Light Colored Smoke

[Hinomotoman]

I just overhauled my Mitsubishi K3M. When the engine is put under load, it pours light colored smoke. It's hard to tell if it's white, blue or a combination. I have 450 lbs. compression on all 3 cylinders. No coolant/oil cross contamination. I did coat the cylinders with 50W motor oil when assembling. It has new pistons, rings and was machined to match the new pistons. The engine has been run about an hour since overhaul. Could this be the oil burning off the cylinders after 1 hour of running? Any ideas?

Eugene

 

[Ilikeurtractor]

Is it possible you could post of video of this? A lot of times smoke analysis can be difficult. It depends on the amount of smoke, engine temp, and even the background you look at the smoke against among a lot of other things. Dark backgrounds will almost always show some white smoke especially on engines not up to "working" temp. Most, if not all of this is water vapor from the combustion process condensing on the way out of the stack and should not cause concern. I wouldn't think there would be any of the 50W oil left on the cylinders that you used for assembly after an hour of run time.

 

[Hinomotoman]

It doesn't smoke unless I'm going up a steep hill or the engine bogs down for some other reason. You can't see through it. It's that thick. If the tractor is sitting still and you run up the RPM's, it doesn't smoke. I have no way of posting a video but it's thick enough to embarrass me in front of the neighbors.

Eugene

 

[Ilikeurtractor]

Would you call it more gray or white?

 

[Hinomotoman]

It's really hard to tell , it's very close to both. If it's grey, it's a very light grey.

Eugene

 

[Ilikeurtractor]

Not really sure what to tell you since your compression is good for each cylinder and we are assuming no coolant getting into the cylinders. Was the smoke purely black before under the same circumstances? Supposedly stuck rings could cause white smoke but I think that should show up in low compression. Maybe even air in the fuel lines but I don't have personal experience with either of those. Bleed the fuel lines one more time to the pump. Other than that I'm thinking I'd run it in some more and keep an eye on it. How does power feel when it's doing this?

 

[aczlan]

Can you do a leakdown test?

Aaron Z

 

[houstonscott]

You might have some oil getting by rings until they seat. Keep rpm's low, don't stay at same rpm for more then 15 minutes. Very speed. Keep loads light for as many hours as you can tolerate. Let those rings seat. Don't put it under heavy loads for 50 hrs. HS

 

[Hinomotoman]

Not really sure what to tell you since your compression is good for each cylinder and we are assuming no coolant getting into the cylinders. Was the smoke purely black before under the same circumstances? Supposedly stuck rings could cause white smoke but I think that should show up in low compression. Maybe even air in the fuel lines but I don't have personal experience with either of those. Bleed the fuel lines one more time to the pump. Other than that I'm thinking I'd run it in some more and keep an eye on it. How does power feel when it's doing this?

I don't know how the engine acted before. I bought it not running knowing it needed an overhaul. It has plenty of power at all stages. The air in the lines might be something to check into. I bled it up to the injection pump and hit the starter to bleed injector lines and it started. It starts in 40 degree weather without the glow plugs.

 

[Hinomotoman]

Can you do a leakdown test?

Aaron Z

I don't have the gauges for it but I will get some. What will that show me?

 

[Hinomotoman]

You might have some oil getting by rings until they seat. Keep rpm's low, don't stay at same rpm for more then 15 minutes. Very speed. Keep loads light for as many hours as you can tolerate. Let those rings seat. Don't put it under heavy loads for 50 hrs. HS

Will try that. Thanks

 

[Ilikeurtractor]

Late timing can cause white smoke also. This can be either pump timing or cam timing (which is usually tied to pump timing). Not knowing what the previous owner had apart could make this challenging.

 

[Kernopelli]

Just rebuilt my K3F and assembled it with regular 30W. No smoke whatsoever under any engine speed or load. In this same engine I once had to replace the #3 rod and I put new rings in with it at that time just as good measure since I had it apart ( hydrolocked the engine in pond accident and bent the rod). I didn't crosshatch the cylinder wall that time and it took about 5 hrs of running time before the new rings finally seated. It had light white/bluish smoke until they seated......just like it smoked prior to putting the new rod in. I was very concerned that the rod or rings were not right, that I still had a some water/moisture in the engine etc. but in the end I am sure it was just an issue of the rings on #3 seating. Ran great with no smoke for the next 5 years/600 hrs until a rod bearing spun ( very thick oil, partially obstructed pickup screen on a cold morning start up was the culprit there).

I'm curious, did you put a fresh bore or finish/deglaze/ crosshatch the cylinders on this rebuild? If not, my experience is that it will take a good while for those new rings to seat.

 

[houstonscott]

Should have set all the timing on rebuild.

HS

 

[Hinomotoman]

Late timing can cause white smoke also. This can be either pump timing or cam timing (which is usually tied to pump timing). Not knowing what the previous owner had apart could make this challenging.

The previous owner didn't have the engine apart. I took it apart. I put the pump shims back just like they came out. It starts way too easy to be out of time.

 

[Hinomotoman]

Just rebuilt my K3F and assembled it with regular 30W. No smoke whatsoever under any engine speed or load. In this same engine I once had to replace the #3 rod and I put new rings in with it at that time just as good measure since I had it apart ( hydrolocked the engine in pond accident and bent the rod). I didn't crosshatch the cylinder wall that time and it took about 5 hrs of running time before the new rings finally seated. It had light white/bluish smoke until they seated......just like it smoked prior to putting the new rod in. I was very concerned that the rod or rings were not right, that I still had a some water/moisture in the engine etc. but in the end I am sure it was just an issue of the rings on #3 seating. Ran great with no smoke for the next 5 years/600 hrs until a rod bearing spun ( very thick oil, partially obstructed pickup screen on a cold morning start up was the culprit there).

I'm curious, did you put a fresh bore or finish/deglaze/ crosshatch the cylinders on this rebuild? If not, my experience is that it will take a good while for those new rings to seat.

The previous owner ran it without an air filter. I had to have it bored 40 thousanths and replaced pistons. It was crosshatched. I spent $2500 on parts alone not including machining costs with also included rebuilding head. Maybe I need to give it more time but it seems really excessive to me and I would think with 450 lbs. of compression, the rings would be seated.

 

[houstonscott]

Does it use oil? The value guides may leak oil into combustion chamber, unless they were replaced.

HS

 

[Hinomotoman]

Everything internal was replaced. I haven't run it long enough yet to tell about any oil consumption. The oil is still clear. The reason I did a compression check is that I thought because of the smoke, the gaps in the rings might have become aligned. But apparently that's not the case.

Eugene

 

[Kernopelli]

Coolant leaking into combustion chamber and "burning off" or a fuel issue? ( I assume it is fresh fuel and the tractor has a water separator/sediment bowl), injectors not giving good/full spray? Leak down should show if it's a coolant issue. You could pull the injectors individually and visually inspect the spray pattern.....don't know how effective that really is in all scenarios of injector delivery issues though?

After my rebuild, I started the engine on the 18 month old fuel that was in the full tank stored indoors. It initially ran horribly....it didn't smoke but it sputtered, rev'ed slow and was hard starting. I was devastated! I changed the fuel and she ran like a top immediately. I have heard numerous stories about diesel lasting years but in this instance, 18 months made the difference between tractor fuel and brush pile starter.

 

[Hinomotoman]

Today I bled the fuel system again. No air at all. When I loosen the injector tubes it slows down on all 3 cylinders so I know it's firing. I haven't started it since Saturday. It still starts immediately without glow plugs. I moved the throttle the full range several times. No smoke until I load the engine. There is no power loss. I'm stumped.