Sand Mountian
New member
- Joined
- Apr 24, 2022
- Messages
- 1
- Tractor
- Myhindra
What causes blue smoke from exhaust after tractor is used about 20/30 minutes ?
Blue smoke from exhaust
- Thread starter Sand Mountian
- Start date
Does it use oil?
Motor oil will cause blue smoke. You said it starts after the tractor warms up. As the oil warms it thins and may be able to make it past the piston rings if they are worn.
ROUSTABOUT
Elite Member
- Joined
- Jan 30, 2008
- Messages
- 3,186
- Location
- Luther Willis Hill, AR
- Tractor
- Pettibone, Ford, Massey Ferguson, International, JD, David Bradley, home mades
Is it royal blue and makes a cloud above machine?
Woodstock Walt
Silver Member
Not sure what model your Mahindra is, but that is a common occurrence with the DOC emissions system of the MCRD engines. Mine does it too.
The DOC (diesel oxidation catalyst) is contained within the exhaust system and acts similar to a catalytic converter on a gasoline car. The honeycomb design captures unburnt fuel and waste gasses, then heat from the exhaust reacts with the catalyst and burns off the waste (soot). However, heat is integral to the DOC's operation, and it must reach proper operating temperature before it begins to burn off the soot.
The blue smoke you're seeing is likely the soot that has accumulated while the tractor was warming up, being burnt off. This can also happen if the engine has been run for an extended period of time without much load on it. If the engine isn't working hard enough to produce hot exhaust gasses, the DOC will collect the waste instead of burning it off. Once you put the engine under a heavy load, the exhaust temps will rise, the DOC will reach operating temperature, and the accumulated soot will burn off causing a cloud of smoke to emit from the exhaust.
This is why many operators who run their machinery at low load/low rpm exclusively later have issues with emissions equipment. The soot just continues the build up until it turns to hard crud and plugs things up. A hot exhaust system is a clean exhaust system, and you've got to work your machinery hard sometimes to get it hot.
For example, I use the hydraulics of our 4540 to power our wood splitter. This doesn't put much of a load on the engine, and soot accumulates within the DOC. I used to notice that whenever I drove back up the steep hill from the woodlot, the tractor would emit blue/gray smoke for a short period of time until it seemed to "burn off". That's the DOC reaching operating temperature and burning off all of the soot it accumulated while chugging along powering the splitter (low load/low rpm).
Now whenever I finish splitting for the day, before I shut the tractor down I'll raise the throttle and curl the bucket until the hydraulics bypass, then hold the function for 15-20 seconds. This puts a load on the engine and raises the DOC's temp, burning off the accumulated soot and producing a cloud of blue/gray smoke. Once it clears up I'll idle down for a minute to let things cool, then shut down.
The DOC (diesel oxidation catalyst) is contained within the exhaust system and acts similar to a catalytic converter on a gasoline car. The honeycomb design captures unburnt fuel and waste gasses, then heat from the exhaust reacts with the catalyst and burns off the waste (soot). However, heat is integral to the DOC's operation, and it must reach proper operating temperature before it begins to burn off the soot.
The blue smoke you're seeing is likely the soot that has accumulated while the tractor was warming up, being burnt off. This can also happen if the engine has been run for an extended period of time without much load on it. If the engine isn't working hard enough to produce hot exhaust gasses, the DOC will collect the waste instead of burning it off. Once you put the engine under a heavy load, the exhaust temps will rise, the DOC will reach operating temperature, and the accumulated soot will burn off causing a cloud of smoke to emit from the exhaust.
This is why many operators who run their machinery at low load/low rpm exclusively later have issues with emissions equipment. The soot just continues the build up until it turns to hard crud and plugs things up. A hot exhaust system is a clean exhaust system, and you've got to work your machinery hard sometimes to get it hot.
For example, I use the hydraulics of our 4540 to power our wood splitter. This doesn't put much of a load on the engine, and soot accumulates within the DOC. I used to notice that whenever I drove back up the steep hill from the woodlot, the tractor would emit blue/gray smoke for a short period of time until it seemed to "burn off". That's the DOC reaching operating temperature and burning off all of the soot it accumulated while chugging along powering the splitter (low load/low rpm).
Now whenever I finish splitting for the day, before I shut the tractor down I'll raise the throttle and curl the bucket until the hydraulics bypass, then hold the function for 15-20 seconds. This puts a load on the engine and raises the DOC's temp, burning off the accumulated soot and producing a cloud of blue/gray smoke. Once it clears up I'll idle down for a minute to let things cool, then shut down.
Last edited: