Question for you engine builders--- Kind of long

I've been building engines, or all types, for more than 20 years, and have run up on a problem I can't figure out, nor can anyone of the multitude of people I know (many of whom have build engines longer than I have) can figure out either.

I had a N844T Shibaura brought to me that was pumping raw oil out the exhaust, after supposedly being rebuilt. My first thought was the turbo. It had some wear, and I could tell it had never been off, so I had it rebuilt. The problem seemed to get worse.

So I opened the engine up. I saw nothing that jumped out at me that would cause the problem, other than that the supposed 'rebuilder' had lied to the owner, and had not rebuilt the engine as he said he did. This was apparent in the old pistons, worn bearings, etc.

So, everything went to the engine machine shop, and came back to me with a refreshed head (valves and guides seated, but not replaced as they were within wear specs), bores still within standard spec, but honed and crosshatched, etc, etc. In other words, it was done right.

Built the engine using all new parts. Test ran, and it began spitting raw oil out the exhaust again. Given that the internals were new, I had the turbo rebuilder check it again. They found nothing wrong. I then set up and ran the engine without the turbo, and it was still spitting oil out the exhaust on #2 and #4. The oil appeared to be coming from around the valve stems.

So, checked compression, and it was good all around being in excess of 410 psi just by turning it with the starter. So I pulled the head. No indication of oil being burned on top of the pistons, and only a small dark spot where the injector fires on each one.

Pulled the valves, and as the shop had told me they were worn, but still less than half of spec toward the limit. Took the head back and had it completely done. They had to machine it to put in replaceable guides (which it didn't origionally have), but it came back to me this time all new.

Got the engine together last night far enough to do another compression check. Again I got 410 -420 on all 4 cylinders. I finished it up this morning and test ran it. Within a couple of minutes, it was slobbering oil out of the exhaust again.

This time when I pulled the manifold, not only were #2 and #4 wet, but #1 was wet, and #3 was getting there. Funny thing though, on #1 and #2 valve stems were soaked in oil, #3 had some on it, but not as much, and #4 was dry as a bone.

Now I'm at the point of looking for any ideas of what could be happening as I have covered everything I can think of along with everything anyone I have been able to find has thrown out to me.

If there was ring wear, or the rings weren't seating, I could understand blowby causing oil to get pushed into the cylinder on an intake stroke, but there is no indication of blowby, and with 410 plus pounds of compression, it's obvious the rings have seated. Nor do I see any indication of it being an oil control ring issue. If that was the case, why was #1 dry as a bone when I pulled the head the first time, but the second time now, it's wet after having the head completely worked, and the pistons not having been removed?

Like I said, I've covered all scenerios me, and about a dozen others have thought of, and eliminated all of them by testing. Mind you I have done far more than I've stated, but getting further into details on what all has been done would take three times this amount of writing.

That said, do any of you guys have any ideas, because I and many others I know, are out of them on this problem?????????????

Is the head gasket is OEM. Friend did a 1700 Ford a few years ago and had a coolant smell in the exhaust .Improper fit head gasket from Oriellys. Went to the NH dealer and bought a OEM. End of problem.

Good luck.

How does the oil get to the head? Probably up through an internal passage? If it was external, I would cap it off and run it, to see if there's some crazy leakage/crack in the head.
These situations are terrible. Everybody loses.

just finished a 3910 ford doing same thing had head gone through at machine shop valve seals where bad but guy put new valves seats guides and seals in the head and fixed it

I would check the head gasket. I rebuilt one years ago. Oil out the exhaust. Turned out the oil drain part of the gasket was not cut right. Oil was backing up had to go somewhere.

Any cracks or leaks in the oil galleries?

Could there be a little orfice missing that limits the flow of oil to the rocker arms?

boy do I feel for you,..had a ford v-8 in a truck that had great oil pressure cold but hardly any when warm, never did figure that one out even after machine shop rebuild

Oil pump relief valve not relieving?

Drill 1/8th inch hole in the valve cover as low as you can while still leaving room for a screw head. Start it and if oil runs out, it is flooding the head. the drain might be blocked, or the wrong head might be on it, or wrong gasket. Jim

Wayne ,How was the piston ring and clearance,You didn't say if the pistons were replaced or not.I have seen worn piston ring lands cause that problem and they still had good compression.

