Kubota 3 Cylinder smoking Bent Rod

Got a nice mystery here. Brought in a machine with heavy white smoke issue. Checked all the basics, then checked compression, valve lash and then a leak down test. One of the cylinders was almost 100psi less then the rest on compression. Put some oil in the cylinder tried again, put a little more oil, then a little more oil and it finally came up to spec. I was also getting leak by into the base. Pulled the head, turned the motor over. Cylinder walls looked good. Looking more closely cylinder in question wasnt as high as the other cylinders a TDC. Well of course to pull the oil pan you have to pull most of the machine apart to get the engine out to pull the pan. A few swears later the engine and piston was out. Well the connecting rod was bent in two directions. front to back and side to side. The piston was cocked and likely leaking past the rings because of that. First time I've seen this in a kubota engine. These 3 cylinders are in alot of equipment I work on and this is a first for me. What gets better is this machine has less then 200 hours.

So Leaky Injector? Waiting to hear back from Kubota before we spend any more time on this one. Warranty has my hands a little tied.

You don't give too many details about the installation of the engine but is there any possibility that it could have got water (or even snow, not sure how your weather has been) down the exhaust that has hydraulic-locked that cylinder the first time the engine was started afterwards..?

Did the white smoke issue start suddenly or has it been getting worse over time..? If it has been slowly getting worse then your thoughts of a leaky injector could well be right. I don't suppose you kept the engine oil you drained before removing the pan..? Does it smell of fuel..?

This is a brand new piece of equipment. The exhaust pipe is a foot lower then the head and the pipe is horizontal. So snow or water would be nearly impossible to get into the cylinder that way. Its a customer unit so maybe it got dunked in a pond for all I know. I saved an oil sample and when draining held a magnet in the flowing oil. Oil level in engine was normal, no smell of fuel or coolant. Nothing was found on the magnet. The piece of equipment started smoking and was brought into the dealer I work for. As far as I know it was sudden. Now it dawned on me this morning that it could have bent the rod and still ran normal until the piston wore enough to start loosing compression. The piston was tipped in the cylinder and the top edge was worn. So it may have still ran okay until the point the piston wore enough that it affected the rings to loose compression, at that point it may have started smoking.

What I need to check today is what I didnt think might be a key into the mystery. The carbon deposite on the cylinder wall above where the rings don't travel any higher on the cylinder wall is thicker on the cylinder in question compared to the other two. There might be a mark higher where the rings were stopping before the rod bent. If there is a visible line under the carbon in the two normal cylinders then there should be one in the bad cylinder. If there isnt........it may be proof enough that it was bent at the factory. It might be a hail Mary pass but I will check when I get to work.

I like you footer note I can relate but I have to edit it a little

I'd love to see things from a engineers perspective but unfortunately....... I find it impossible to get my head that far up my a$$.

I apologize if your an engineer

ether meets kuboter...

I'd think ether as well. Had a mechanic tell me to never use ether on a Kubota because the clearances are so tight. Seems like if the rings are gone could allow for more carbon buildup because less complete combustion and exhaust. A lot of ether could possibly bend a rod too. What machine is this engine in and how cold has it been?

DIYDAVE said:

ether meets kuboter...

Click to expand...

That was my thoughts too as I was reading the original post and Nige's reply. I've only dealt with one Kubota engine, that was in a Bobcat Skid-steer. That one had pre-combustion chambers or what ever Kubota calls them. Talk about a cold blooded engine! It needed the glow plugs to fire up at 75º even with new pistons and everything.

I can see someone not familiar with the use of the glow plugs getting ticked off at it not starting and emptying a can of "run-or-blow" down the intake of that little engine even after the first cylinder fires. The result would be like taking a 20 lb.(9 kgs. for you metric people) sledge to the top of the piston.

If it is decided to repair this engine I would be checking the other two rods very close, paying close attention to center to center lengths compared to a new one. Also not a bad idea to have a shop test the nozzles just to rule out the chance it was a leaking injector

The Kubota's before about 1995 were indirect injection and required glow plugs for the initial start even if it was 75 deg's but that said are still a great long life reliable engine. The newer direct injection start easier. Glow plugs don't hurt anything, the biggest problem is getting it started when it's -30 even plugged in. My skid steer has a 400 watt block heater but could use another one for when it's really cold.

kshansen said:

That was my thoughts too as I was reading the original post and Nige's reply. I've only dealt with one Kubota engine, that was in a Bobcat Skid-steer. That one had pre-combustion chambers or what ever Kubota calls them. Talk about a cold blooded engine! It needed the glow plugs to fire up at 75º even with new pistons and everything.

