engine smoke

[frank]

Some advice please - our HR29 is fitted with a volvo penta 18hp diesel engine, now 14 years old. Tail end of last season the engine started to smoke really badly after it had been run for about ten minutes, the smoke is white/greyish. I'm not sure if its steam or unburnt fuel. anyway, we had it serviced and the engineer didn't see any problems with it but it continues to bellow smoke. Any idea of what is causing this and if we continue to run it like this are we likely to cause any long term damage?
Thanks

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[freebird1]

There has been a lot of threads on the smoke / steam issue. If it is happening AFTER about ten minutes, i would have thought this is more likely steam. Diesels tend to be smokey at start up not the other way round. I'd start by checking your impeller. Has there been a reduction in cooling water coming out of the exhaust? Does the flow seam to reduce as the 'smoke' starts? Is your engine raw water cooled or do you have a heat exchanger? You could hold a (cold) plate in the smoke and see if water droplets condense on it - although a bit rough and ready, this would give you a clue it it is steam or smoke. Steam tends to disperse quickly and is more noticeable at the ends of the season.

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[steve28]

you do say the tail end off last season, are you sure its not just because of cold air ?



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[Born_Free]

Do the above tests for steam, but as you say it is white/grey smoke this could indicate unburnt fuel, so when did you last have your injectors and high pressure pump serviced-worth looking into, also worth checking that the pump timing hasn't slipped a little, both of these can cause this problem, although if it doesn't occur until the engine is warmed up it is more likely to be steam than fuel, but the grey colour points to fuel. Did your service engineer do a compression test, this may be worth doing as the head may be losing it's seal as it warms up, and then leaking, firstly check for creamy white froth on the fresh water filler cap and the oil filler cap which would indicate a blown head gasket, if that's O.K. then check to see if you have excessive pressure in the engine coolant, which would indicate the same problem, all assuming it is fresh water/heat exchanger cooling of course. These checks should enable you to find the problem.
Best to sort it out sooner rather than later, as it's always cheaper to fix an engine that's still running than a dead one.
Good Luck

<hr width=100% size=1>I have nothing to declare, except my genius
(Sorry Oscar)

 

[frank]

Thanks for that - the engine is fresh water cooled. The injectors haven't been serviced so that may be the problem but I'll check out the oil filter cap and the fresh water filler cap for creamy white froth. I'm still concerned that if I keep running it like this what's likely to happen?
Thanks again.

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[oldharry]

Its difficult to tell the difference between white smoke and steam. It is normal for an older diesel to push white smoke for a few minutes after starting from cold, but unusual for it to smoke after it has warmed up, unless there are other symptoms such as power loss, or if it has been subjected to extended cranking to start it. If it is otherwise running OK its far more likely to be steam caused by insufficient water reaching the exhaust due to a partial blockage of the cooling system, or damaged pump giving reduced output. The exhaust would be overheating and producing the steam. Often the first hint of cooling trouble I get on my boat is the appearance of steam in the exhaust.

Compression testing - unlike on a petrol engine - will tell you very little about a diesel, and in my experience is not a useful diagnostic tool for a small engine. Pressures are so much higher in a compression ignition engine that few faults will show up clearly at cranking speed/pressures.

White froth being pumped into the header tank is indicative of compression loss usually from the head gasket or very rarely a cracked head or block. Valve faults can show up as knocks, rattles, wheezes, misfiring and white smoke in any combination of symptoms, while piston faults (worn/broken rings), bore glazing or damage show up as increased pressure in the crancase, which will soon start blowing oil through the breather. Block off the breather for 8 -10 seconds with then engine running - if there is a 'whoosh' of air when you release it, you have piston or ring trouble. Dont block it off too long or you will blow the engine oil seals out!

White smoke as such is caused by unburnt atomised diesel from the injectors being passed into the exhaust, either because the injectors are malfunctioning or there is insufficient heat and compression to ignite it fully. Also if you have cranked the engine for a long time without it starting, the exhaust manifoild etc gets covered in diesel, which then boils off as white smoke for quite a long time once the engine warms up - can be up to half an hour before it clears on a dry exhaust system!

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[frank]

Thanks for that. checked for white froth - not a trace. I checked the exhaust and I think I may have a cooling problem. The amount of water through the cooling system seems very poor, maybe a partial blockage - sod's law says it's in the sail drive leg and we just put the boat back in the water. Can the cooling system blockage be cleared with the boat in the water? And just to compound the problems with this damn engine- we were taking it out of the marina, put it in gear nice and gently and bang, thought the engine was trying to leap out of the bottom of the boat, terrible vibration. Checked the engine mounts and the front two both gone. Can't understand why. Last sail, motored in nice and smooth no problems. Thing is we keep engine use to an absolute minimum and never overload it - unbelievably irritating and expensive!

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[Spyro]

Hi Frank
Bigger boat bigger problems... sorry to read of all your problems but better now than in the middle of summer. I don't know the kind of set up with a sail drive re' cooling but I would have thought it's via an impellor type pump mounted some where on the engine and not in the leg, Try replacing the impellor it should be done every year anyway as they do break up and wear down. Also You should be able to follow from the cooling water skin fitting via a valve to the pump. There may also be a filter somewhere in between that could need cleaning. (that's the simple things it could be). As for the engine mounts I was advised to replace all four. hopefully it won't be to much bother The problem I had was that I couldn't get original yanmar ones and the replacements had wider bolts so the feet on the engine had to be drilled out which meant removing the engine to get access to them... Not trying to frighten you I'm sure you will still be able to get like for like replacements.

Good luck
See you some time over the summer
Ian



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[frank]

Ian,

Thanks for that, right enough, bigger boat, bigger problems!- we had the impeller changed this year - I suppose with all this happening at once I'm just expecting the worst and that the blockage is where I can't get access to it. Hope things are still fine with Booby Trapper and you're still enjoying it - have you had her out this year yet? No doubt see you over the coming weeks.

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