When you pulled the turbo the first time,was oil coming out the exhaust manifold then?And going into the turbo?
My first thought after you running it without the turbo,is oil laying in the valve cover,and not returning to the pan.Can you see the intakes thru the exhaust ports-are they oil soaked?But since the problem occurred before any work was done-why did the first 'rebuild' happen,or were they even into the engine at all-it seems like over oiling to the top end,or not returning.Is this an over head cam engine?Maybe oil leaking from an oil passage/bearing? Maybe oil return blocked-pour clean oil down it and see if it goes to the pan or backs up?Can you run it without the valve cover,I know it's messy,but maybe lay a heavy towel over it,and lift it up and peak.I don't know what all you have tried,but these are a few ideas maybe you can try.
Is this a huei engine-can oil pass thru the injectors,I don't think so-if it is,how are the injector o'rings?Let us know what you find,Mark.

Wayne
Call me tomorrow sometime.

Had a 3000 ford doing the same way.Rebuilt engine appeared to be still be throwing out oil.Turns out muffler was full off oil.
You can try a straight pipe to check it out. It took a long time to burn the oil out of the muffler.

Hello NCWayne,

My guess is in the head, or the head gasket has some "0" ring mjssing? Take enough oil out of the engine to fill the top of the head and see if it drains properly. Easy test to do. With that kind of compression it is a diesel. Oil may be going by the injectors seals? I really think tbat the head needs a HARD look. Pressurized everyway that its possible, that was my first thought. Having a different prospective on here may help you,

Guido.

Is it possible the oil is not draining from on top of the head,flooding the valves and guides?

I would bet that the oil is not draining from the cylinder head correctly. Remove the valve cover and inspect the oil drain passages. I have seen them blocked by junk and or the wrong head gaskets. Also some motors have an orifice in the oil supply to the rocker arms. IF this is left out there will be too much oil pumped into the top of the motor.

I have never touched a Shibaura motor. So I am not able to give you a hands on opinion. Your getting oil from the cylinder head. Either from around the valves if the top is not draining correctly or from an internal problem with the cylinder head. Could this engine have been over heated before the first guy messed with it??? I have seen Cummins big block motors have internal cylinder head cracks that will leak oil into the exhaust side of the head. It usually was a crack around the exhaust valve area. So they will blow oil out the turbo/exhaust but not have oil in the cylinders.

Good comments in this thread.

Is the crankcase properly vented? Any chance you're getting pressure in the lower end and interfering with oil ring function?

Have seen oil burning tractors where the problem was a crankcase vent tube clogged by mud dauber nests. With the vent cleared the oil burning magically went away.

I going to go with CenTex, and check the breather. Friend had a Cat skidloader and the thing started pushing oil out the exhaust. Dealer had it twice, I looked at it some, even took the breather apart, they replaced three turbos, looked like it was the problem, then dealer researched and found a service letter that the diaphragm type breather had a pinhole causing this. Two years and no problems, was a perkapillar engine, perkins/cat.

No oil passages in head other than return ports. They are clear, and flowing so there is no flooding on the top end. In fact I can look down through the fill spout and see the rocker arms when running. This verifies the lack of flooding, as well as negates any chance of it being pressure in the crankcase as it creates about an 1 1/2 diameter direct vent, on top of the 3/4 vent tube.

Not to mention when I test ran it without the turbo last time, the turbo return was open, and it dumps directly into the side of the block, inches above the oil level, and I had nothing coming out of it either.

The oil line to the rocker shaft is external, and the rocker shaft rides in an aluminum housing that is bolted to the top of the head. That being the case, the only passages between the head and the block are water.

There is no smoke, just liquid oil more or less oozing from the exhaust from the turbo. I do not have the muffler on it. hen I had it running the first time I had burned the muffler out, so it was dry. It took maybe 20 minutes of hard running before I started seeing oil coming out of it. This time I figure it would be about the same were I to install the muffler.

I can't remember all of the suggestions/questions thus far, but suffice it to say I have covered every one of them thus far. Even so, I'm still looking for suggestions, no matter how uncommon, or unconventional they may be.

It's been over thirty years since I was inside a diesel, but here are a few thoughts:

1. It should be nearly impossible for oil to leak pass the valve guides on a turbocharged engine, since both intake and exhaust ports have positive pressure most of the time, and oil under the valve cover shouldn't have any pressure. The only way oil is going to make it into the exhaust is if it's under pressure.

2. Is your customer ABSOLUTELY CERTAIN the oil problem didn't exist before the first "rebuilder" went into it? That's important! If it was OK before it was worked on, then the first guy put it back together wrong and you just repeated his mistake. But if it was already blowing oil when he took it in, then something broke inside the engine and neither of you have found it.

3. Do you know exactly what, if anything, the first guy touched in the engine? Were injectors pulled? Sleeves pulled?

There were some issues with the crankcase breathers on some of those engines, but I think the problems were on the 2.2 liter newer engines.
This isn't residual oil in the muffler from prior to the rebuild? This is fresh oil?

