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Old 26-08-2016, 02:05   #1
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How is this Possible?

We have a Yanmar 100hp turbo diesel and a Westerbeke 10kw genset, each is running just fine. We had the shipyard clean out both heat exchangers last winter in off-season. Both systems then run through an exhaust separator so the water from the exhaust comes out below the waterline and the diesel exhaust above the waterline.

Here's what I can't figure out.... When I run the generator, more and more coolant builds up inside the Yanmar engine then drips out via the coolant overflow chamber. When the Yanmar engine runs by itself... No problem, the Yanmar coolant level remains constant. When I run the generator, the coolant level in the engine rises then overflows, drip, drip, drip. Somewhere, water is being added to the coolant system and is then dripping out via the Yanmar overflow chamber.

I can't understand where the water is coming from, any help will be appreciated.

Neither engine is running hot or overheating when this takes place. The Westerbeke overflow chamber remains at a constant level.

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Old 26-08-2016, 02:55   #2
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Re: How is this Possible?

Quote:
Originally Posted by Kenomac View Post
We have a Yanmar 100hp turbo diesel and a Westerbeke 10kw genset, each is running just fine. We had the shipyard clean out both heat exchangers last winter in off-season. Both systems then run through an exhaust separator so the water from the exhaust comes out below the waterline and the diesel exhaust above the waterline.

Here's what I can't figure out.... When I run the generator, more and more coolant builds up inside the Yanmar engine then drips out via the coolant overflow chamber. When the Yanmar engine runs by itself... No problem, the Yanmar coolant level remains constant. When I run the generator, the coolant level in the engine rises then overflows, drip, drip, drip. Somewhere, water is being added to the coolant system and is then dripping out via the Yanmar overflow chamber.

I can't understand where the water is coming from, any help will be appreciated.

Neither engine is running hot or overheating when this takes place. The Westerbeke overflow chamber remains at a constant level.
If the only point of mutuality in terms of water is the exhaust separator, then somehow the water is syphoning back into the Yanmar. Try leaving the lid off the the Yanmar overflow chamber whilst running the generator. Smell the water in the overflow tanks and see if it smells diesel... and feel it if is greasy. Other than that, disconnect the generator from the exhaust separator and see..
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Old 26-08-2016, 03:04   #3
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Re: How is this Possible?

If the exhaust systems are interconnected, my guess is that the exhaust pressure from the running generator is feeding back into the raw water side of the Yanmar, and an improperly sealed heat exchanger is allowing sea water to be pushed back into the freshwater side, overfilling the overflow tank.

That of course leaves the question 'why isn't the same thing happening when the Yanmar is running?' It could be, but either the cap pressure is enough to contain it, or the heat from the engine and pressure from the freshwater pump are enough to contain it or any combination of the three could combine to stop it.

One sure sign would be that you have salt water in the fresh water side of the Yanmar.

Of course it could be something completely different, without a schematic showing how both are set up, troubleshooting is pretty much guesswork...
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Old 26-08-2016, 03:21   #4
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Re: How is this Possible?

The two engines do not share a common heat exchanger or water separator. This is a genuine mystery.
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Old 26-08-2016, 03:22   #5
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Re: How is this Possible?

check the cap and make sure it is the correct pressure and if in doubt change it

does the engine require topping up at all when its cold and the generator has not been running?.

the extra water is either the water in the system is expanding from heat or something has been changed or failed to add the water. ( piped or a damaged seal)

do you expect its salt water getting into the system, if you do test the coolant for salt with a meter if you have a water maker you will have one?
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Old 26-08-2016, 03:32   #6
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Re: How is this Possible?

After some more testing, it appears the engine heat exchanger is the problem. When I brought the Yanmar engine up to temp, the drip increased dramatically.

Now the question is, can I wait three weeks to get the heat exchanger repaired by the folks who did the work last winter? Is the small amount of seawater circulating through the engine a problem over this time period? It drips one drop every two seconds.
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Old 26-08-2016, 03:39   #7
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Re: How is this Possible?

A drip every 2 seconds will fill a bathtub in 24 hours
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Old 26-08-2016, 04:00   #8
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Re: How is this Possible?

Get a hygrometer and measure the glycol content of the coolant, or a TDS meter to look for salt, or taste it. Measure against a control. I presume the coolant level in effect keeps on being added to if the header tank overflows, so sea water must be getting in. It is essential to verify that. If you are sure it is happening then a pressure test of the heat exchanger and repair or replace is next. You may also block of the faulty tube if you can find it. A pair of machine screws will be a quick and dirty fix. Also get a coolant flush.

Maybe the vibration of the genset is inducing some kind of pump action and an imperfect seal on the cap allows fluid to pass.

Sea water in the coolant will spoil your engine and a hole in the heat exchanger will cause the motor to overheat as the coolant goes out when hot and pressurised.
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Old 26-08-2016, 04:03   #9
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Re: How is this Possible?

Too many variables to know for sure. If I had the materials and the ability I'd repair it now, the system is designed to run with antifreeze and freshwater, any aluminum in the F/W side might be compromised after 3 weeks.


That being said, I ran my MD2020 for about 6 months with a similar 'mixing' problem with no (apparent) ill affects, but that's more of a basic old school engine...
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Old 26-08-2016, 05:13   #10
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Re: How is this Possible?

The Yanmar is well bonded to the giant anode, I've passed along the information and video to the folks who did the heat exchanger work, and now waiting back for their recommendation. I'm only 300 miles away and a coolant flush and winterization was already previously scheduled.
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Old 26-08-2016, 05:40   #11
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Re: How is this Possible?

I am sure your cap is bad, or the pressure is going above 13 psi to allow coolant past the cap but in this case it alerted you to another problem. Although I would not want salt water in my engine the same basic engine is used in a raw water version I would run it but do a flush after heat exchange repair
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Old 26-08-2016, 09:48   #12
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Re: How is this Possible?

From your description of it being coolant. I am afraid you have a pinhole in the heat exchanger core of your main engine. Without the main raw water pump running the gen. raw water is putting a little pressure on the raw water side of the main forcing a little raw water into the coolant.
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Old 26-08-2016, 09:54   #13
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Re: How is this Possible?

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Originally Posted by Cadence View Post
From your description of it being coolant. I am afraid you have a pinhole in the heat exchanger core of your main engine. Without the main raw water pump running the gen. raw water is putting a little pressure on the raw water side of the main forcing a little raw water into the coolant.
Thanks, this is exactly the same conclusion I came to earlier today after I ran the Yanmar engine for twenty minutes and watched the drip dramatically increase. I'm now just waiting for advice from the shipyard which serviced the heat exchanger. Wondering now whether it's OK to continue 300 miles further north to haul out at their yard.

Thanks again.

Ken
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Old 26-08-2016, 09:55   #14
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Re: How is this Possible?

I bet they reused an o-ring and it is as simple as a leaking o-ring in the heat exchanger


Even if you were running pure salt water in the fresh water side, so long as it was just a few days and you flushed it well, it's not going to kill anything. It's time that the salt is left in the system that will do the damage, not running time, but calendar time.
a simple pressure test should tell the tale
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Old 26-08-2016, 10:15   #15
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Re: How is this Possible?

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I bet they reused an o-ring and it is as simple as a leaking o-ring in the heat exchanger


Even if you were running pure salt water in the fresh water side, so long as it was just a few days and you flushed it well, it's not going to kill anything. It's time that the salt is left in the system that will do the damage, not running time, but calendar time.
a simple pressure test should tell the tale
Right now, the coolant is still deep bright green antifreeze, but it'll be three weeks till we arrive at the shipyard.
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