Ships_Cat
Well-Known Member
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Diesel disaster - help!
- Thread starter roberth
- Start date
PeterGibbs
Well-Known Member
Most promising areas for investigation are:
1. sump oil - check carefully if there is any discolouration or tendency to clump as "black butter". This signals water in the oil and is serious - failure to remove (sea) water will result in highly damaging corrosion. Very costly if not attended to immediately - use flushing oil and turn over by hand to circulate, then pump out. Engage decompressors if fitted, otherwise loosen injectors and shut off diesel supply to engine. Avoid even trying to run engine until cause of water ingress known and fixed.
2. Cause of the above is likely to be failure of head gaskit. Romoval of rocker top and strip down to replace gaskit is a DIY job for the initiated. Otherwise it's time to summon your friendly engineer!!
PS. If using an engineer, try to be there when the top comes off - next time you'll be confident to do it yourself!
PWG
1. sump oil - check carefully if there is any discolouration or tendency to clump as "black butter". This signals water in the oil and is serious - failure to remove (sea) water will result in highly damaging corrosion. Very costly if not attended to immediately - use flushing oil and turn over by hand to circulate, then pump out. Engage decompressors if fitted, otherwise loosen injectors and shut off diesel supply to engine. Avoid even trying to run engine until cause of water ingress known and fixed.
2. Cause of the above is likely to be failure of head gaskit. Romoval of rocker top and strip down to replace gaskit is a DIY job for the initiated. Otherwise it's time to summon your friendly engineer!!
PS. If using an engineer, try to be there when the top comes off - next time you'll be confident to do it yourself!
PWG
AndrewD
Active Member
If it does turn out to be full of water, check your stern seal arrangements. Do you have a mech. seal ("Deep Sea Seal" or similar) or a gland? If the former, how is it lubricated? If it's a bleed off the cooling water, they can be mis-installed (by professionals!) and allow water back into the engine under certain circumstances of heel etc. I nearly lost my engine this way.
If you have a conventional stern gland, none of the above applies.
If you have a conventional stern gland, none of the above applies.
Avocet
Well-Known Member
Sorry to hear about your plight!
If it's any consolation, We had precisely the same thing happen to us some years ago! We have a little BMW D12 single cylinder raw water cooled engine. Like you, the engine was running fine, was left (seacock closed) for a few weeks and then acted as it it was siezed. That's because it WAS!
I took the head off and there was 1/4" of salt water on top of the piston! The rings were rusted to the bore. No amount of hammering would persuade it to budge. In the end I had to take the big end bearing off and take the barrel (with the piston in it) back home...
...One second hand piston (and barrel) later -and some new rings!, I got it all back together and it has been fine ever since.
I never really got to the bottom of why it happened. I'm pretty certain the little air vent in the top of the anti-syphon valve was blocked and the engine just happened to stop with the exhaust valve open that day. I replaced the valve with one of those Vetus ones that has a pipe leading overboard from the vent. It provides a tell-tale when the engine is running and, by virtue of its design, is pretty impossible to block.
I also noticed a small pin hole in the exhaust elbow (inside the casting) that was blocked. I haven't quite worked out exactly what this is for but I think it is another measure to stop water going back up the exhaust port. Maybe your engine has something similar?
The only bit of good news I can give is that none of the water had made it past the rings and into the engine's bottom half.
If it's any consolation, We had precisely the same thing happen to us some years ago! We have a little BMW D12 single cylinder raw water cooled engine. Like you, the engine was running fine, was left (seacock closed) for a few weeks and then acted as it it was siezed. That's because it WAS!
I took the head off and there was 1/4" of salt water on top of the piston! The rings were rusted to the bore. No amount of hammering would persuade it to budge. In the end I had to take the big end bearing off and take the barrel (with the piston in it) back home...
...One second hand piston (and barrel) later -and some new rings!, I got it all back together and it has been fine ever since.
I never really got to the bottom of why it happened. I'm pretty certain the little air vent in the top of the anti-syphon valve was blocked and the engine just happened to stop with the exhaust valve open that day. I replaced the valve with one of those Vetus ones that has a pipe leading overboard from the vent. It provides a tell-tale when the engine is running and, by virtue of its design, is pretty impossible to block.
I also noticed a small pin hole in the exhaust elbow (inside the casting) that was blocked. I haven't quite worked out exactly what this is for but I think it is another measure to stop water going back up the exhaust port. Maybe your engine has something similar?
The only bit of good news I can give is that none of the water had made it past the rings and into the engine's bottom half.
paulwitney
Active Member
Had similar problem with my last boat and an arona single cylinder engine. Exhaust elbow corroded and cylinder filled with salt water. It did start though but with a bang!!! that sounded like the motor had gone through the hull!! (Water doesn't compress.) Sump and everywhere else had oil that looked like brown butter. Much flushing with kerosene and then new oil and of course fix of the exhaust elbow and the motor is still going strong 8 years later. As others said check for "butter" oil or release compression and turn engine over to remove water but IF there was water find out where it came from!!!!!!!
PuffTheMagicDragon
Well-Known Member
[ QUOTE ]
I also noticed a small pin hole in the exhaust elbow (inside the casting) that was blocked. I haven't quite worked out exactly what this is for but I think it is another measure to stop water going back up the exhaust port. Maybe your engine has something similar?
[/ QUOTE ]
Are you sure that the hole was intentional and that itself was not the cause of the failure?
I had an engine where the gasket between the heat exchanger and the exhaust elbow failed. This allowed the water from the exhaust line to slosh back up the pipe towards the manifold as soon as the engine was turned off and therefore there was no more pressure. The Vetus water trap was too small for the volume that came back down the rising part of the exhaust.
I traced the problem down to a slightly bowed flange to the exhaust elbow (welded stainless tube). This was not sealing properly and the leaking exhaust soon caused the gasket to fail - together with a good bit of aluminium alloy.
Solution was :
(1) rebuild the metal of the manifold and machine.
(2) dress the elbow flange to a flat state.
(This ensured that there was a good seal with the gasket.)
(3) install a swan neck just after the water trap so that the volume of the up-going part of the tube is much less than the capacity of the water trap.
Problem solved (touching wood, crossing fingers and legs while offering sacrifices to the sea gods!)
Might be worth checking.
I also noticed a small pin hole in the exhaust elbow (inside the casting) that was blocked. I haven't quite worked out exactly what this is for but I think it is another measure to stop water going back up the exhaust port. Maybe your engine has something similar?
[/ QUOTE ]
Are you sure that the hole was intentional and that itself was not the cause of the failure?
I had an engine where the gasket between the heat exchanger and the exhaust elbow failed. This allowed the water from the exhaust line to slosh back up the pipe towards the manifold as soon as the engine was turned off and therefore there was no more pressure. The Vetus water trap was too small for the volume that came back down the rising part of the exhaust.
I traced the problem down to a slightly bowed flange to the exhaust elbow (welded stainless tube). This was not sealing properly and the leaking exhaust soon caused the gasket to fail - together with a good bit of aluminium alloy.
Solution was :
(1) rebuild the metal of the manifold and machine.
(2) dress the elbow flange to a flat state.
(This ensured that there was a good seal with the gasket.)
(3) install a swan neck just after the water trap so that the volume of the up-going part of the tube is much less than the capacity of the water trap.
Problem solved (touching wood, crossing fingers and legs while offering sacrifices to the sea gods!)
Might be worth checking.
Avocet
Well-Known Member
Yes, quite sure. Corrosion wasn't an issue on this occasion. it was a neat little (approx) 3mm hole (no idea what it was for!) but it was blocked with soot mainly, rather than rust or salt.