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Kohler Marine 6.5ESZ Overheating?


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  #1  
Old 06-26-2019, 09:04:26 PM
cstraubs cstraubs is offline
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Default Kohler Marine 6.5ESZ Overheating?

I have a Kohler 6.5esz, Spec 125253. That runs about 15 minutes no load,10 with a load and hard cut shuts down. Won't immediately restart,5 minutes or so it will restart and run about another 10 minutes and shut down.
It has a new raw water pump/impeller,the heat exchanger has been chemically flushed & cleaned. I've had a temp gun all over this thing as it runs & shuts down. Exhaust sensors never got over 100 degrees. Coolant at the heat exhanger is about 150 degrees. Themostat housing,one side stays 180,the other on the cylinder head side never broke 200 degrees. The hottest thing I measured on the entire motor is the top valve cover got to about 230degrees.
I'm totally stumped. The only thing that seems odd is the raw water output is only about 6-8 degrees hotter than the water temp. like its not removing enough heat from the motor? Possible the closed cooling side water pump not moving the coolant good enough???
Thanks guys for your time,
Bobby
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Old 06-26-2019, 09:20:55 PM
Zephyr7 Zephyr7 is offline
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Default Re: Kohler Marine 6.5esz overheating?

Check that the coolant system has been fully primed, no air pockets. Sometimes an air bubble will prevent proper cooling and you might have a hot spot around the temp sensor. The other thing to check is if you have a low coolant level sensor that is triggering the shutdown.

Bill
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Old 06-26-2019, 09:27:52 PM
cstraubs cstraubs is offline
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Default Re: Kohler Marine 6.5esz overheating?

No low coolant sensor....I've bled coolant through the bleeder screw on the thermostat housing and top coolant off at least 10 times over 3 days. Coolant level is never lower than the amount I bled out.
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Old 06-26-2019, 10:57:10 PM
Vanman Vanman is offline
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Default Re: Kohler Marine 6.5esz overheating?

Is it actually the high temperature switch that is shutting it down? Confirmed with a meter?

Keith
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Old 06-26-2019, 11:42:59 PM
cstraubs cstraubs is offline
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Default Re: Kohler Marine 6.5esz overheating?

No,I don't know how to test the switch. I'm just assuming its shutting down by the time it takes to cut off. Its very consistent. Basically 15 minutes no load,and about 10 with a heavy load. Will instantly try to restart and kick off. If I let it sit for 5 minutes,it will run about another 10 minutes. I don't have a service manual. I've heard they are ground side switches?
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Old 06-27-2019, 10:58:04 AM
Zephyr7 Zephyr7 is offline
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Default Re: Kohler Marine 6.5esz Overheating?

That does sound like it may be temperature related. Yes, these are generally ground side (one-wire) switches. You can check them with a continuity light in many cases, the tester would go between battery + and the switch terminal. When the switch changes state, you'd see the light go on or off. If that happens at the same time the unit shuts down, then you know that's the cause.

It's possible the switch is operating at a too-low temperature, but I'd be certain the cooling system is OK before suspecting the switch has drifted. Make sure you have flow and no air pockets. Some engines are a pain to prime.

Bill
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Old 06-27-2019, 02:28:57 PM
cstraubs cstraubs is offline
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Default Re: Kohler Marine 6.5esz Overheating?

This is the same switch that has been in from day one. I have a tempature switch on the way that I am going to plug in once the generator shuts down just to see if it will immediately restart. The generator is shutting down at the exact same time before any of the coolant system was opened,and before I had the heat exchanger cleaned. Which is pretty confusing.
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Old 06-28-2019, 04:31:29 PM
Zephyr7 Zephyr7 is offline
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Default Re: Kohler Marine 6.5ESZ Overheating?

It's possible the switch is failing. They're usually pretty reliable, but anything can break...

Bill
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Old 10-01-2019, 06:00:15 PM
cstraubs cstraubs is offline
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Default Re: Kohler Marine 6.5ESZ Overheating?

Just as an update...it ended up being the controller board. Running good now.
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