Only other things I can think of is excess rod side clearance and piston cooling jets.

Does this engine have piston cooling jets that spray oil at the bottom of the piston? Missing restrictors or nozzles on these?

Is there a plug in the end of the camshaft. Had a small Kubota small diesel that did
this after we had it apart. The plug was missing out of the end of the cam and it was flooding
the head somehow. We put the plug in and the problem went away.

After reading your 2nd post,and you say it is not flooding the head,then I would look at the pressure side of the oil feed.I would pressurize the oil inlet on that external line,and I would remove the exhaust manifold and observe-maybe even remove the intake too and observe your ports. And maybe back off the valve adjustment so all valves are closed.I doubt it is valve seals or rings.And is it a huei engine-oil pressure fired injectors? Something is wrong with the head,for sure.Mark

Also when I pressurized the oil passage,I would have the valve cover off.From what you have said it is probably a common rail fuel system,but I wondered about if it was a huei system because there is a lot of oil pressure involved on those.Mark

I haven't read thru whole post yet,
Look for cracked piston.
Make sure oil ring is installed correctly.
I've seen rings test good psi and when taken apart, I can stretch n bend the rings in a straight line.
If oil rings are in upside down, the oil will stay in top of cyl vs being scraped downward.

Had a quick look online at a manual for this engine and came across the following;

MODELS E673L, S773L, N844L, N844L-T ONLY Add engine oil slowly. Pouring the oil too quickly can result in the oil overflowing into the air breather valve and then into the air intake manifold. Cranking the engine with oil in the manifold will severely damage the engine.

Is there a possibility the breather valve mentioned is missing or sticking?
Or maybe a baffle is missing.

The manual also stresses over and over to not overfill the oil.

I worked on a 6.2 diesel that had an oil issue and ended up connecting an external pump to the oiling system and pumped solvent through it with the engine not running and partially dismantled to locate the leak, in that case it was pushing oil into the coolant through a crack/flaw in the block.

on some of the heads.. the valve spring landings are cut down, into the head, so that they are lower and designed to hold oil around the valves. this is so that when not run for 6 months or more, the valves will not rust or stick. this design on some of the ford tractors also means that the exhaust valves will feed some oil... into the exhaust.

Absolutely perfect valve guides, valve stems, and new stem seals will help, but not stop it 100%. As its called slobbing, many fords will do this when run lightly, and then clean up when warmed up and put under a load.


First off, are your valves recessed into a well or sunken into the heads... its there any play what so ever in the valves in the guides? Lots of machine shops would knule the guides but this is not a good fix. did it get new seals, and are the seals staying seated on the head valve stem boss, or are they moving up and down on the stem and doing no good what-so-ever?

On the turbo... turbos only have a couple of washers on the shafts for oil seals as anything else will burn up from the heat.. Therefore.. the drain MUST BE straight down, and must have NO restriction to oil drain what-so-ever. lots of drains cake up and the size of the passage is narrowed, causing oil to back up on the turbo shaft and then it will start feeding oil... REMOVE the drain line and rod it out to make sure it is 100% open with no build up. Drain lines are oversized to prevent any oil from backing up, but cheaper oils will cake up due to turbo heat and slowly clog the line over the years.

good luck on the project.

If there was ring wear, or the rings weren't seating, I could understand blowby causing oil to get pushed into the cylinder on an intake stroke, but there is no indication of blowby, and with 410 plus pounds of compression, it's obvious the rings have seated. Nor do I see any indication of it being an oil control ring issue. If that was the case, why was #1 dry as a bone when I pulled the head the first time, but the second time now, it's wet after having the head completely worked, and the pistons not having been removed?

You have an oil ring problem, without oil control you will never get the rings to seat resulting in the slobbering you see.
Engine will still make compression but the rings are not seated.

Hello NCWayne,

I just thought of something. On Cummins engines there is a passage hole that allows intake air to go through the rocker assy., and in the engine top cover. On turbocharged engines that hole MUST be plugged as too much pressure will pressurize the crankcase. I guess you have already checked crankcase pressure?

Guido.

Any chance the oil is coming in with the fuel ? Sometimes on a weak engine, guys will pour all manner of stuff in there to try and help it, including oils.

Did you ever figure out what went wrong with the N844t? Mine just sucked & burned 1.5 gallons of oil in 20 working hours, overheated and now is smoking awful and has a bad tick. This particular engine has always had cooling issues since we bought it from a rebuilder a couple of years ago. The first engine the guy sent us had a constant ticking noise that turned out to be broken rings on one of the cylinders. I'm guessing it has happened again. Funny thing is the computer never indicated an overheat condition. :roll: