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Big Diesel
10-21-2012, 11:38 AM
Post: #11
RE: Big Diesel
Oh geez, now I'm on the spot to come up with an answer?Rolleyes

There's gotta be a clue somewhere because stuff doesn't get bent all by itself. It's been apart a few times so who knows. My best guess is someone put a pry bar up there to move the crank a bit and didn't see what they were pushing against.
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10-21-2012, 09:34 PM
Post: #12
RE: Big Diesel
Well, even putting you "On The Spot," you come up with some really good answers. That dozer has had so much done to it in the last month that I would guess that you probably nailed that one too. When the oil pump shaft broke they were looking for bad bearings. It was right after that that it wouldn't hold oil pressure anymore.

Thanks again! I'm sure my boss thanks you too! If you ever think that you might like laying in the mud, snow, rain & hot sun while working for peanuts, stop by! We'll offer you a job.

Thanks for using the forum,
Garner

Interested in Mining? Look here: Coal Mining, PA
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10-21-2012, 11:46 PM
Post: #13
RE: Big Diesel
Still not sure how BIG this engine is but the last time a friend wanted an opinion on a BIG engine he was talking about something in a power plant that was made back around 1920. This thing was big enough that it had doors on the crankcase like a ship. You opened it up and went around on an internal catwalk with a drop light and a 6 ft pinch bar to check bearing clearances. The pistons were the size of an elevator car. Top speed? 450 RPM!
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10-22-2012, 09:18 PM
Post: #14
RE: Big Diesel
Now that's what I call an impressive engine! I'd love to see one of them!!! Ours is nowhere near that size. By "big" I meant that it didn't fit in the "Auto" categories in our forum. It is a 410hp, in-line, 6 that turns the normal 2,200rpm. It would probably fit in a big road truck, (Mack, Kenworth, Freightliner) since Cat & Cummins both make bigger truck engines.

The mechanics were putting it back together today. I hope to hear something by late tomorrow.

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Garner

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10-25-2012, 06:28 AM
Post: #15
RE: Big Diesel
Well, more bad news. They put it back together Yesterday and the boss ran it for just a little bit. It started out with 65 psi at full throttle & 25 psi at idle. It wasn't very long before it was at 50 psi at full throttle & 0 at idle.

The boss still thinks that he got a bad oil pump. It was an "after market" pump.

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Garner

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10-25-2012, 10:16 AM
Post: #16
RE: Big Diesel
Ya know, thinking back to basics I have to say that any time I had a wide spread on oil pressure it was because of wear issues. In this case I am seeing some new parts and a toasted bearing but no mention of any crankshaft specs / condition. I mean, this thing has been out in the field for how many years and has how many hours on it and it still has the same problem after all this work? Somebody is missing something in the "everything looks ok" part of this operation. Anyone think to use a micrometer on the crank, cam, etc? Plastic-gauge? Double check the replacement bearings for correct part number? How about using a shop gauge to verify oil pressure? Just grabbing at straws now.
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10-27-2012, 09:42 AM
Post: #17
RE: Big Diesel
Our mechanics are very hard to deal with. They will tell you that everything was checked the "Right" way. But 9 times out of 10; if I have to work on it, I find that it is one of the "Basics" that was missed, as you mentioned. So, all I can tell you is that they "Claim" that it was all checked the correct way.

The oil pressure gauge is a manual type that the line screws in on the filter housing. It has been checked several times with several different gauges. The boss had me run it again on Friday. Still starts up at around 65 psi cold idle. After running for a couple of minutes you loose it.

I seemed to notice one other odd thing that I will check out better on Monday. It seems that it will hold 65 psi until you rev it up and open the bypass. That makes me think that the bypass might be sticking open? I could just be imagining this. I'll let it idle for an hour Monday if I have to to see if it will hold the pressure as long as I don't rev it up.

The boss wants to take the oil pump out of our older dozer and try it to eliminate the possibility of bad pump. I'll let you know if anything else comes up. Thanks for all of the help.

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Garner

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10-27-2012, 10:56 AM
Post: #18
RE: Big Diesel
Interesting idea to recheck that OP.

Short story time:

Years ago I took over a rebuild shop doing air cooled VW engines. (circa 1975) The boss says, "When you get spare time there's a "new" engine over there that we took out of a customer's car because it had an odd noise on start up." An hour later I had it opened up enough to see excess play on the rod bearings but with only a few minutes of run time there was no unusual wear to the naked eye. Two minutes with a micrometer confirmed the last guy had thrown in a set of standard bearings on a crank that was .010" under, which if it had been run long enough might have shown up as low oil pressure. OTOH, maybe not as these cars only had an idiot light set for 10 PSI.

Now, this was an air cooled gas engine so "noise" is obvious. Could you even hear something like that on a big old rattle box of a diesel?
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10-28-2012, 10:41 AM
Post: #19
RE: Big Diesel
Interesting that you should ask about hearing a noise on this big rattle box, PLUS squeaking tracks.

My turn for shot stories:

I think it may have even been the same 355 that we are talking about now that I was running years ago. I heard a slight knock. I called the boss and told him. He came over, listened to it, couldn't hear anything & told me to keep running it. If it got worse, call him. An hour later I called again & told him it was worse. He sent his son to listen to it. He couldn't hear it either & again I was to run it until it got worse. Another hour & I called back. This time a sublet mechanic came out & he COULD hear it. He told me to shut it off so we could start tearing it down before any real damage happened. I didn't have to. It locked up before he finished his sentence.

Running the 455 similar things happened twice. I would tell them that I heard noises that shouldn't be there, they ignored it & the first time they lost a big V12 Cummins & the second time the PTO housing locked up.

So I think that is why the boss keeps putting me on this dozer. He finally has realized that if it starts making a noise I will likely hear it. So far though, it sounds completely normal. I just have to watch the Oil Pressure Gauge & remember not to let it go to an idle. The last time the oil pump went out it never made a noise. I was looking backwards when it lost oil pressure & it just came to a gentle stop. I thought that I ran out of fuel. That was the time that a rod bearing seized.

Time will tell, I suppose? I'll keep you posted.

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Garner

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10-28-2012, 11:03 AM
Post: #20
RE: Big Diesel
Speaking of hearing things, if you are over 40 there's lots of things you can't hear. Just had a discussion on another board about that odd whine your older TV set makes. The noise comes from the fly-back transformer and it's about 15,000 hz. When I was a kid I could follow the noise to the TV department of any store. The newer flat screen sets don't have this so many people don't even notice.

Back on the ability to hear, the other thing that goes away with age is separating one noise from another. IOW, picking up on a single conversation in a crowded room becomes a problem and so does listening to the dialog in a movie over the music sound track. Same goes for picking out that noise in an engine over the rest of the roar. This may be why the older boss figures the punk kid may have sharper ears. Using "protection" helps lower the roar to a point where the ear can once again pick things out. (if hearing damage has not already been done)
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