Cleaning exhaust elbow

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npf1

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I've got my exhaust elbow off at present. It's working fine but looks to be rather gunked up with barnacles so I'd like to get it fully cleared before I put it back on. I've soaked it in oxalic acid for 24 hrs and then caustic soda for a few hours but neither has moved much of the crap. What should I be using the shift the stuff? Or shouldn't I bother?

Thanks
 
[ QUOTE ]
gunked up with barnacles

[/ QUOTE ] ??!! The Exhaust elbow that connects your engine to the exhaust pipe is covered with barnacles? I'd say you've got more of a problem than just the barnacles! How did they get there and how do they stand the heat?!
 
Dunnow - guess need to ask a marine biologist abut that one! Perhaps not barnacles but look like it. There's some rust there too but the elbow all seems to be very solid so should have plenty of life in it yet.
 
Are you sure they are not carbon deposits from the combustion process?

If so, then I had this problem too, although it was sufficiently severe to "choke" the engine running. I too tried very concentrated caustic soda (mind your lungs!) together with a hammer and old chisel. I succeeded in clearing it sufficiently to contiinue use, but the elbow's inner liner was damaged in trying to break the carbon out. So I replaced the elbow shortly after. Reckon the carbon buildup was the result of not getting the injectors serviced in a timely manner and not thrashing the engine enough from time to time to burn out the carbon buildup. I've not yet checked the new elbow, which is now a year old.
 
Could well be carbon as I've never run the engine at high revs to burn off build up.

Incidentally, how should the engine be thrashed to burn off the build-up? In gear/in neutral? For how long? I've watched cruise ships doing it with generators - seem to remember the ones in Palma ran their gensets at full chat (prob not under load) for a while each Saturday, much to the dismay of various superyacht deckhands!!!
 
I was reading an article on this very subject in the Moody Owners mag - apparently a few applications of hydrochloric acid will soften up the carbon deposits and leave it as good as new.

Obviously a potentially hazardous job not to be performed at sea.
 
did it say what conc of Hydrochloric acid? Brick acid?

Also, I found this in a Cummins manual regarding burning off carbon etc:

GENERATOR SET EXERCISE
Regular exercising keeps engine parts lubricated, prevents oxidation of electrical contacts, uses up fuel before it deteriorates, and, in general, helps provide reliable engine starting. Exercise the generator set at least once a month for a minimum of 30 minutes loaded to no less than one-third of the nameplate rating. Periods of no-load operation should be held to a minimum, because unburned fuel tends to accumulate in the exhaust system. If connecting to the normal load is not convenient for test purposes, the best engine performance and longevity will be obtained by connecting it to a load bank of at least one-third the nameplate rating.
 
No it didn't say anything about concentration. I assumed it was neat (but I know nothing about these things).

Several other posts on the subject just referred to fitting a new elbow. The important thing is to clear it so that the engine can breath properly. Perhaps it depends on your abilities or wallet!
 
We had our exhaust elbow decoked by the Yanmar agent in Southampton last winter - when they replaced the saildrive diaphragms (supposedly a 2 year job on Yanmars - wonder how the insurance would view a failure after that time). The removal, sandblast/decoke and refit was about £90 . Replacing the saildrive seals was £1000 !

Can't say the decoke made an obvious difference - if I remember, the Yan mar manual states that the engine should be run at full power for a few minutes every couple of hours.
 
i had the same problem with my Volvo 2003T the other y. none of the chemicals mentioned and more stuff helped - the remedium was to heat it up - maybe over 400 degrees C also taking a little risk to crack the alloy. now heated up u notice u are ready when the ss inlet (anyway in my engine) gets free from the outer part and the "barnacles" ( /forums/images/graemlins/laugh.gif). It will also now be possible to finish the cleaning job mechanical. /forums/images/graemlins/cool.gif
 
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