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Old 10-02-2022, 10:19 AM   #1
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My Northern Lights Genset Overheats.

Before leaving on this trip a trip to the Ontario North Channel, I checked it over and started it and ran it five minutes. The reservoir was topped off with 50-50, it had a newly installed seawater impeller which sprayed water out into the lake like a firehose. Nothing that I could see had changed since the past season. It had been flushed out with two gallons of -60 blue pop for winterization and had a block full of 50-50 Prestone. All was well.

After running the genset to power the AC for about an hour on the only hot day all summer in the North Channel, she shut down. The panel does not have a temp gauge, but the engine obviously does the right thing and shuts down at some point to save its own soul. There was a significant amount of 50-50 in the pan after the episode. I refilled the reservoir and it took about 8 oz to top it off to about half an inch below the cap as recommended by the manufacturer. There is a little bell-shaped thing in the hole under the cap and it is recommended to fill up to the bottom of that little gadget.

Recently, while going through the boat after returning to Detroit area, I checked the genset and it had not lost any coolant since the overheating episode and refilling. In the meantime, I had put on a new coolant cap, 7psi, ordered from the NL dealer just to eliminate that as a problem. I started it and let it run about 10 minutes with the AC on the Heat mode to load the engine and it started well and ran well, but after shutting down, I found a few tablespoons of 50-50 in the pan. I could feel the coolant was down perhaps a half inch in the reservoir.

I carefully looked at the engine and conclude that the coolant is coming from the back side which is very inaccessible. It was leaking out and running forwards under the engine towards the service side. It sits crosswise in the very back end of the engine room of my GB 32 and it is almost impossible to see the back side of the engine. Using my flexible scope, I could see some staining on the back side but was not really able to pin it down to a specific area. Summary: loses 50-50 from engine while running only, as far as I can tell. What's up?
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Old 10-02-2022, 01:36 PM   #2
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I had a problem in a prior boat with genset overheating. Checked all the obvious items, changed impeller, outflow seawater was strong. Have you checked the temp of the exhaust water? If it is not at least a bit warm after 15 minutes you have probably have an issue with either the heat exchanger or the freshwater cooling pump. My problem was the pump. Flow was apparently weak or non existent so while the exhaust water was vigorous it was not transferring heat from the freshwater to the seawater. Hope this helps.
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Old 10-02-2022, 02:50 PM   #3
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Pressure test the cooling system. You can borrow a pressure tester from many auto parts stores. Advanced Auto Parts for one. But before that double ck that the radiator cap is fully locked on. Also double ck to be sure that a 7lb cap is correct for that application. Does the generator have an overflow bottle? If so what is the status of the level in the bottle? If it doesn't have an overflow bottle I would add one. Is the alternator belt tight? Not slipping on the coolant pump pully? Start with the basics.
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Old 10-02-2022, 03:09 PM   #4
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The engine shutting down, presumably on overheat, and losing coolant are no doubt related. First shoot the thermostat housing with an IR gun with the engine running and under load to get an idea of degree of overheat. Should be no more than 200 F.

There are three areas that I would look into:

1.The raw water heat exchanger being scaled up causing the overheat and coolant blowing out. But in this case it would blow by the "radiator" cap and not out some unlikely place at the back side of the engine.

So, remove the end caps on the heat exchanger and rod the tubes with a .22 rifle cleaning rod and then circulate Barnacle Buster or similar to remove the scale.

2. A coolant leak somewhere on the back side of the engine. You can buy a dye that will make it easier to see where it is leaking.

3. A bad head gasket or worse a crack in the head letting combustion gasses into the coolant. Once enough coolant has been blown out, the engine overheats and shuts down.

This is easily tested by filling up the coolant, running the engine until warm and looking in the filler port. If you see bubbles, it is probably exhaust gas leakage.

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Old 10-02-2022, 03:19 PM   #5
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Quote:
Originally Posted by grandbanksbayfield View Post
Before leaving on this trip a trip to the Ontario North Channel, I checked it over and started it and ran it five minutes. The reservoir was topped off with 50-50, it had a newly installed seawater impeller which sprayed water out into the lake like a firehose. Nothing that I could see had changed since the past season. It had been flushed out with two gallons of -60 blue pop for winterization and had a block full of 50-50 Prestone. All was well.



After running the genset to power the AC for about an hour on the only hot day all summer in the North Channel, she shut down. The panel does not have a temp gauge, but the engine obviously does the right thing and shuts down at some point to save its own soul. There was a significant amount of 50-50 in the pan after the episode. I refilled the reservoir and it took about 8 oz to top it off to about half an inch below the cap as recommended by the manufacturer. There is a little bell-shaped thing in the hole under the cap and it is recommended to fill up to the bottom of that little gadget.



Recently, while going through the boat after returning to Detroit area, I checked the genset and it had not lost any coolant since the overheating episode and refilling. In the meantime, I had put on a new coolant cap, 7psi, ordered from the NL dealer just to eliminate that as a problem. I started it and let it run about 10 minutes with the AC on the Heat mode to load the engine and it started well and ran well, but after shutting down, I found a few tablespoons of 50-50 in the pan. I could feel the coolant was down perhaps a half inch in the reservoir.



I carefully looked at the engine and conclude that the coolant is coming from the back side which is very inaccessible. It was leaking out and running forwards under the engine towards the service side. It sits crosswise in the very back end of the engine room of my GB 32 and it is almost impossible to see the back side of the engine. Using my flexible scope, I could see some staining on the back side but was not really able to pin it down to a specific area. Summary: loses 50-50 from engine while running only, as far as I can tell. What's up?


I would suggest you also pull out the thermostat and test it. A thermostat not opening would fit your observations
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Old 10-02-2022, 06:33 PM   #6
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If you have a coolant leak you have to fix that. There is ultraviolet dye you can add to the coolant and check with a UV flashlight to find the source of the leak. Talk to an auto parts dealer to hook you up with UV leak detection stuff.
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Old 10-02-2022, 07:11 PM   #7
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I would suggest you also pull out the thermostat and test it. A thermostat not opening would fit your observations


Assuming you have confirmed it is actually overheating, then the coolant is likely expanding past the cap or the reservoir. It is not overheating due to coolant loss, so fix the overheating and the coolant overflow will likely stop.
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Old 10-05-2022, 11:50 AM   #8
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Check your overflow line from under the radiator cap to the expansion tank. On my westerbeke it is a fitting just beneath the fill neck where the pressure cap goes on. Mine was clogged, so removed the fitting and used a small drill bit to open the small hole behind the fitting into the filler neck. That took a while to figure out. One other place I developed a leak was the engine coolant pump. It was pretty subtle and the pump didn't make any noise. The dye sounds like a good idea. Murphy's law is that the leak is on the inaccessible side
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Old 10-05-2022, 07:40 PM   #9
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Don’t know the model you have but on the 5kw 673 you need to Check the rubber boots on the heat exchanger. Raw water and coolant flow through the heat exchanger with raw water on the inside and coolant on the outside. There are two hose clamps one, keeping the raw water from mixing with coolant and the other keeping the coolant contained. Need to check them for tightness of the clamps.

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Old 10-10-2022, 12:55 PM   #10
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More than likely you have a problem in the head, we had a similar issue that was slowly using antifreeze and overheating and shutting down after about an hour...no sign of water in the oil then it finally gave out and the oil was full of water. pulled the head and sent it in for rebuild and they found the problem was a interior frost plug that had a small corrosion hole thru it ( 1/8). I replaced the injectors, new glow plugs, boiled the heat exchanger out etc it now runs better than ever. This was on a 12 kw NL.
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Old 10-10-2022, 01:20 PM   #11
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I have this leak detector kit for Amazon.

MASTERCOOL 53351-B Professional UV Leak Detector Kit with 50W Mini Light, Black
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Old 10-10-2022, 07:33 PM   #12
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Genset overheating

Thanks so much for the great replies. It gave me a good sense of direction. In any case, I am pretty sure we will have to pull the engine out in the open to correct the problem. I gave up and called the Northern Lights tech guy and he is coming out tomorrow.
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Old 10-10-2022, 09:34 PM   #13
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Did anyone suggest checking the strainer for obstructions?
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