Kubota engine failure. Please help

[manugoss]

I have a Kubota ''grey market'' L1-315 4 cylinder diesel and I have an engine problem. The engine model is a V1512. The engine ran out of coolant and ran until engine starting to show some sign of failure. I would like to assess the damage to know what I need to do to fix it but don't know where to start. For those of you that are wondering how can this happen, I bought the trator 5 years ago and the temp gage was not working but a few month ago, I installet an inline coolant heater. My father and I are using the tractor almost daily but yesterday I notice that the hose that connect to the block heater broke completely draining all the coolant fluid. I don't know if the tractor have been running for hours or days without coolant because it is still below freezing around here and the tractor is used in the woods with a winch so it is used almost 80% of time on idle.

So yesterday I was pulling a load up a hill when the tractor lacked power and stopped. Check the oil buy then I notice that there was no coolant left and that the heater was cold. Today I replaced the engine oil, added coolant and fixed the leak. I started the tractor. It starts pretty easily but it smokes alot more that usual and it lacks power. If you press on the pedal it will take more time than usual to rev up but will. There are no weird noises like valve ''click'' exept maybe a sort of on even idle. The smokes coming out of the exaust smells like unburned diesel. I also notice a tube on the side of the engine where smoke comes out and drips of black fluid similar to oil. This tube appears to be a vent of some king and it is pointing downwards. I do not have a compression tester.

I did some resarch online and it seems like not alot of information or parts are available for the V1512 engine. Provided the info above is it possible to know what could have happened? I was thinking of removing the engine top part to look for damaged gasket or cylinder scoring. Would it be better to start with a compression test? Any ideas or suggestion on where to start with this project. I am mechanically inclined althout I never work with 4 strokes engine before. I rebuilt many saws in the past and will be willing to learn on diesel engine with this project. Thanks for all your help.

 

[Industrial Toys]

That would be a good place to atart. Remove the head and inspect the cylinders. I hate to say it, but this accident will cost a bit. Diesel engine work and components are not known for being cheap. Fortunately you sound like you can do a lot of the work yourself.

I don't know why tractors don't for the modest price of of what it would cost have Murphy style shutdown gauges to kill the machine. This is a story that all those people that think PTO gensets are a good idea should read!

 

[GManBart]

The exhaust that smells like diesel fuel is an indication of "wet stacking" meaning unburned fuel is in the exhaust...it's carbon that turns the diesel black and makes it look like oil. You can tell it's not oil because of the way it stains things, and doesn't wipe off easily the way oil will. If the head gasket is cracked, or the head is warped/cracked (both very common for engines run without coolant) it won't be able to generate enough compression to fully burn the fuel, which would cause the loss of power and wet stacking. The drain tube could be related, or it could be seized/scored rings allowing fuel to get past the rings into the block, but it sort of depends on where the tube is located.

 

[joeblack5]

I would start with a compression test and also a leak down test to see if any of the valves are leaking. You probably will end up tearing the top off.
Your vent tube blowing smoke sounds like you have blow by. You can verify this by taking the oil filler cap of at idle and see if it blows or not.
That you smell diesel means incomplete combustion, if idles a little uneven then probably the compression is low on that cylinder. Besides the compression test you can try cracking the injector lines one by one . The one that does not lower the rpm is your damaged cylinder.
Scored cylinder, broken rings.


Good luck
Later J

 

[manugoss]

I would start with a compression test and also a leak down test to see if any of the valves are leaking. You probably will end up tearing the top off.
Your vent tube blowing smoke sounds like you have blow by. You can verify this by taking the oil filler cap of at idle and see if it blows or not.
That you smell diesel means incomplete combustion, if idles a little uneven then probably the compression is low on that cylinder. Besides the compression test you can try cracking the injector lines one by one . The one that does not lower the rpm is your damaged cylinder.
Scored cylinder, broken rings.


Good luck
Later J

I do not have a compression tester on hand. I think I will just remove the top part and verify the head/ cylinder without checking the compression. I did not have much time today but I did check for 2 out of 4 injectors (I check at the IP and my wrench is too big to check cylinder 2 and 3). For cylinder 1 and 4, the engine will run rough if I unscrew the fuel line. I took the oil filler out and the blow out continue to exaust some gases. I should have time this weekend to really dig into the diagnosis. All your comments are welcome and much appreciated. I will let you know how the project comes along. Thanks

 

[manugoss]

Today I removed the engine head and finally discovered what was wrong. The third piston partially melted on the cylinder walls. Exhaust port was wet with unburned diesel as opposed to3 other ones. I removed the piston and the rings were still in one piece. There is very ligh scoring on the cylinder walls but my nails will not even catch. The biggest issue is the aluminium from the piston that is now stuck on 2 spots on the upper cylinder part. My plan is to try to remove the aluminium and use the stone to lightly hone the cylinder in place. I would then throw a new oem piston witht new rings. The engine head seems in good shape but I will try to find a straight edge to check for flatness with filler gauges. Does anyone have a trick to remove the aluminium off the cylinder walls? I know that with chainsaw one can use muriatic acid with some Q-tip and some light stoch brite. Any thoughts on the plan of action above? Any help/ opinion is very appreciated. For those who wonder, this tractor is mostly used for light duty work 200h a year mostly rototiller in summer, and logging winch in winter. Cheers

 

[manugoss]

Today I removed the engine head and finally discovered what was wrong. The third piston partially melted on the cylinder walls. Exhaust port was wet with unburned diesel as opposed to3 other ones. I removed the piston and the rings were still in one piece. There is very ligh scoring on the cylinder walls but my nails will not even catch. The biggest issue is the aluminium from the piston that is now stuck on 2 spots on the upper cylinder part. My plan is to try to remove the aluminium and use the stone to lightly hone the cylinder in place. I would then throw a new oem piston witht new rings. The engine head seems in good shape but I will try to find a straight edge to check for flatness with filler gauges. Does anyone have a trick to remove the aluminium off the cylinder walls? I know that with chainsaw one can use muriatic acid with some Q-tip and some light stoch brite. Any thoughts on the plan of action above? Any help/ opinion is very appreciated. For those who wonder, this tractor is mostly used for light duty work 200h a year mostly rototiller in summer, and logging winch in winter. Cheers

Here is some pictures:

 

[Arc weld]

I wouldn't be surprised if the other cylinders/pistons show damage as well. I don't think a hone is going to fix that.

 

[Industrial Toys]

Sorry, I can't help. But it is most interesting to see what actually can happen in such an event. I'm guessing that all that stuff is critical to the thousands of an inch and you will probably end up taking it to an (engine) machine shop.

 

[Agvg]

Is there damage to the cylinder or just melted aluminum? It its just melted aluminum you can try the trick with acid to remove aluminum.