Lost without a clue: Saltwater in oil

[pbmaise]

We have been trying to figure out how saltwater is getting into our engine and run out of ideas.

Isuzu 6BD1 engine.

We removed the coolant/saltwater exchanger and took it to a shop for testing. No leaks. Excellent condition.

We removed the coolant/oil exchanger and it was fine too.

A taste test of water in the oil pan = saltwater
A taste test of engine coolant = no salt
Transmission fluid fine.

One possible clue we thought was the slow loss of coolant before this occurred. The boat is run commercially now which mean I am not their to oversee it all the time. The mechanic installed a gravity fed reservoir to the radiator. One strange guess I have is someone refilled that reservoir with saltwater instead of fresh.

However, I insisted on removing the reservoir and salt water got into the engine oil yet again.

I just purchased a complete head gasket kit since I thought the problem was coolant mixing into the oil. I am now concerned installing it would be wasted effort. We have no smoke issues with the engine and it sounds fine.

I had saltwater in the engine before, however, that was almost 12 years ago while crossing the Pacific in rough weather. I am still not sure if that saltwater came up the exhaust or through saltwater supply line to the engine which was open. I was paranoid after that and would close the saltwater supply line even at the dock. That was fine while it was only myself starting the engine since I could be certain to open the supply line before starting the engine.

I never had saltwater in the engine since I began closing the supply line, however, I also have not been crossing the Pacific either.

The engine is mostly above the waterline. The saltwater mixing elbow is above the waterline too. This said, the oil pan is below it.

Given the commercial crew, I really worry about telling them to begin closing that supply line each time they shut the engine off. They could do a lot of damage if they forgot to open it if they were in a hurry.

The vessel has not been in any rough water for over 2 years.

I hope this is enough information for someone to give me a clue as to what to do. My only thought is to review the current procedure of opening and closing that saltwater supply line despite the fact I doubt it is the problem.

[Minggat]

For your concern about commercial crew, understood. If you get them to store the key on the closed valve handle when done running the engine, that has worked for me.

A friend rebuilt his engine twice before finding the problem. No guarantee that this is yours. Water in the line from the exhaust pot to the thru hull was coming back down the hose and into his engine.

[jimbunyard]

Do you have a gear-driven raw water pump? If so, a failed or failing water seal on the pump can allow water to be sucked into the engine even if the oil seal on the pump is fine.

An example:

https://www.cruisersforum.com/forums...ch-229225.html

[pbmaise]

Jim...Very good question about gear driven pump. No it is belt.

Ming...Thank you for your post. I am keenly interested to know you knew someone who experienced back flow from the exhaust system after engine shutdown.

I was probably a bit embarrassed to fully admit the strange thing I was doing during engine shut down. I came up with the idea to continue running the engine for a few seconds after shutting off the saltwater supply before pressing the kill switch. I figured I was flushing water out of the muffler tank.

I did not train the crew operating the vessel to do this same procedure and this could be the only source of saltwater into the engine.

If the new shut down sequence is...

1. Raw water valve closed
2. Wait five seconds
3. Shut down engine
4. Open raw water valve

With this sequence, the raw water valve will be open and ready to go the next time someone starts engine. Since the vessel now operates in quite calm waters compared to where I used to sail, I am in calm waters I am confident that the raw water valve can remain open while the engine is shut down.

Yes, shutting off the water supply to the pump is probably hard on the impeller and belt, however, we have gone through almost 60 liters of oil that had to be tossed owing to this problem.

I am just curious if anyone has heard of someone with such an odd engine shut down sequence.

I frequently think the strange things I do on my boat are unique only to find out that other sailors have solved the same problem in a similar way.

[a64pilot]

It’s I believe very uncommon for salt water to enter the oil through the exhaust and not cause any harm to the engine.
Most discover salt water is getting in from a hydrolock or other engine damage like rings seized from rust etc.

I believe this is one of those times that an oil analysis is called for, they should be able to determine for sure it’s salt water from the sodium content, and I believe can confirm or deny it being coolant.
There are also inexpensive test kits to determine if combustion gases are present in the coolant, which pretty much means a bad head gasket.

I’m thinking your slow loss of coolant is related, and it may be a head gasket after all.

[Bill O]

Did the motor ever over heat before you noticed the saltwater in the oil?

Would agree w/ A64 if it came back through the exhaust, the motor would hydrolock and not just put water into the oil pan.

If in fact it did over heat, would check/replace the head gasket or worst case suspect a crack in the block.


Edit: Does the oil look like a milk shake?

