Captain Crisp
Well-Known Member
Hi, after much jiggery-pokery I got the exhaust elbow off my VP MD 2010, only to discover that most of the build up is in the actual engine side... what do I do? Chip it out? How?
Cheers!
Cheers!
How to remove carbon build up in exhaust?
- Thread starter Captain Crisp
- Start date
Tranona
Well-Known Member
Primary cause is not running the engine hard enough and hot enough.
No magic way of removing except chipping it away but not easy with the manifold in place.
No magic way of removing except chipping it away but not easy with the manifold in place.
Captain Crisp
Well-Known Member
Yes... not sure I'm qualified to remove the whole manifold yet... do I need to worry about knocking bits of rubbish back into the engine at all?
Captain Crisp
Well-Known Member
Also, does that look like enough of a blockage to be causing power loss? She was definitely under-powered at the end of the season...
dankilb
Well-Known Member
(Aerosol/spray) oven cleaner is good - but only on bits you can remove and clean properly.
garymalmgren
Well-Known Member
RE; what do I do? Chip it out? How?
For the parts that you can remove, oven cleaner seems to work to remove carbon or at least soften it.
Re+ does that look like enough of a blockage to be causing power loss?
Carbon build up will effect exhaust gas flow and make the engine sluggish.
gary
how to disolve carbon build up - Bing video
For the parts that you can remove, oven cleaner seems to work to remove carbon or at least soften it.
Re+ does that look like enough of a blockage to be causing power loss?
Carbon build up will effect exhaust gas flow and make the engine sluggish.
gary
how to disolve carbon build up - Bing video
Laysula
Well-Known Member
If your going to do it in place, then push a wad of rag tied to a piece of string as far down as you can and then when you have finished draw it out with the string and you should then bring any debris out with it.
AntarcticPilot
Well-Known Member
+1. But it would be much easier to do if you can get the manifold off.; you really don't want bits of crud dropping into the cylinders or getting into the valve gear. The workshop manual will be a great help. On mine (Volvo Penta 2003), the exhaust manifold is part of the cylinder head, so you have to get a gasket kit to do that.
Daydream believer
Well-Known Member
I tried chipping the carbon from a discarded exhaust elbow to keep as a spare. Within minutes I cracked the casting. I suggest that one might look at something like a Dremel with a grinding attachment of some sort, rather than something involving impact. Perhaps one of those drill bits for enlarging holes at an angle shaped like a sherbert on a stick.
Certainly do not try hammering on an expensive component like a manifold.
The carbon deposit was rock hard. I tried a strong solution of Hydrochloric acid, as I had some that I had obtained commercially years ago & it did nothing. If forumites know of a chemical remedy, that actually works & is easily obtainable, then I suggest that might be the way to go.
Certainly do not try hammering on an expensive component like a manifold.
The carbon deposit was rock hard. I tried a strong solution of Hydrochloric acid, as I had some that I had obtained commercially years ago & it did nothing. If forumites know of a chemical remedy, that actually works & is easily obtainable, then I suggest that might be the way to go.
AntarcticPilot
Well-Known Member
Given the location in the manifold rather than the elbow, the deposit is probably almost pure carbon. I'd give a blow torch a go and see if it could be burnt off. If not, chipping and chiseling is the only way; carbon is insoluble in almost everything.
Deposits in exhaust elbows are a different kettle of fish, as they'll include salts from the seawater injection, with too low a carbon content for burning to work. When I cleaned my exhaust elbow, mechanical cleaning was all that worked.
Unfortunately, there are no solvents that would be certain to shift these deposits. Acid MIGHT help on an exhaust elbow (but it didn't on mine, and I left it soaking overnight)
Captain Crisp
Well-Known Member
Now wondering if it's not as bad as I thought... looking at an online image, you can see that the exhaust tapers down to the oval shape, so it's not all carbon as I previously thought... does this look enough of a blockage to have seriously affected performance? Given that the elbow was completely clear... Perhaps it was just a blocked filter?
Neeves
Well-Known Member
I had an elbow that accumulated deposit until the hole was the size of a pencil. The engine ran fine until that point - so the deposit you have is not likely to be the cause of the engine being sluggish. The latter might simply be due to a fouled prop. I have found concentrated acid to work on an elbow, once only. The second time the acid concentrations are sufficient to corrode the diverter within the elbow (probably because has corroded and its the iron oxide that dissolves rather than the metal). As mentioned carbon is inert and a blow torch might work - I would not use a hammer and chisel for the reasons mentioned. The deposits in the elbows is a mix of carbon and precipitated calcium salts and its the calcium that is dissolved, rather then the carbon, but the calcium salts hold the carbon and as it all looks black - everyone assumes its solid carbon. You do need to use concentrated acid - and have a method of disposal afterwards.
