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Post Number:#1  PostPosted: Wed Mar 22, 2017 10:44 am 
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So about 10k miles after rebuilding the engine the valve dropped, demolished the number 3 piston, and scored the liner. I'm in the process of tearing it down and seeing if I can rebuild it with the parts I have, but I wanted to do an autopsy.

suspects
  • improperly done valve timing. I had just done an oil change and valve adjustment a week or 2 before
  • malfunctioning IP. I bought the car with a destroyed number 3 piston, and bought a donor engine which I swapped in, but the donor IP didn't work, so I put the original on the swapped engine
  • improper IP timing. The timing was never set correctly, just lined up with the mark on the housing. It smoked under moderate load, which I know realize was a very bad sign
  • insufficient top end oiling. The donor engine's head was lacking a hole for the oil gallery. That problem presented itself pretty quickly (and the result was nowhere near as bad as this) so we drilled the whole out, verified oil was flowing, and thought that was good enough

Pictures attached. let me know what you think


Attachments:
File comment: scored bore
DSC_2639 small.JPG
DSC_2639 small.JPG [ 318.78 KiB | Viewed 686 times ]
File comment: spring pic number2
DSC_0376.JPG
DSC_0376.JPG [ 1.72 MiB | Viewed 686 times ]
File comment: the spring. The discoloration was more prominent before accidentally getting oiled during removal
DSC_0374.JPG
DSC_0374.JPG [ 1.44 MiB | Viewed 686 times ]
File comment: combustion chamber
DSC_0372.JPG
DSC_0372.JPG [ 2.12 MiB | Viewed 686 times ]

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Post Number:#2  PostPosted: Thu Mar 23, 2017 6:49 am 
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Just looking at this and trying to come up with an idea as to why. It's interesting that the head of the valve broke off. I was expecting to see that the keepers were missing.
I know that there are a couple of different head gaskets for these that will not allow oil to flow to the top end depending if you have the correct head and block match up. But not sure that "may" be the issue here.
Incorrect fuel pump timing, IMO, should not cause this failure. It would have to be SO wrong you would have difficulty in starting it, if at all, and, too far advanced and still able to run would most likely be so noisy you would hear it, and would probably break the top piston ring and not the valve.

I also find it interesting that #3 failed both times.

Incorrect "engine" timing could cause this but I would expect to see damage to the other valves from "0" clearance.
Even setting the valve clearance too tight would not cause this as it would have to be so far out of adjustment it would not start and, I think leaving an adjustment nut loose I think would most likely just back out to the point where the valve would not open at all.

You are most likely going to have to buy a liner to replace the one that is scored. Once they have been installed they are pretty difficult to remove without damaging them and "re using" them from one install to the other is not really a good idea anyway. They are a dry liner and there is a special pressing/pulling type of tool/procedure required to get them out. They can be put in by heating the block and freezing the liner but as mentioned above not really recommended.

Just doing a bit more thinking here.
What kind of shape is the crankshaft in, especially as it related to #3. Are the bearings pounded out, perhaps allowing the piston to come too far up in it's stroke and then hitting the valve ?
Perhaps pull the rest of it apart and see what that uncovers.

Paul

I will have to ponder this a bit more, but those are my thoughts for now.

EDIT:

Just looking at your photos again and, to me at least, does not look like there is a lot of oil lying around on the top of the head. It should, IMO, have quite a bit more lying there than what I see. Did you wipe it down at all, or is that just the way it came off ?

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Post Number:#3  PostPosted: Thu Mar 23, 2017 1:28 pm 
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Could bad injection timing or a faulty pump not cause EGTs high enough and/or carbon buildup to cause the valve to fail there, or is that only with forced induction? If there was a collision I would have expected the stem to be bent.

The engine had been sitting around for a couple months since failure, and the head had sat upside-down for a while too. I had verified that there was at least a couple drops per second of oil flowing at each rocker arm at idle previously. Wouldn't lack of oil be more likely to cause spring, retainer, rockerarm or pushrod failure anyway?

Do you think it would be worth it to get a bore gauge to check the other three cylinders and replace them, too?


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Post Number:#4  PostPosted: Fri Mar 24, 2017 6:06 am 
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I know that on my engine if I were to take the valve cover off that its nearly full along the edges where the cover gasket surface is. I'm wondering if there was not enough oil getting up there.

I also wonder how worn out the valve guides are ?
If the guides are worn excessively that may cause the valve(s) to wobble in the guide.
Perhaps pull the other retainers off and check to see for excessive guide wear ? Wobbling valves can break their heads off after a while.