I can see someone not familiar with the use of the glow plugs getting ticked off at it not starting and emptying a can of "run-or-blow" down the intake of that little engine even after the first cylinder fires. The result would be like taking a 20 lb.(9 kgs. for you metric people) sledge to the top of the piston.

Click to expand...

Welder Dave said:

The Kubota's before about 1995 were indirect injection and required glow plugs for the initial start even if it was 75 deg's but that said are still a great long life reliable engine. The newer direct injection start easier.

Click to expand...

I don't see that many Kubota engines, but until now I thought they were still the same basic cold blooded IDI they had always been.

Even the modern ones I have seen seemed to need 20 seconds or more of glow plugs to even fire, at any temperature. But if you heat them up good they start immediately so nothing really to complain about. I don't know if IDI is still an option or was before Tier 4 but it was with a lot of similar engines.

Never had to use ether on one for any reason.

Is the engine in question IDI or DI?

For what its worth one of the injectors was leaking the one in the problem cylinder. It leaks at 120psi. I pressurized them with a air line. Funny thing it wasn't leaking from the tip it was leaking above the tip at the seam.

either was my first guess too

These newer kubota engines seem to start a little better in the cold if your patient enough to wait for the glow plugs to cycle. When you turn the key to the first position the glow plug light goes on and 10 sec or so goes off then it starts easyish even at 10 degrees. The older ones seem to need a bit more and you have to turn the key backwards or forward right before start.

It has a pre cumbustion chamber so its indirect.

The price on a new motor is 2400 from kabota, thats the dealer price. So its a waist of time and money to rebuild correctly. To do it right and warranty the work the crank wold have to be machined it was scored, All rods and pistons checked and or replaced. new injectors, head gasket, Head sent out to be checked. clean and assemble........by that time money and labor wise....why bother? These engines are throw away. Now if kuboata wont warranty it and it was me I would only replace the rod and the one leaky injector and run it. What do you have to loose?......and save up for a new motor.

I wonder if there is a way to test for either use CSI style????? The Carbon build up in the cylinders would have to have either in them in some form.......

Wekler Dave dont you mean the older kubotas were direct injection? Most of the newer motors are indirect meaning they have a pre combustion chamber.

Midnightmoon said:

Now if kuboata wont warranty it and it was me I would only replace the rod and the one leaky injector and run it. What do you have to loose?......and save up for a new motor.
...

Click to expand...

Sure is a shame that an engine that is probably only had a hand full of oil changes is going to end up in the scrap. I agree if it was mine and I was doing the work myself One rod, one rebuilt injector, a quick polish by hand of the crank, depending on damage to piston maybe replace that and a few gaskets and it would be back to work. And if it still ran good after a few days hard working I'd take the money saved and put it into the beer fund!

Midnightmoon said:

For what its worth one of the injectors was leaking the one in the problem cylinder. It leaks at 120psi. I pressurized them with a air line. Funny thing it wasn't leaking from the tip it was leaking above the tip at the seam.

either was my first guess too...

Click to expand...

Are you suggesting that the ether made the injector leak? It seems to me that if an injector was leaking in the cylinder that had a bent rod, Kubota should pay for it unless the owner admits he used ether.
I have only owned one Kubota and agree that they are throw away engines. They make sleeves for them that require boring after installation. What a joke. I understand that there are many happy Kubota buyers who have gotten 6,000 hours out their of engines, but it only takes one very minor glitch to derail the long life of a poorly engineered engine, and a bad injector is enough.

Midnightmoon said:

Wekler Dave dont you mean the older kubotas were direct injection? Most of the newer motors are indirect meaning they have a pre combustion chamber.

Click to expand...

I think you're confused. Most newer engines are direct injection. They start easier and are more fuel efficient. Perkins, Cat and Kubota all went away from indirect injection. I find it a little hard to believe a new 3 cylinder Kubota diesel is only $2400. The small engine drive welders with the Kubota diesel option are a lot more than $2400 difference. More like double that or more.

Four years ago I looked at a Carrier refrigeration unit on a trailer with a bad white smoking problem turned out that the owner used ether. Utility repaired it, very spendy to repair that Kubota.

