White Smoke (Steam?) from Exhaust

[Spirit (of Glenans)]

My VP D1-20 has previously been well behaved and trouble free. Unfortunately, last time out I noticed some white emissions from the exhaust when running at 2300 revs. Even though the normal volumes of water were coming from the exhaust, I thought it might be steam and shut down and checked the impeller, exhaust temperature, coolant header tank etc to find nothing amiss, so started up and proceeded at lower revs and got back to the marina without incident.
On running it up in gear , it runs fine at up to 1800, but when increased to 2000 revs it starts to blow white smoke/steam, with no unusual sound or misfiring, and seems to giving plenty of thrust when run in forward or reverse. I'm not sure which it is, but it does not seem to hang around in a pall, like smoke, but dissipates quickly, as steam would.
Should I be checking the cooling system or would the fuel filters and injectors be the cause of this, (the remaining diesel in the tank dates back at least a couple of years)?

 

[Topcat47]

Wait for Viv Cox to come along. He'll set you right. Alternatively PM him. His advice is always sound and on the occasions when it differs from mine, he's always been right. If this doesn't work, we can always have a pop, but he's there guru.

 

[Seamechanic]

Hi,
I'd go for the cooling system!
We have had the very same effect with our VP2002 in 2016 (our first year with the boat).
Running perfect, power enough but smoking/steaming under full (almost full) throttle.
I've cleaned the cooling system with vinegar acid before leaving the water for winter break.
Since the beginning of 2017 we don't have a steam engine anymore. The engine runs smokefree even under full load.
The amount of water coming out of the exhaust seems to have increased but that's not verified.
Frank

 

[neil_s]

I'm having the same problem with my Bukh. It's about 4 years since I cleaned out the limescale so maybe it's coming up to time to do it again for me too. Perhaps water flow is still good and the body of the engine is staying within temperature range but there are hot spots developing in the cylinder head and exhaust manifold that generate the steam.

 

[VicS]

My VP D1-20 has previously been well behaved and trouble free. Unfortunately, last time out I noticed some white emissions from the exhaust when running at 2300 revs. Even though the normal volumes of water were coming from the exhaust, I thought it might be steam and shut down and checked the impeller, exhaust temperature, coolant header tank etc to find nothing amiss, so started up and proceeded at lower revs and got back to the marina without incident.
On running it up in gear , it runs fine at up to 1800, but when increased to 2000 revs it starts to blow white smoke/steam, with no unusual sound or misfiring, and seems to giving plenty of thrust when run in forward or reverse. I'm not sure which it is, but it does not seem to hang around in a pall, like smoke, but dissipates quickly, as steam would.
Should I be checking the cooling system or would the fuel filters and injectors be the cause of this, (the remaining diesel in the tank dates back at least a couple of years)?

Your D1-20 is indirectly cooled. If what you see is steam the only way in which the cooling water can be hot enough to steam is if the flowrate is too low.

If you have changed the pump impeller then I would be looking for anything that might be limiting the flow rate from the inlet strainer through the HE to the water injection into the exhaust.

 

[marivor]

Hi I had the same symptoms and it was the exhaust water injection point blocked. Had to replace elbow as the hose connection had collapsed.

 

[Caer Urfa]

Hi

When you have looked at everything else and found nothing then have a good look at your heat exchanger as the coil may be perforated,
are you sure at 'higher revs' there is not less water discharging from the exhaust outlet ??

 

[Spirit (of Glenans)]

Hi

When you have looked at everything else and found nothing then have a good look at your heat exchanger as the coil may be perforated,
are you sure at 'higher revs' there is not less water discharging from the exhaust outlet ??

Seems to discharge water at the same rate across the rev range.

 

[robertj]

I'm having the same problem with my Bukh. It's about 4 years since I cleaned out the limescale so maybe it's coming up to time to do it again for me too. Perhaps water flow is still good and the body of the engine is staying within temperature range but there are hot spots developing in the cylinder head and exhaust manifold that generate the steam.