[SVHarmonie]

I have nothing definative, just some ideas, and need some more information...I know some of these questions will seem annoying, but these are the kinds of things I would look for if I was there:

When you say "in the engine" I assume you mean in the oil. Is there evidence of water anywhere else? Is there enough water to measurably raise the oil level?

After an oil change how quickly does water appear?

You say your exhaust elbow is "above the water line," How high? and is there an additional loop in the exhaust line above that? Is there a syphon break anywhere in the system? Does the exhaust line dip below the water line anywhere at all? How old is the exhaust elbow? When was the last time it was removed?

Does the exhaust leave the hull out the side, out the back?

I assume you have a water lock muffler. Have you looked to see if it is full?

How much sailing is done compared to motoring? Water making its way back into the exhaust while the engine is running is ALMOST impossible.

Are you still loosing coolant? Can you pressure test the coolant system? The taste test isn't always definitive... Don't assume the head gasket is the only place for coolant to disappear. There are usually gaskets in the exhaust manifold jacket that separate coolant from exhaust that can fail too...

[Minggat]

Originally Posted by pbmaise

Jim...Very good question about gear driven pump. No it is belt.

Ming...Thank you for your post. I am keenly interested to know you knew someone who experienced back flow from the exhaust system after engine shutdown.

I was probably a bit embarrassed to fully admit the strange thing I was doing during engine shut down. I came up with the idea to continue running the engine for a few seconds after shutting off the saltwater supply before pressing the kill switch. I figured I was flushing water out of the muffler tank.

I am just curious if anyone has heard of someone with such an odd engine shut down sequence.

I frequently think the strange things I do on my boat are unique only to find out that other sailors have solved the same problem in a similar way.

I’ve put the question to my friend to find out if I got it right.

Ok, I’ll agree that your shut down procedure seems... not normal.

I will say that I believe you’re worried about the wrong thing regarding the re-opening of your cooling water seacock. More boats sink in their slips than at sea due to through hull valve that should be closed when the boat is unoccupied.

Not sure what you’re asking about my friends problem. As I recall, it was a long run of hose that held enough water to be the problem. He put the exhaust outlet closer with a new through hull. Problem solved.

[jamhass]

Originally Posted by SVHarmonie

Is there a syphon break anywhere in the system?

Is the water-lift muffler higher or lower than the engine?

[lookinggoodrock]

Is the exhaust manifold / heat exchanger water cooled. My yanmar had salt water backing into engine because exhaust eventually burned a hole in manifold. Thereby saltwater backing in through exhaust vaves. Mine was so bad it created hydraulic lock on cylinder. If yours is just a pinhole it may be getting past the rings into sump?

[SVHarmonie]

Originally Posted by pbmaise

I was probably a bit embarrassed to fully admit the strange thing I was doing during engine shut down. I came up with the idea to continue running the engine for a few seconds after shutting off the saltwater supply before pressing the kill switch. I figured I was flushing water out of the muffler tank.

I would definitely NOT do this.

First, IF it is necessary, then there is a basic design flaw in the exhaust system that needs to be fixed.

Second, it is really tough on your raw water impeller.

Third, maybe 5 seconds doesn't matter, BUT the temperature in the wet part of your exhaust system will rise REALLY fast without water flow to the point of seriously damaging hoses and mufflers and other parts that are not designed for the 1000 degree plus temperatures of dry diesel exhaust.

Again, if this weird procedure is NECESSARY to prevent a problem then FIX the problem.

[SVHarmonie]

Originally Posted by Bill O

Would agree w/ A64 if it came back through the exhaust, the motor would hydrolock and not just put water into the oil pan.

While this is USUALLY true, I can assure you it is not ALWAYS true. It depends on lots of things. But an engine can certainly get a small amount of water in through the exhaust and not "lock up".

[capn_billl]

There are only a few options.

1. crack or rust in exhaust elbow. Just had this issue myself.

2. Bad shaft seal.

3. hole in oil pan.

4. you've already eliminated heat exchanger, but I'd continue looking closely at it.

[roverhi]

Gear driven coolant pump. When they fail they leak coolant into the oil passage for the gear drive. Are you sure it's salt water??

[Niall leslie]

I worked on two of those engines decades ago but in fresh water lakes.
If the sea water getting into the engine lubricating oil is a reasonably high amount and is not being added maliciously then the sea water entry can only take place at a point where the sea water and engine oil can mix and at a point where the oil pressure is lower than the sea water pressure.
Coolers and heat exchangers, intercoolers etc., raw water pumps, any parts of the engine system cooled by sea water would be the usual possibilities.
I also once encountered a case where a pinhole leak in a pressurized hose from the raw water pump was allowing raw water to get into the dipstick tube when the engine was running hard!
Good luck,
Niall.