You can buy rasps that fit into a conventional hand drill. Whether they are long enough to get into the manifold - don't know. A Dremel is a bit wimpy - you would need a lot of patience. I'd use the tie the rag trick (see above) and run a vacuum cleaner at the same time as trying to abrade - but I don't think the build up is the cause of the engine being sluggish.
As an side - I have a suspicion precipitated calcium from seawater varies around the world, I believe in the Gulf of Mexico there are high concentrations (and maybe the Red Sea). In some places the concentrations are so high the calcium precipitates out as a continual process, building up new limestone beds. Possibly also high around limestone and chalk coastlines - Dover? compared with the Western Isles of Scotland. The problems may be partially regional.
Why stainless elbows appear better than cast elbows is a bit of a mystery.
Jonathan
You can buy rasps that fit into a conventional hand drill. Whether they are long enough to get into the manifold - don't know. A Dremel is a bit wimpy - you would need a lot of patience. I'd use the tie the rag trick (see above) and run a vacuum cleaner at the same time as trying to abrade - but I don't think the build up is the cause of the engine being sluggish.
As an side - I have a suspicion precipitated calcium from seawater varies around the world, I believe in the Gulf of Mexico there are high concentrations (and maybe the Red Sea). In some places the concentrations are so high the calcium precipitates out as a continual process, building up new limestone beds. Possibly also high around limestone and chalk coastlines - Dover? compared with the Western Isles of Scotland. The problems may be partially regional.
Why stainless elbows appear better than cast elbows is a bit of a mystery.
Jonathan
QBhoy
Well-Known Member
Good to give her a good workout every now and then. Check you aren’t running cold too. Bad thermostat and running cold can cause this too. Other thing that might also cause this is a weeping injector or two. More likely one or both of the former though.
AntarcticPilot
Well-Known Member
Oolitic limestone (as in the Jurassic limestone that extends from Yorkshire down to the Jurassic Coast of Dorset) is calcium carbonate chemically precipitated from seawater. The process is happening today in places like the Bahama Banks - shallow seas with high evaporation rates. There may be a biological aspect as well.
I think it's unlikely that the presence of limestone rocks at sea shores would have much effect except on a very local scale. Rivers running over limestone might have a greater but still local effect. But the fact that it doesn't take much to precipitate calcium carbonate from sea water suggests that it is already fairly saturated with respect to carbonate, and the variation may well be down to temperature variations altering the solubility of calcium carbonate. Calcium carbonate has very low solubility.
Neeves
Well-Known Member
Maintaining the thread drift.
I may well be incorrect in suggesting that the blockage in the exhaust elbow is carbon bonded with a salt of calcium. Apparently a typical analysis of seawater contains 1272 ppm of Magnesium and only 400 ppm of calcium - suggesting that magnesium may be the bonding agent. For decades the high levels of dissolved magnesium in seawater resulted in extraction as a tonnage process of the Mg at Hartlepool (as MgOH or MgO). There were similar plants using the same process in a variety of locations round the world.
Both as carbonates are soluble in a variety of acids - so whether it is calcium or magnesium does not really matter.
Jonathan
I may well be incorrect in suggesting that the blockage in the exhaust elbow is carbon bonded with a salt of calcium. Apparently a typical analysis of seawater contains 1272 ppm of Magnesium and only 400 ppm of calcium - suggesting that magnesium may be the bonding agent. For decades the high levels of dissolved magnesium in seawater resulted in extraction as a tonnage process of the Mg at Hartlepool (as MgOH or MgO). There were similar plants using the same process in a variety of locations round the world.
Both as carbonates are soluble in a variety of acids - so whether it is calcium or magnesium does not really matter.
Jonathan
geem
Well-Known Member
I have decoked cast iron exhaust elbows with a Dremel. Worked well.
AntarcticPilot
Well-Known Member
Not so sure. Of course you're right about the relative concentrations, but it is also fact that calcium carbonate precipitates out of seawater before magnesium carbonate, though there is a degree of co-precipitation. I think that calcium carbonate is less soluble than magnesium carbonate. But in places where carbonates are being deposited from seawater (e.g. the Bahama Banks) it is mainly calcite and aragonite being deposited, not dolomite.
However, and bringing it back to practicalities, you're quite right that both dissolve in acid, provided the salts formed are soluble - sulphuric acid won't work because calcium and magnesium sulphate are insoluble; hydrochloric acid is good (the standard field test for carbonate rocks uses hydrochloric acid). Nitric acid would also work, but might dissolve the iron a bit too enthusiastically!