VYV Cocks will bear this out but nearly all Bukh’s steam. Mine did and does

 

[vyv_cox]

Thanks for the confidence in my advice! I suggest that if there is no visible blockage in the external parts, strainer, impeller, exhaust manifold, thermostat, etc., then the most likely cause is the engine coolant passages. The symptoms sound very much like this anyway. Google Rydlyme for their treatment method, although it requires the use of an additional pump. The product seems to be hydrochloric acid, so for an easier and cheaper method buy brick acid, fill the engine fully with it through the thermostat housing or highest point, leave for about 30 minutes and flush through. There are more involved methods but this one does work. The acid will bubble and froth as the carbonate is reacted so watch out for splashes. Remove anodes first and plug the ports.

 

[Topcat47]

See, what did I tell you?

 

[Stemar]

Every now and then I have this problem. In my case, it's usually due to barnacles in the water intake.

I've nowhere near Vic's level of expertise, but I wouldn't have thought limescale would be a common problem with an indirectly cooled engine as it only has (should have) fresh water with antifreeze running through it. It's far more likely to happen on an directly cooled one with seawater going through it.

 

[vyv_cox]

Sorry, you are right. I don't know Volvo engine types and assumed it was directly cooled. If it is overheating at higher revs the cooling system is not working as efficiently as it should. I would look at the heat exchanger. Sometimes broken impeller blades lodge in the inlet plenum or there could be deposits that restrict flow.

 

[Fr J Hackett]

Any possibility of it being unburnt diesel?

 

[VicS]

Any possibility of it being unburnt diesel?

See #1 for the OP's thoughts on this

 

[Fr J Hackett]

See #1 for the OP's thoughts on this

Diesel tends to be mistaken for steam and does disperse reasonably quickly, I only say because I once had an old Bukh with similar symptoms getting the injectors calibrated solved the issue.

 

[Topcat47]

I'd have to ask where the unburnt diesel is coming from. In my experience, overfueling leads to black smoke. There's a water trap in most exhaust systems and unburnt fuel gets mixed with the water ejected from the exhaust. Some exhaust systems separate the water from the gases and they exit from different hull fittings. You get gases from the main outlet and a stream of water from another like the tell tale in an outboard. In such cases, if not enough salt water is getting through to the engine exhaust, it is possible that the water in the trap is evaporating and causing the white smoke. This may be due to salt encrustation in the raw water side. In FW cooled engines, the engine coolant is separate. If the engine overheats, there is a pressure cap in the system.

 

[Stemar]

IIRC, black smoke is too much fuel being injected, so it burns partially. Dirty injectors can cause black smoke if the droplets are too big to combust properly

White smoke is fuel that leaks into the cylinder as a liquid, so it doesn't ignite, it just vaporises before getting pushed out of the exhaust valve.

 

[longjohnsilver]

I had a similar problem last year on my Ford based Lehman engine. I checked all the obvious potential culprits, impeller, heat exchanger, inlet seacock, and then rydymed the whole kaboosh.

In the end I discovered that the outlet port of an in-line stabiliser cooler was almost completely blocked with a salty calcium deposit, although the cooler itself was clear. There was only a hole thinner than a pencil letting water through. It seemed to the naked eye that the flow from the exhaust was normal and the engine, surprisingly, was not overheating.

So look at everything and don’t, as I did, make assumptions. Strangely the inlet side of the cooler was completely clean.

 

[Mike k]

I had a similar problem and after pump change, rydlime use, elbow checks it turned out to be the basket in the strainer. The lid is clear and have always looked to see it was ok hence I had steam for 5 years ( no problems though) but once I took out the basket a film on the surface to the exit part going to the cooling system had developed which was not visible to eye which was restricting flow enough to cause a hot spot. Always now periodically remove and physically check/clean the basket and turn it around in the strainer. I know I should have not relied on visual checks but I have learned my lesson