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Old 20-12-2012, 05:56   #1
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Genset Overheating !

My genset, a Kohler 9E0Z powered by a Yanmar 3TNE78 overheats after running a few minutes. I have replaced the entire raw water side including the impeller and heat exchanger and the raw water seems to be fine. There's warm water coming out the exhaust and the temperature and amount are pretty much the same as the exhaust from the main engine. When I stick my finger in the coolant tank I can feel the coolant circulating but it seems really hot really quickly. I have removed the thermostat to make sure it isnt blocking the flow through the heat exchanger. The coolant temp will go from room temp to 150 after about 10 minutes running time and then up past 180 in a few more minutes. It will continue to creep up past 210 at which time I shut the thing off. I started trying to remedy this by flushing the coolant side of the system and the old coolant was rusty looking and had some gel like material gooing things up. It seems to circulate well now but possibly has some partial blockage inside somewhere. I have done everything I can think of with no success Any suggestions as to how to locate the blockage and clear things up will be greatly appreciated, or if you think there may be another cause please let me know. Thanks in advance.
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Old 20-12-2012, 06:01   #2
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Re: Genset Overheating !

I would try Barnacle Buster thru both the raw and fresh water sides.
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Old 20-12-2012, 07:33   #3
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Re: Genset Overheating !

It sounds like you have cleared everything in the raw water side. I have experienced loose rubber impeller parts that have reduced flow in the raw water circuit. They collected at the heat exchanger on my Onan. If you have any history of worn impellers, and have reduced flow you need to get them out of the system.

You've changed the heat exchanger. Otherwise, you might consider running a rod through the tubes to clear any blockages.

Maybe flushing the coolant side several times will improve it.
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Old 20-12-2012, 10:25   #4
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Re: Genset Overheating !

Pull and check the discharge elbow for mineral buildup. That can reduce raw water flow also. If that's not it then maybe pull the fresh water pump and check the impeller. I have heard of impeller vanes corroding away.

I'm betting its the discharge ell getting a bit of blockage...
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Old 20-12-2012, 10:42   #5
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Re: Genset Overheating !

What is the cause of the gel in the coolant side of the system? That certainly has to be taken care of by reverse flushing until clean and then the system filled with the proper coolant.

As Sailorchic says if you haven't checked and cleaned the water injection elbow that could very well be the cause.
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Old 20-12-2012, 11:22   #6
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Re: Genset Overheating !

If the engine is not distressed at 210, it could be the gauge or sender. A short run to 230, to see if if opens the heat exchanger cap, shouldn't hurt the engine, and will verify whether or not its the gauge.
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Old 20-12-2012, 15:58   #7
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Re: Genset Overheating !

If the thermostat is failing, it might not be opening the allowing flow appropriately...

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Old 21-12-2012, 08:07   #8
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Re: Genset Overheating !

Thermostat? If the coolant was gelled, then the thermostat could easily be skanked up.

Is the fan belt tensioned properly? If it's slipping the coolant pump won't be running properly.

New water pump? I'm talking about the coolant circulating pump, not the raw water pump.

An IT thermometer could tell you a lot. Shoot different parts of the coolant loop to see what the temp is. If you have circulation problems resulting from blockages or pump issues, it should show up a differences in coolant temperatures.

You said you flushed the gel out of the cooling system and refilled. Could it be air locked? That would prevent the coolant from circulating and cause over heating. If you grab the coolant hoses and pump them with your hand like you would squeeze and stress ball or a primer ball on an outboard, it very effectively purges the air. You can usually hear when the coolant is flowing smoothly rather than girgling and burping.

I'd guess an air lock is the most probable.
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Old 21-12-2012, 08:19   #9
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Re: Genset Overheating !

Quote:
Originally Posted by YACHT TARENTELA View Post
My genset, a Kohler 9E0Z powered by a Yanmar 3TNE78 overheats after running a few minutes. I have replaced the entire raw water side including the impeller and heat exchanger and the raw water seems to be fine. There's warm water coming out the exhaust and the temperature and amount are pretty much the same as the exhaust from the main engine. When I stick my finger in the coolant tank I can feel the coolant circulating but it seems really hot really quickly. I have removed the thermostat to make sure it isnt blocking the flow through the heat exchanger. The coolant temp will go from room temp to 150 after about 10 minutes running time and then up past 180 in a few more minutes. It will continue to creep up past 210 at which time I shut the thing off. I started trying to remedy this by flushing the coolant side of the system and the old coolant was rusty looking and had some gel like material gooing things up. It seems to circulate well now but possibly has some partial blockage inside somewhere. I have done everything I can think of with no success Any suggestions as to how to locate the blockage and clear things up will be greatly appreciated, or if you think there may be another cause please let me know. Thanks in advance.
Hi, I think something could be wrong with the main gasket.
If so there is a serious leak wich explains water in the exhaustsystem.
Just an idea, coming from my experiance with volvo penta enginges.

Good luck!
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Old 21-12-2012, 08:20   #10
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Re: Genset Overheating !

My vote is for an airlock too. Some little gennies have very specific bleeding procedures to ensure that they aren't airlocked. And if there is an airlock then it won't be circulating. Just be thankful that it is heating up the sender because sometimes when they airlock the get hot without the sender ever knowing about it.

I'd post over on SmokStak. There's lots of really good generator techies over there. Or at least search their archives.
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Old 21-12-2012, 09:29   #11
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Re: Genset Overheating !

Welcome to the club!

Kohlers are notorious for this problem. I have more or less the same generator (a 230 volt 6.5EFOZ) and have had exactly the same problems.

Before you do anything, you should pull the heat exchanger and remove bits of impeller from it. You should also pull the exhaust elbow and make sure it's not blocked.

Then you need to deal with what is almost certainly an airlock. You have to burp and burp and burp the hoses, keep patiently refilling, until you get the air out. What I do after this is start it, and put an infrared thermometer on the flange above the fresh water pump. This is where heat will go up fast if coolant is not circulating. Feel the hoses to the heat exchanger. If those hoses get hot and the flange stays cool, you're in business. If not, however, then shut the gennie down before it shuts itself off, let it cool a bit, then start burping hoses again. It is tedious but it eventually works.

If you've got goo in the fresh water side (I had this too) then you've either got a bad heat exchanger letting salt water into the fresh water side, or somewhere down the road someone put pink antifreeze in after having had green antifreeze. Are you losing coolant?

If you are not losing coolant, then I would flush about 20 times (and every time you do it, you have to repeat the burping/infrared thermometer ritual). Then put in new pink antifreeze and forget about it.

If you are losing coolant, then this adds up, I think, to a leaky heat exchanger, which can easily happen if you fail to replace the pencil anode in time. This is what happened to me, and I'm about to replace the heat exchanger, which is not cheap.
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