Truck Shop

I've seen this happen when using an oil pump and metered fill nozzle and filling the engine oil through the valve cover. If I remember right it fills to quickly, fills the valve cover up and a small amount of oil runs through the rubber hose from the valve cover into the intake and then into one of the cylinders. This was on a brand new EXMARK mower that had the 100 hour service done. EXMARK had a bulletin out on the problem.

check said:

Are you suggesting that the ether made the injector leak? It seems to me that if an injector was leaking in the cylinder that had a bent rod, Kubota should pay for it unless the owner admits he used ether.
I have only owned one Kubota and agree that they are throw away engines. They make sleeves for them that require boring after installation. What a joke. I understand that there are many happy Kubota buyers who have gotten 6,000 hours out their of engines, but it only takes one very minor glitch to derail the long life of a poorly engineered engine, and a bad injector is enough.

Click to expand...

I know of welders with Kubota's that have gone 13 and 14,000 hours and never had a problem and these were rental units from Red-D-Arc. You can bore a Kubota and not need a sleeve. Kubota's were so popular in skid steers that Case came out with the 1838 to compete with all the other brands running Kubota's. Kubota didn't get to be the engine of choice in thousands of machines and the best selling compact tractors because they are poorly engineered.

There are Carrier refrigeration units with well over 20,000 hrs on them with zero issues. We've had over 150 trailers with Kubota powered units and the only odd issue was a leaking soft plug on one unit.
And a few leaking rear main seals on engines with 15,000 hrs. Never had the valve cover off or any fuel system problems on any of those engines-they just run.

Truck Shop

Welder Dave said:

You can bore a Kubota and not need a sleeve.

Click to expand...

The "throw away engine" issue, as I see it, is not whether an engine can be sleeved, but whether it can be in frame overhauled. If a block must be sent to a machine shop to restore cylinder compression, it must also be 100% stripped down. labor must be invested in removing and reinstalling the crankshaft, gear train, injection pump etc. which is a poison pill 80 to 90% of the time. That is what puts them in throw away category, even if they lasted 25,000 hours. The manufacturers know this and that is why I call it "throw away", like a Bic lighter. It is a malicious act of planned in obsolescence when a manufacturer makes sure their engine cannot be in framed. It is a deliberate design flaw done to increase their market share and ensure future profits.
Some throw away engines are very long lasting and good performing engines. Cummins and Cat makes them too. But they are still throw away engines.
As long as I can't in frame overhaul one I will call them what they are. Sorry.

Yeah this engine cant be frame rebuilt that really gets me going when you cant pull the oil pan. Now Im really hot that they did that on purpose.

This 3 cylinder is 2400 dealer price. I was told by the rep its 1000 for kubota. Retail price sure 5000. This isnt a tier 4 motor. Kubota must have slipped it through with credits. its a 2016 unit

These kubota engines are great we have almost no problems with them and we have 100's in our fleet.

Interesting on the oil fill location I will have to look into that.

The tier 4 engines are dirrect but before that are indirrect like the one Im working on.The glow plug in the pre combustion chamber would seem to me to start an engine easier then the direct inject but on the new high pressure tier 4 the fuel is so atomized dirrect would seem to light easier. Tier 4 perkins 404 is indierect but thats an old style engine with tier 4 bells. The perkins 854 is dirrect along with the new tier 4 kubota. Im not a engine historian just know what I work on. Cummins I work on are direct but there older I dont know about the newer tier 4. With sequential injection showing up now it makes sense they would be dirrect. I really dont know please teach me the pre 1995 engine were indirect but Im working on a 2016 thats indirect is that still a pre 1995?

As far as the bent rod who knows the force that bent the rod could have effected the injector or the injector could have caused the bend, or either, or oil filling through the valve cover? Thats all I have. One funny thing on cylinder #1 the injector line was tight on the injector but the injector was finger tight in the head. When I found that I thought I found the problem but that cylinder was fine.

Welder Dave said:

Kubota didn't get to be the engine of choice in thousands of machines and the best selling compact tractors because they are poorly engineered.

Click to expand...

Another point to ponder is whether there were better choices. Were there any other makes of diesel engines in the same class that could be in framed when these thousands of Kubotas were sold? I think all the manufacturers have taken up planned in obsolescence. I think these Kubotas sold because they were the lesser of evils.