Generator overheating problem

[Mariner]

Ok, it's not actually overheating...or at least it doesn't seem to be. But, I was sitting here on the hook, and I fired up the generator to charge the batteries. It ran for a couple minutes fine, until I noticed suddenly that it stopped spitting water out of the exhaust. I immediately shut it down and began investigating. First I checked the strainer. There was a little slime in it, but it was mostly clear. I cleaned it out, and restarted the generator. Still no water. Temp slowly climbing above 150F. Shut it down again and checked the impeller. It was in good shape. Pulled the hose off the seacock and opened the valve. No water flow. Bingo! Or so I thought. First I tried poking a screwdriver through it, but it didn't work. Eventually I donned the mask and snorkel and braved the (thankfully) 65 degree water with scrub brush in hand. I found the intake screen under the boat covered in sea growth. I scrubbed it off and scrambled back aboard the boat. Fired up the generator and PRESTO! Good strong flow.

But, and here's the problem. As I climbed back down into the engine compartment, I noticed a large amount of water sloshing around in the tray under the generator. It was red and smelled of coolant. I soaked it all up and fired up the generator again. Within a few minutes, again, there it was. I traced it to the coolant overflow (big surprise there).

Here's what I don't understand. If I'm getting good water flow, and the temperature gauge shows that it's still at a safe 150F, why would the coolant be overflowing? Right now I'm letting it cool off before starting it again to see what it does. I'll pull the "radiator" cap off and see if the spring under it is stuck or broken or something, but other than that, I can't imagine why it'd be overflowing.

[Capt Paul]

Mariner,

Just a thought since I do not know your system. The coolant side gets pumped around also correct? May be there is a little blockage in that system that is letting the presure build up?

Paul

[Mariner]

That would have been a posibility, but I just checked the taste of the water coming out of the overflow bottle and it was salty. I can only assume this means that there is a leak in the heat exchanger letting the salt water into the fresh water coolant system. This would also explain why the overflow started out red and slowly turned clear.

Guess we need a new heat exchanger.

[chiefrcd]

Does it have a thermostate like many small engines. I've had similar issues with cars and other small engines and usually it's thermostate related.

[jcollins]

Is there a thermostat? Stuck?

[Mariner]

Unfortunately, the manual doesn't give much in the way of details and crawling around to that side of the genset is very difficult. I'm sure it does have a thermostat. The water doesn't start flowing out of the overflow hose until after it's warmed up (I assume when the thermostat opens). The flow is light but steady. Enough to fill a cup in about a minute, I'd say. The only reason I can think of for getting salt water into the fresh water cooling system is from a leak in the heat exchanger. I assume the leak must have developed when the raw water intake clogged.

[TD]

I had a different problem this last weekend at Neah Bay fishing, but maybe related. I have a Northern Lights on my TE 35 and blew out the heat exchanger intake boot. I took the port side and front panel off the generator to remove the intake boot and remove the core tube heat exchanger out of the manifold. I flushed that out and tried it to find still no seawater flow. I removed the exhaust boot and put a garden hose to the exhaust which flowed great. Then I cleaned out the small [about 3/4""diameter] boot to exhaust casting pipe and found it plugged. Cleaned that out the everything seems to be flowing good. Yes it is very tight working conditions but with the two panels removed it was not bad.

[diversion]

I had coolant leaking out of my header tank cap which I repaired by replacing the cap. They wear out and should be changed whenever you flush the system.

[Mariner]

I finally got around to disassembling and inspecting the heat exchanger. I learned a lot out how it works in the process, but I found nothing wrong. I reassembled it and tried it out. No problems; it works fine now. So, I guess I'll never know exactly what was wrong, but the problem is solved and the generator has fresh coolant. So, I guess it's not all bad.

[Morning Star]

Hello Mariner -

I'm in the process of getting an ALBIN 31 ready for the water, and have the cooling system on my Northern Lights generator torn apart right now.

The previous owner also noted raw water in the engine cooling system (expansion tank), but could not explain the origin. I've also noticed a large amount of salt both on the front of the generator engine, in the area of the water pump, and on the tray under the front of the engine.

My guess is the seal between the inlet and outlet hoses to the heat exchanger, but am still investigating. The raw water/jacket water seal is made by the hose clamps that support the heat exchanger core in the casting, so any dirt, corrosion, or lack of clamping could let raw water into the coolant.

However, I'm still searching, so will let you know if I find anything else.

And yes, the generator is a bitch to work on in an ALBIN 31, especially if the sound covers are still on. I've taken mine off, and mounted the generator assy on a sliding base to improve access. But still is no fun....

Peter Sampson
Morning Star V

[Mariner]

I think I'm reasonably sure what happened, though I can't really be sure. On the day in question, the through-hull strainer became plugged. I went underneath the boat in a dive mask and cleaned it. Water flowed normally after that, but that's when I discovered the seawater coming out of the overflow bottle.

I think when the through-hull clogged, it caused a vacuum (or maybe a pressure build-up) on the heat exchanger. Since the exchanger is secured by rubber boots on both ends, either condition could result in one of the hose clamps slipping, and then raw water would start flowing into the coolant system. It's an odd system and I can't imagine why they designed it the way they did.

[Morning Star]

Thx for the comments. However, I've thought about your reply, and it seems either the heat exchanger core or the seal at the inlet and outlet boots are at fault, since those points are the only interfaces between raw water and engine coolant.

If the intake strainer is plugged, then there would be negative pressure on the intake side of the pump. The lack of water would ultimately cause the impeller to fail, but since the generator outlet is above the waterline, no raw water would be drawn back into the system even if there was negative pressure on the outlet side of the pump too.

Seems to me that the only way to get raw water into the cooling system is either a failed heat exchanger core or a faulty seal between the inlet/outlet boots and the sealing surface on the heat exchanger core. If that were the case, then the raw water pump pressure would force raw water into the cooling system, and it would end up in the overflow tank.

I've got my core out now being cleaned and pressure-tested, so when I get the results I'll let you know.

Also, when I'm next in Seattle (boat show time), I'll quiz the service mgr at Northern Lights and see what his experience has been.

[Mariner]

Peter,

I think you and I are on the same page, we're just describing it differently. What I discovered was that the heat exchanger core was just fine. Again, I can't say for sure whether or not one of the boots had slipped, resulting in a loss of the integrity of the seal, but it seems most likely. Simply disassembling and reassembling the heat exchanger solved the problem. A leak in the seal on either boot is the only thing that could have caused the problem without it persisting after the reassembly.

[Morning Star]

Yes, I agree. Thx for your comments.

As part of the core clean/test I've asked the shop to clean up the sealing surfaces on the core. I'm toying with using some sort of sealant between the boots and the heat exchanger core, say 5200 or Permatex.

You have any thoughts on that idea?

That will be a question I'll ask the Northern Lights svc mgr in Jan.

Thx again.

[TD]

I am certainly not an expert at the Northern Lights Luger but let me offer this info where I had a simular experience. I didn't have any sea water flow out the exhaust.
If the wet exhaust elbow P/N 135616570 plugs up [there is a small port about 3/8" diameter] for all of the sea water to go through, the result is either a blown boot at one or both ends of the exhaust manifold or an overheat. In my case it blew out the intake elbow end cap and allowed water all over. I removed the exhaust end cap, replace with a new one and cleaned out the small hole in the wet elbow which allowed flow again. I may be way off base for your situation, but thought I would share my experience. Good luck.