occurs to me tonight that a problem there might cause a noise like this.... either the pump or the cam.

Well, it's not the lift pump. Pulled that off and it still does the same thing. Found cracks in the arm of my pump though, so I guess it's good to replace it anyway.....

I took a video and posted it on you tube

http://www.youtube.com/watch?v=2-20pVbeUc0&feature=youtu.be

Let's see if that works. Crumby quality, sorry, but you can sort of hear the rattle especially at the end. Don't watch it too closely though, might make you dizzy. This is cold idle (cold as in ambient temp, ~75* out here) with the cold advance on. Starts at idle and then I reved it up for a bit (can't hear much over the fan, sorry) then back to idle. I then blocked the intake and drug the rpm down a bit. Finally went around under the pan and that where you hear it most clearly.

Retorqued the heads?
Iirc, thats not advised?

Probably not. I wanted to tighten it down a bit (running studs, I had them at stock torque originally and decided to go up to 85 ft/lb) both due to running higher boost and because I though one of the gaskets was leaking...

Not related to this particular problem.

Anyone? Suggestions?

Cannot say for sure...but piston slap....or...wrist pin coming loose in piston or rod...close to a bearing noise...but not quite...
hard enough knock for bearing....
JM2CW

That's what I was afraid of. Any thoughts for further diagnostics?

One thing that I find odd is that it doesn't change at all under power or coasting. I had always heard that a rod or bearing problem was usually easiest to hear when you reved it up and let off on the throttle. It sounds to me to be higher pitched than a rod knock, it sounds more tinny than the dull clunk you hear with a knock. But then, my experience with rod knocking is rather limited.

It also doesn't make a lot of sense to me given that the engine only has ~30-40k on a rebuild, and has never been abused. Could be a flawed part or something for sure, but still....