Generator over heat on restart.

steve.barnett71 · July 09, 2016, 10:15:50 AM

We are at Kentucky speedway this weekend. We ran our Onan Diesel generator overnight, turned it off this morning for just a few minutes then decided to turn it back on. It almost immediately overheated and pushed coolant out into the overflow tank. Any ideas what that could be??

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thomasinnv · July 09, 2016, 12:22:08 PM

Stuck thermostat or failed water pump?

luvrbus · July 09, 2016, 12:27:41 PM

Quote from: thomasinnv on July 09, 2016, 12:22:08 PM
Stuck thermostat or failed water pump? or air bubble

Utahclaimjumper · July 09, 2016, 01:07:35 PM

Most Onan diesels have a belt driven water pump,, these belt do break occasionally.>>>Dan

brmax · July 09, 2016, 06:01:32 PM

Does this have an overflow tank for the coolant/antifreeze, as this level is pulled back in the motor upon shut down, and cooling off as there is a vacuum produced.
If this tanks is a bit low for "some reason" it may pull air when doing its normal cool down. So there may be a stubborn air pocket introduced that's about impossible to remove without filing up the coolant system by way of a vacuum method tool.
I'm not real familiar with the powerplant, and curious is the motor a Cummins.
good luck and keep us posted.

Floyd

chessie4905 · July 09, 2016, 07:31:34 PM

How hot was it out?Why did you shut it off for a little bit? Had it been running under a considerable load when it was turned off? Maybe the heat soak didn't have a chance to dissipate. Make sure the pressure cap is working and of the proper psi rating. How clean is the radiator? Any paper or some other obstruction get up against it causing blockage?

steve.barnett71 · July 10, 2016, 06:36:37 AM

Quote from: chessie4905 on July 09, 2016, 07:31:34 PM
How hot was it out?Why did you shut it off for a little bit? Had it been running under a considerable load when it was turned off? Maybe the heat soak didn't have a chance to dissipate. Make sure the pressure cap is working and of the proper psi rating. How clean is the radiator? Any paper or some other obstruction get up against it causing blockage?

Not sure how hot it was, Onan controller just flashed code that it was in an overheat condition. It is an Isuzu engine. It had ran over night with all ACs on and hot water heater. I shut it off just to save fuel because we were gonna be gone a few hours. I then realized that I need to retract the power awning since it was windy and the previous owner wired it to only function off of shore power or generator. It has a new pressure cap and radiator is perfectly clean. I ran it without the cap yesterday to help purge air, added fluid and restarted. It has now been running for about 18 hours

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Oonrahnjay · July 10, 2016, 06:06:34 PM

Quote from: steve.barnett71 on July 10, 2016, 06:36:37 AM
Not sure how hot it was, Onan controller just flashed code that it was in an overheat condition. It is an Isuzu engine. It had ran over night with all ACs on and hot water heater. I shut it off just to save fuel because we were gonna be gone a few hours. I then realized that I need to retract the power awning since it was windy and the previous owner wired it to only function off of shore power or generator. It has a new pressure cap and radiator is perfectly clean. I ran it without the cap yesterday to help purge air, added fluid and restarted. It has now been running for about 18 hours

Pretty much perfect conditions for making an air bubble and then purging it. Seems to me the 18 hours running thing is a good sign.