Smoking engine

[richardsnowstar]

I have a 27 year old Bukh 36 in my boat and it has always smoked a little bit when starting in the 3 years I have owned it. However now it is smoking a lot more when starting and depositing an oily film on the water.

In the past it has not been using much oil but I have not used it enough this year to check this.

When I relaunched after the winter I stupidly left a rag plug in the air filter and ran it for a couple of miles before realising the problem. The symptoms with the rag insitu were lack of power and revs and a lot of soot from the exhaust.

Has anyone got any suggestion about what may be the cause of the smoking exhaust now? Could it be that the rag in the air filter has caused the injectors to clog up or caused damage to the engine? Shoud I try some form of injector cleaning?

Any help will be welcome.

 

[grazbo]

My guess would be your oil is now contaminated with diesel due to lack of air previously.

Is the film on the water oily or sooty ? If sooty I would look at the exhaust elbow

Clogged injectors would cause it to run lumpy and low power at top end with black smoke.

Naked sense ?

 

[Heckler]

My guess would be your oil is now contaminated with diesel due to lack of air previously.

Is the film on the water oily or sooty ? If sooty I would look at the exhaust elbow

Clogged injectors would cause it to run lumpy and low power at top end with black smoke.

Naked sense ?

uhh!

 

[NDG]

I had a similar problem last year, with grey smoke and a sooty deposit on the water. It was the exhaust elbow, which was easy to replace. However a complication was that the inlet and exhaust valves had become clogged with sooty carbon deposits - I had been running the engine whilst trying to work out the cause of the problem - and I had to have the head stripped and cleaned.

If it is the elbow I would recommend looking at it and replacing it before running the engine again in case you cause similar complications.

Hope that helps.

 

[vyv_cox]

The throttling of the inlet air cannot possibly have affected the injectors and is most unlikely to have done serious damage to the engine. I agree with NDG that checking the exhaust elbow for partial blockage is worthwhile. After that I would run the engine at full revs, driving the boat, for about 15 minutes, the technique known as the 'Italian tuneup'. This has the effect of burning off carbon deposits and will usually improve a smoking and underpowered engine

 

[richardsnowstar]

My guess would be your oil is now contaminated with diesel due to lack of air previously.

Is the film on the water oily or sooty ? If sooty I would look at the exhaust elbow

Clogged injectors would cause it to run lumpy and low power at top end with black smoke.

Naked sense ?

Thanks for the advice. The water below the exhaust has an oily film now. When the rag was still in the inlet the film left on the water was definately sooty, so much that I attracted the attention of the Portsmouth Harbour MP.

I will have a look at the exhaust elbow. However I am not sure how this would introduce oil to the exhaust. Is it possibly due the earlier rich running leaving a deposit on the inside of the elbow?

 

[richardsnowstar]

Thanks NDG and Vyv. Will check the exhaust elbow and then try the italian tune up.

 

[richardsnowstar]

I have removed the exhaust elbow and discovered it was very sooty but also very corroded and needs replacing.

I also removed the exhaust manifold and this is very sooty, maybe about 2mm thick. Do you think this may indicate problems inside the engine?

Another problem that has turned up is leaking cooling water (raw water cooled engine). This has turned out to be the water pump seal and some water has gone into the engine oil. I know this is relatively recent because I checked the oil level less than 10 hours running ago and I would have noticed the emulsified oil. Is it possible this has something to do with the smoking exhaust?

Any advice would be appreciated.

 

[haydude]

The throttling of the inlet air cannot possibly have affected the injectors and is most unlikely to have done serious damage to the engine. I agree with NDG that checking the exhaust elbow for partial blockage is worthwhile. After that I would run the engine at full revs, driving the boat, for about 15 minutes, the technique known as the 'Italian tuneup'. This has the effect of burning off carbon deposits and will usually improve a smoking and underpowered engine

Agree, just make sure that you are in gear, which means sailing, do not run the revs up in neutral, diesel engines do not like that and may get damage.

 

[vyv_cox]

I have removed the exhaust elbow and discovered it was very sooty but also very corroded and needs replacing.

I also removed the exhaust manifold and this is very sooty, maybe about 2mm thick. Do you think this may indicate problems inside the engine?

Another problem that has turned up is leaking cooling water (raw water cooled engine). This has turned out to be the water pump seal and some water has gone into the engine oil. I know this is relatively recent because I checked the oil level less than 10 hours running ago and I would have noticed the emulsified oil. Is it possible this has something to do with the smoking exhaust?

Any advice would be appreciated.

I don't think the smoking would be caused by water contamination of the oil but cannot completely rule it out. I am guessing that the presence of water in the lubricant might allow more oil to pass the rings, which would normally result in blue smoke but also would coke up the exhaust system. The one thing that is certain is that you need to replace the oil immediately, as seawater in it will do no good at all. You also need to check the water pump carefully, not just the seals but other components also. There are many photos on my website, under Engine>water pump (surprisingly )

After changing the oil and replacing exhaust elbow and water pump parts I would try the Italian tuneup first. If smoking persists you may need to investigate further.

 

[richardsnowstar]

I have now been told that the water pump seals are designed with 2 seals so that if the water or the oil ones go then the leak comes out between the seals so that cross contamimination is very difficult. So now I am stumped as to where the water is getting into the oil. Any suggestions?

 

[vyv_cox]

I have now been told that the water pump seals are designed with 2 seals so that if the water or the oil ones go then the leak comes out between the seals so that cross contamimination is very difficult. So now I am stumped as to where the water is getting into the oil. Any suggestions?

Look at the photos about 6 or 7 down on this page. It's a Bukh engine whose piston rings rusted to the bores due to water that passed the seals. You are correct that the seals in the water pump are mounted back-to-back to keep both oil and water inside. If the water side seal fails the water will emerge from the tell-tale hole, provided the flow is small. When the flow is greater it is easier for water to enter the engine via the oil seal, which is not able to seal, being the 'wrong' way round, than it is to exit the small hole. It can also happen that the small hole is blocked by internal debris or external paint. This is an extremely common failure, so I am afraid your informant is incorrect.

 

[aztec]

I have a 27 year old Bukh 36 in my boat and it has always smoked a little bit when starting in the 3 years I have owned it. However now it is smoking a lot more when starting and depositing an oily film on the water.

In the past it has not been using much oil but I have not used it enough this year to check this.

When I relaunched after the winter I stupidly left a rag plug in the air filter and ran it for a couple of miles before realising the problem. The symptoms with the rag insitu were lack of power and revs and a lot of soot from the exhaust.

Has anyone got any suggestion about what may be the cause of the smoking exhaust now? Could it be that the rag in the air filter has caused the injectors to clog up or caused damage to the engine? Shoud I try some form of injector cleaning?

Any help will be welcome.

Remove injector/s, take to a diesel workshop (most will have a pressure tester) what you're looking for is good spray pattern and opening pressure. I suspect that it/they needs a service.

Running with a rag in the inlet won't damage the engine, just prevent it from taking in enough air to burn the fuel. If the injector is incorrectly atomising the fuel or "dribbling" then the fuel will not be burnt completely, hence the "unburt" diesel or smoke.

Good luck.

 

[rafiki_]

I have removed the exhaust elbow and discovered it was very sooty but also very corroded and needs replacing.

I also removed the exhaust manifold and this is very sooty, maybe about 2mm thick. Do you think this may indicate problems inside the engine?

Another problem that has turned up is leaking cooling water (raw water cooled engine). This has turned out to be the water pump seal and some water has gone into the engine oil. I know this is relatively recent because I checked the oil level less than 10 hours running ago and I would have noticed the emulsified oil. Is it possible this has something to do with the smoking exhaust?

Any advice would be appreciated.

Note your other thread, I think you have a head gasket problem.

 

[richardsnowstar]

Look at the photos about 6 or 7 down on this page. It's a Bukh engine whose piston rings rusted to the bores due to water that passed the seals. You are correct that the seals in the water pump are mounted back-to-back to keep both oil and water inside. If the water side seal fails the water will emerge from the tell-tale hole, provided the flow is small. When the flow is greater it is easier for water to enter the engine via the oil seal, which is not able to seal, being the 'wrong' way round, than it is to exit the small hole. It can also happen that the small hole is blocked by internal debris or external paint. This is an extremely common failure, so I am afraid your informant is incorrect.

Vyv - Thanks for the information. My water pump has fairly large slots which are only partially blocked between the seals. But the water leak was significant. Do you still think it is this and not the head gasket?

 

[vyv_cox]

Vyv - Thanks for the information. My water pump has fairly large slots which are only partially blocked between the seals. But the water leak was significant. Do you still think it is this and not the head gasket?

If the bilge remained dry it would seem to indicate that the pump is not the source of the water in the oil. The pump is only held on by a couple of bolts, so it's easy to pull it off and check the condition of the oil seal and surrounding metal.