Rebuilt diesel blue smoke and rattle only sometimes

[clinter36]

Hello all,

A few months ago I started a thread on a Shibaura / Perkins diesel that I was rebuilding. The rebuild went fine, I ended up having the machine shop bore the cylinders .020 over (for those that were watching that thread), rebuild the head, and polish the crank. Everything checked out and measured great.

The engine is a Shibaura N844LT in a Case skid steer.

All said and done, the engine got new pistons/rings/pins/etc, all the crank/rod bearings, cam bearings, 2 new pushrods, new oil pump, obviously all the gaskets and rebuilt injectors. I cleaned up the turbo, there was a tiny play but otherwise seemed fine.

Everything went back together fine. I filled her up with break in diesel and ran her per break-in recommendations. I now have about 13 hours on the machine mostly moving logs around with a grapple and it has run perfectly until yesterday. I do have an oil leak from the front timing cover I believe, I have to pull the radiator etc to get to that so I haven't tackled it yet.

Yesterday, I had run the machine for about an hour at mid throttle, probably around 1800 rpm, and it suddenly started smoking blue smoke. I believe the rpms dropped a little at the same time and I noticed a rattle or tapping. I pulled back on the throttle and brought it down to an idle where it continued to smoke and run a bit rough and rattle so I shut it down. I inspected under the hood and checked the oil and did not notice any issues. I needed to get it back to the house, so I started it back up and it ran perfectly fine no smoke, no rattle. I ran her back to the house and had lunch and let her cool. I then went and ran her again for about 45 minutes with no issues, I shut it off to do a couple things for 30 min or so, started it up and it was fine for about 5 minutes and the smoke and rattle started again. So I shut it off for about 20 seconds then started it and it was fine. I was finishing up anyway so I brought it back to the house. It did this one more time moving a rock later in the day, quick shut down and restart and it was fine.

Any ideas on what the heck could cause a diesel to burn oil and then after a restart suddenly stop ? My first thought would be the turbo, but the rattle does not make much sense. The rattle almost sounds like a valve sticking, but I don't see how that would cause the oil burn.

I think I am going to pull the radiator and investigate the oil leak today. Thanks for the help!

 

[dodge man]

Is it’s possible it’s fuel and not oil? It could be fuel and the rattle is a bad injector.

 

[clinter36]

Anything is possible, but the smoke is clearly blue.

 

[Ortimber]

My recommendation is to check the fuel system out. Bad injectors and/or worn injection pumps can cause the issues you are describing.

 

[number two]

Agree with above.
Since you installed rebuilt fuel injectors,one of them could very be not very well rebuilt.
Good Luck!

 

[clinter36]

OK, I won't rule it out. But since the smoke is definitely blue and I am not sure about the ON/OFF nature of a bad injector. Can we brainstorm a minute on ways that it could burn engine oil ?

Could be getting past the rings... maybe stuck rings
Could be getting down a valve guide seal
could be getting in the turbo

Am I missing anything.. ? Its a tier 2 engine so I don't think there is any way to connect the crank case vent to the intake. The valve cover simply vents down the side - so I don't think there is a potential issue there.

its got to be a valve guide / seal.

 

[IH3444]

Did you pay close attention as to how you properly arranged the compression rings on the pistons before installing. If two top rings are aligned with their gaps not 180 degrees offset it can allow oil to get from the crankcase to the upper combustion chamber easier.

 

[dodge man]

What lead me to something other than oil burning is the rattle, but I agree blue smoke normally means oil.

So many potential things. Rings, leaking head gasket from incorrect installation torquing , valve seals/guides, bores out of round etc.

My experience, but with gas engines, if it valve guides and seals, they smoke on start up and then clear up. I think this would hold true on diesels. They don’t leak much when running but after shutdown they slowly drain oil from the head into the cylinders.

 

[IH3444]

Very good point Dodge Man, new valve stem seals, as well as a properly rebuilt cylinder head with new guides if needed.

 

[clinter36]

Yes I was very careful with the piston rings - both right side up and the alignment of the gaps. Interestingly I was working off of two different service manuals for the engine and they both had different arrangements on the ring gaps, I went with 120 degree for the gaps and no gaps directly in line or 90 to the pin.

I put a call into the machine shop that did the head, block and crank work. I don't get long detailed responses, but he is very knowledgeable, he said his first thought was the turbo. He also said it would not be a major mechanical engine component, rings, valves, etc. Those things don't come and go... they break and that's that.

And agreed about the valves leaking... it tends to be on startup. I have a forklift that does exactly that.

I wonder if the turbo bypass is flapping or sticking or something.