I'm pretty sure that on this site somewhere someone ran into an issue with a replacement head not being drilled exactly the same as the one they took off and they had an oiling problem to the top end.
There were head gasket discrepancies as well.
I'm going by my memory on this which, aint really what it used to be, but I will spend some time on here and see if I can find the posting I am thinking about.

I could be wrong on this but it appears (to me at least) that the head you show is pretty "dry" and appears to have been pretty warm to get all that black crusty carbon there. As stated above, when I do a valve set on my truck ( which has been a while) that I end up with some oil running down the sides of the head making a mess.

Have you checked the rocker shaft for excessive wear on it and for "side to side" wobble in the rockers themselves ?

Another possible problem is the valve seat is worn out and not allowing the valve to sit flush and on center. This can cause it to wobble as well.

From the looks of combustion area of the head you show the EGT's do not seem to have been excessive to me.
You are correct in that excessive EGT's are more likely to occur with boosted engines, but you can still get these little guys pretty warm by adding more fuel.
Too advanced on the timing would make for a noisy "nailing" sound and you would really notice it. If the pump is mechanically timed to the engine correctly, ie the marks are correct, and, you say you were lined up with the scribe mark on the cover, then you can only more it a couple of degrees one way or the other.
If you were out a tooth on the mechanical engine timing I doubt you would even get it to start, they are pretty finicky that way. You can certainly pull the cover off and have a quick look as it's pretty easy to see.

I'm also looking at the area between #2 and #3 on your picture and it almost appears that they may have been leaking into each other. Both combustion areas seem to be really clean as well and I am wondering if you did not have a bit of water intrusion into them.
Were you having to add coolant ?

I will be interesting in what you find as you perform more of the autopsy.

I will see if I can find that thread about the oiling problem and who had it etc.

If it were me, at this point, I would pull it completely apart and see what kind of shape the crankshaft is in as well the camshaft.
You will get an better idea at that time if you are going to mess with new liners and finding a replacement head etc.

You can spend a lot of time and money on finding and purchasing engine parts for these little guys, and then there is the fuel system you would most likely have to deal with. Perhaps injector rebuilds and perhaps a pump overhaul.

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Post Number:#5  PostPosted: Fri Mar 24, 2017 5:29 pm 
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If you floor one of these engines for an extended period of time on a slight upgrade your EGTs will get over 1400 degrees without a turbocharger, I put an EGT gauge in my non-turbocharged SD25 engine just to see what kind of EGT temps they ran, I was very surprised to see how hot they get in even a minute floored going up hill on the hiway.
I did all this because I do have a turbocharged SD25 engine that was running very high EGTs on level ground on the hiway, and I wanted to find out what normal was, it was higher than I thought it would be, I figured out my issues and now normally am below 800 degrees on level ground, and get to 1200 degrees on hiway upgrades at the 70mph hiway speed limit, if I am trying to go 80mph then I have to watch the EGTs on hills, it's not that hard to get the EGTs up there, fact is it is easier for me to get the non-turbocharged engine hotter than the turbocharged engine as I am always closer to floored in that truck than I am in the turbocharged truck.
I hardly ever drive the naturally aspirated 521 kingcab truck anymore even though it is the coolest diesel truck I own, the turbocharged 720 is so much more pleasant to drive.

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Post Number:#6  PostPosted: Wed Apr 12, 2017 6:27 pm 
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Don't bother looking for the other thread about head oiling problems, that was me.

Rockers are fine, camshaft and crankshaft both appear fine. Never added coolant (I think the flash might be why it looks like that). I pulled a valve and there is a significant amount of play in the guide, but I don't really know how to properly check if it is in spec. Is there anything else I should check before I take it to the machinists'?

Also, does this look acceptable for a replacement piston? its a bit pitted, not sure if that would cause problems.


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File comment: donor piston
DSC_0402.JPG
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Post Number:#7  PostPosted: Thu Apr 13, 2017 4:32 am 
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Piston does not look too bad. I assume that you media blasted it with something to get it that color ? What kind of shape are the ring lands in? Hard to tell from the picture.
How does the liner look or are you going to get a new one ?
You say the rockers are fine, how about he rocker shaft ?

I am wondering if the lack of oiling in the top end might have allowed for a valve to hang open and get hit maybe ?
Might also be the cause of the worn out guides.
As for guide wear I will have to look in the FSM for a number. It's pretty small as I recall though.
I would take the oil pump apart as well and see how worn that is and how much tension is left in the pressure valve. If it's getting a bit weak either see if you can get replacement or find a washer to put under the spring to add a bit of pressure to it.

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Post Number:#8  PostPosted: Mon Apr 24, 2017 4:36 pm 
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plenzen wrote:
I am wondering if the lack of oiling in the top end might have allowed for a valve to hang open and get hit maybe ?


That was my first thought when I saw that clean break...

N_R

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