Smoky Diesel, what to do?

[Weekend Yachtsman]

I have a Beta BD662, 1993 vintage, which smokes like the proverbial factory chimney. It has been affected by water inside, in the past, due to an installation error by a previous owner, but that's now fixed. Total engine hours are probably about 2000, but it's hard to be sure because the instruments have been replaced at least twice - once after a fire, and once to install an all-push-button panel.

Starting is quite good - it always starts, but it always needs 10 secs or so of pre-heat. It smokes on startup, and the smoke dies down after a few seconds. But it also smokes, constantly, from the crankcase breather. After a few minutes running (especially at idling or low speed on load) the cockpit lockers are full of smoke and there are unpleasant fumes in the cabin.

The air filter is changed every year, the oil and filter twice a year. The injectors and high-pressure pump have been calibrated and serviced, the valves and valve guides have been replaced. I used a cylinder guage on it when the head was off, and the cylinders are not out-of-spec on roundness. In fact they are pretty good. I don't have any way of checking compression.

I am thinking piston rings. Anyone got any other thoughts?

 

[vyv_cox]

Piston rings is a good possibility, but in view of the history of water inside could the bores be pitted? Would amount to the same thing, oil passing the rings. This assumes blue smoke, evidence of oil burning. Smoke from the crankcase breather suggests the same.

Compression can be checked roughly by turning the engine over using a tommy bar on the crankshaft nut, or similar. It should be quite difficult to turn it over TDC and the same on all cylinders.

 

[Jassira]

sounds like it needs reboring etc.. but if it's running well otherwise it might be worthwhile routing your crankcase breather back into the air filter, a bit like putting a bucket under a leaky deck perhaps, but just might stop you gassing the off watch creww.

 

[TQA]

If it is from the crankcase breather it is either piston or valve guide blow by.

As a POSSIBLE FIX and you need to do this with some awareness of the possible engine runaway situation why not try fitting some sort of crankcase ventilation valve and then running the crankcase blowby into the inlet manifold.

The PCV prevents the suction from the inlet manifold drawing stuff from the crankcase, the idea is that over pressure in the crankcase gets fed to the inlet manifold.

BUT BE AWARE that if the engine can suck in hot crankcase oil it can runaway on this.

 

[Heckler]

If it is from the crankcase breather it is either piston or valve guide blow by.

As a POSSIBLE FIX and you need to do this with some awareness of the possible engine runaway situation why not try fitting some sort of crankcase ventilation valve and then running the crankcase blowby into the inlet manifold.

The PCV prevents the suction from the inlet manifold drawing stuff from the crankcase, the idea is that over pressure in the crankcase gets fed to the inlet manifold.

BUT BE AWARE that if the engine can suck in hot crankcase oil it can runaway on this.

If an engine is puffing from the breather then the gas is getting past the pistons, the only place it can come from. It wont get past the valve guides, think about it! Diesels have wide open inlets so no pressure in the inlet tract (in petrol engines with a throttle the opposite happens, throttle closed = vacuum, so oil goes down the inlet valve guides when it is shut)
They also have wide open exhausts so the only slight pressure is when the silencer is having water pushed out. In all my years of experience, valve guides have never been an issue from the point of view of smoking crankcase breathers.
My MD22 has a pipe going from the oil filler tube to the inlet mushroom strainer, this directs any fumes to the inlet strainer where they are sucked in to the inlet of the engine and burned. By putting the pipe to the strainer, (http://www.marinepartseurope.com/en/volvo-penta-explodedview-7746710-25-2850B.aspx item 41) it isnt a direct feed to the crankcase oil and so oil cannot be sucked in directly.
Stu

 

[mattnj]

if its otherwise running ok, i would be tempted to just go for the easy option, vent it either into the air inlet, or you could just vent it straight to the outside with a skin fitting...

 

[boatmike]

Hate to be controversial but the posts suggesting routing the breather back into the intake is indeed dangerous. Please don't do it. I agree it's unlikely to be valve guides on a diesel. Badly worn guides can cause smoke on the exhaust but unlikely to be a cause of sub piston pressure which is most likely worn bores or broken/worn rings. Probably both in fact and its very rare when it gets to this state that you get by without a rebore. Only an inspection will tell though, and while its down inspect the BE bearing shells. If these are worn the main bearings probably will be too so budget for the worst and hope for the best!

 

[steve28]

yanmar gm engines rebreathe in this way ?, why not in this instance

 

[Heckler]

Hate to be controversial but the posts suggesting routing the breather back into the intake is indeed dangerous. Please don't do it. I agree it's unlikely to be valve guides on a diesel. Badly worn guides can cause smoke on the exhaust but unlikely to be a cause of sub piston pressure which is most likely worn bores or broken/worn rings. Probably both in fact and its very rare when it gets to this state that you get by without a rebore. Only an inspection will tell though, and while its down inspect the BE bearing shells. If these are worn the main bearings probably will be too so budget for the worst and hope for the best!

Read my post again, the MD 22 does it as std. In fact Id go so far as to say the vast majority of internal combustion engines do it nowadays. It all started in the 70s when California poluution rules came in to force.
Stu

 

[njthake]

"I used a cylinder guage on it when the head was off, and the cylinders are not out-of-spec on roundness. In fact they are pretty good. "


If the cylinders are ok. Then having suffered what sounds like raw water ingress via the exhaust, and the water was standing in whichever cylinder had it's exhaust valve open, then the damage is in the rings and piston. The piston probably suffered worst because it is aluminium alloy. The ring groves are enlarged and sloppy.

The breathing in the crankcase (blowby) is combustion gas that has passed the gas tight seal of the piston and now pressurises the crankcase.

You cannot cure this without surgery. The venting of the crankcase directly to the intake manifold will get rid of the smell but will not cure the problem. The redirection of the crankcase breather without specific blow/off protection can cause embarrasing problems if the rings/piston were to fail. The excess pressure causes the crankcase (full of oil) to empty its contents into the intake manifold and the engine to runaway. Over RPM and no throttle response/shut off until the crankcase oil is exhausted!! Or a rod peeps out the side!

Best to breather overboard until it can be fixed.

Nick

 

[tim_ber]

I know a tiny amount about diesels, but with turbos.

I'll pass it on in case it is of use. Some of it may be wrong and totally not applicable to marine engine.

Black smoke can mean overfueling. Blue is oil burning. (So I was told)

My turbo was not working properly, therefore too little air, therefore too much fuel, = black smoke. Fixed turbo, all OK.

Also, an additive (and a truly good professional use one only) is Forte. Google it. You can only purchase it from mechanic's garages, not Halfords etc.

There is a diesel additive - cleans all fuel delivery - tanks to injectors. Also an oil additive - cleans 'varnish' from around piston rings etc.

Used both and noticed appreciable differences - paid £15 per bottle from my local garage.

Or search this forum and google "Seafoam" - an american additive about which I know nothing, but it states that it de-cokes the head????

 

[Heckler]

"I used a cylinder guage on it when the head was off, and the cylinders are not out-of-spec on roundness. In fact they are pretty good. "


If the cylinders are ok. Then having suffered what sounds like raw water ingress via the exhaust, and the water was standing in whichever cylinder had it's exhaust valve open, then the damage is in the rings and piston. The piston probably suffered worst because it is aluminium alloy. The ring groves are enlarged and sloppy.

The breathing in the crankcase (blowby) is combustion gas that has passed the gas tight seal of the piston and now pressurises the crankcase.

You cannot cure this without surgery. The venting of the crankcase directly to the intake manifold will get rid of the smell but will not cure the problem. The redirection of the crankcase breather without specific blow/off protection can cause embarrasing problems if the rings/piston were to fail. The excess pressure causes the crankcase (full of oil) to empty its contents into the intake manifold and the engine to runaway. Over RPM and no throttle response/shut off until the crankcase oil is exhausted!! Or a rod peeps out the side!

Best to breather overboard until it can be fixed.

Nick

"The excess pressure causes the crankcase (full of oil) to empty its contents into the intake manifold and the engine to runaway. Over RPM and no throttle response/shut off until the crankcase oil is exhausted!! Or a rod peeps out the side!"

No not really, on the MD22 for example, the crank case breather is on the top of the oil filler, way above where the oil is.

Any way the runaway situation happens mainly in 2 stroke supercharged diesels where the oil seals go in the blower and raw lube is pumped in to the intake.
Stu

 

[Heckler]

Snake Oil!
Stu

 

[vyv_cox]

Snake Oil!
Stu

Exactly so!

 

[oldharry]

Snake Oil!
Stu

Definitely. Nothing in a bottle will help worn or damaged piston rings, which is what this is all about.

Routing the crankcase vent in to the air manifold is standard practice on most if not all road diesels, and many newer marine engines too. This works fine until you start getting excess crankcase pressure, and oil mist gets pushed in to the manifold via the breather. Run the engine hard and sufficient oil accumulates in the manifold for the engine to start running on it - and that is scary! I had it fairly regualrly on an old Sherpa van until I got round to replacing it. Drive the van too hard and the engine would run away out of control for 30 seconds or so producing a huge cloud of grey smoke. It would always start and run normally after I had changed my trousers.... Tough engines those old 2l Perks)

However, I would be a little careful about suggesting doing it on an engine where the breather system was not designed for it. Manifold suction on the breather could actually suck oil out causing major problems at speed.

Turbos introduce a whole new area, but a failed turbo can produce a similar result when the seals go, allowing boost pressure into the crankcase via the oil return pipe.

The indications are that you have piston/ring problems, which will not go away without surgery, so you will have either to live with it, or bite the bullet.

 

[Heckler]

Definitely. Nothing in a bottle will help worn or damaged piston rings, which is what this is all about.

Routing the crankcase vent in to the air manifold is standard practice on most if not all road diesels, and many newer marine engines too. This works fine until you start getting excess crankcase pressure, and oil mist gets pushed in to the manifold via the breather. Run the engine hard and sufficient oil accumulates in the manifold for the engine to start running on it - and that is scary! I had it fairly regualrly on an old Sherpa van until I got round to replacing it. Drive the van too hard and the engine would run away out of control for 30 seconds or so producing a huge cloud of grey smoke. It would always start and run normally after I had changed my trousers.... Tough engines those old 2l Perks)

However, I would be a little careful about suggesting doing it on an engine where the breather system was not designed for it. Manifold suction on the breather could actually suck oil out causing major problems at speed.

Turbos introduce a whole new area, but a failed turbo can produce a similar result when the seals go, allowing boost pressure into the crankcase via the oil return pipe.

The indications are that you have piston/ring problems, which will not go away without surgery, so you will have either to live with it, or bite the bullet.

Harry
half right! turbo shaft floats on oil in the bearings produced from the engine oil pressure. If the seals go, the oil goes in to the turbo, not the piffling little bit of boost pressure going the other way. By the time the turbo is spewing oil out the engine will have come to a stop anyway
By the way my MD22 is a derirative of the montego/sherpa/perkins engine BUT the mushroom strainer on the inlet is "wide open" so oil wont "accumulate in the manifold"
Plus most breathers are taken from places "away" from the crankcase oil.
Stu

 

[oldharry]

Harry
half right! turbo shaft floats on oil in the bearings produced from the engine oil pressure. If the seals go, the oil goes in to the turbo, not the piffling little bit of boost pressure going the other way. By the time the turbo is spewing oil out the engine will have come to a stop anyway
By the way my MD22 is a derirative of the montego/sherpa/perkins engine BUT the mushroom strainer on the inlet is "wide open" so oil wont "accumulate in the manifold"
Plus most breathers are taken from places "away" from the crankcase oil.
Stu

Ok didnt know the MD22 was Perk based, but what I described was exactly what happened to my old non turbo Sherpa Perkins if I pushed it too hard. It was VERY worn, bores almost ovalled to the first rebore, and rings gapping nearly x2 spec. Probably around 400k on the clock. It still started and ran perfectly up to around 3k revs, incredibly. After that it started blowing enough oil into the manifold to cause problems. I replaced it with a recond turbo engine from a Montego, but didnt replace the turbo, which later failed and pressurised the crankcase again, causing it to run away on lube exactly as before. Another turbo from the breakers sorted it. It actually made it quite a decent van to drive with reasonable acceleration . A turbo specialist (natiuonal company) advised me that the crankcase pressure would come from the failed turbo, and there was no more pressurisation after the new turbo was fitted. That and a bit more smoke was the only symptom of the failed turbo, the rotor of which had a lot of play compared to the repalcement.

The Perk Montego version had the breather tube coming up the side of the engine from an orifice just above the sump, with an oil seperator up to a sealed filler cap. A pipe took crank case fumes back to the air filter housing, feeding it into the air pipe to the manifold. The entire manifold on the original engine was thick with oil, and it was pushing about half a litre of oil an hour into the manifold. As I didnt want to take the van off the road at that point and it started and ran perfectly provided I didnt push it too hard, I cut the breather/ manifold pipe, and fed it through an old oil can as a secondary oil separator. The drill was to stop every hour or so, and tip the oil back into the engine. Yes I know, but I already had a recond engine to replace it when I had time. It actually survived around 6 months and several 1000 miles like that!

 

[mattnj]

just vent it over the side, simple, easy, no risk of it running away, no need for a new engine...

downside? a bit of extra pollution, but hey, doesnt sound like its ever going to be a very "green" engine anyway.