What's your Onan Generator coolant level?

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I ask this question to make you go look! At the balloon fiesta this past October quite a few of us including ME were low on coolant. It's one I overlooked and I didn't have the "stuff" to put in to top it off. Thankfully Cummins had a booth and they were topping off coolant as a courtesy. Don't forget to check your GEN coolant level. You can check it in the white plastic on the front (at least on mine) to make sure it's between the cold and hot marks.
 
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Good tip, @Neal. As soon as the current monsoon lets up, I'll go out and check mine.

TJ
 
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I need a new shed to store coolant...

purple fully formulated for the coach
yellow century heat transfer for the Oasis
Red OAT for the Jeep
Pink NOAT for the Toyotas
and what’s this stuff...looks like another fully formulated like the purple but uses DCA4 instead of DCA2 supplemental coolant additive. Molybdenum? Yeah, gotta have some Molybdenum in your coolant. Geesh.... I’m getting a coolant headache.

Just dropped off three gallons of green Preston at the recycling center...nothing I own uses good old green stuff anymore.
 
Last edited:

Jim

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I need a new shed to store coolant...

Just dropped off three gallons of green Preston at the recycling center...nothing I own uses good old green stuff anymore.
I know, right? What happened along the way? :)
 
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Side note, keep spare O ring for the fill caps, on the other coach at two years both the oil and coolant rings cracked (dry rot) when I was checking them.
 
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Depending on your main engine, this stuff mentioned above could also be used in it, so you can get buy carrying one. NOTE: if using the 360HP Cummings engine, the coolant for that one is DIFFERENT than for the other bigger engines. Freightliner in Phoenix area had the correct one for 12 dollars a gallon. Once I got the air bubble out of the engine, I have not had to add any coolant at all. The genset on the other hand I check about every two weeks depending on use.
 
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Do you remember what color it is? Mine is green. I just ordered a gallon so I hope its green. RV Services said stick with the same color.

I don't remember the color but I thought yours was blue when we checked it. I only remember half the things half the time so who knows... 😷
 
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Some things to remember.
Change Radiator cap on ONAN Genset every two years. Ok, this is one of those things I do about every 3 years, when I change the one on the MH Main Engine too.
Change Coolant every two years or 1000 hours whichever is closer. Actually I do mine between 3-5 years, depending on hours and where I have used it.
Oil and Filter every Year, or 100 hours.
Fuel Filter - I do mine every other year on it's anniversary of purchase. Messy Job. So I try to combine it with my annual genset service, this year Freightliner did it, so not going to worry about it till Aug. 2021 if we still got coach. I used to have a Fleet guard Coolant Chart showing which one, blah, blah, blah. Cannot fine it now. Looked into owners manual could not find specification either, will keep looking. The one for the engine in the Ventana is different than the stuff used in the genset I think. Again, brain cells are full, don't remember.
Note: Onan recommends exercise of the genset every month for 2 hours at half load. That would be charging batteries, and one a/c unit running. Doing the heat pump would also qualify as well. This keeps clean fuel in it, keeps the contacts working and generally machinery is supposed to run.
 
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Some things to remember.
Change Radiator cap on ONAN Genset every two years. Ok, this is one of those things I do about every 3 years, when I change the one on the MH Main Engine too.

----- interesting. All of my vehicles over the last 45 years never needed an oil radiator replacement. All ran to 70,000 -167,000 miles
 
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Thanks Neal-I dutifully checked and found it low. Question, do you fill to the "Min-Cool" mark, "Max-Hot" mark, or somewhere betwixt?
 
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I would fill it halfway between the hi/lo marks
 
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I would fill it halfway between the hi/lo marks
Dumb question but I need to know do I fill it pouring it in thee opaque white plastic container or inside the Gen itself?
 
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Clearly indicated on the CAP of the coolant tank is the word COOLANT. Take the cap (cannot remember color of cap) off - twist - not threaded, and fill that tank to within 1" or so of full. This is the overflow tank. Regardless, you should check the level, at least once month, (manual says daily but if not used and not leaking!!!) and if you run genset the required 2 hours as prescribed then after it has cooled down, like the next day works. The coolant should be blue I think, but the same that goes in the engine (diesel assumed) will work, if gas powered, and genset is not, then consult owners manual for correct type. I have attached the operators manual for the 7.5-8.0 KW diesel powered units. Take note of the coolant section. And please also note, the radiator cap should be replaced every three years, when you drain out the old coolant and replace with new. I believe the main engine also needs this done, cannot remember the interval.
 

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Clearly indicated on the CAP of the coolant tank is the word COOLANT. Take the cap (cannot remember color of cap) off - twist - not threaded, and fill that tank to within 1" or so of full. This is the overflow tank. Regardless, you should check the level, at least once month, (manual says daily but if not used and not leaking!!!) and if you run genset the required 2 hours as prescribed then after it has cooled down, like the next day works. The coolant should be blue I think, but the same that goes in the engine (diesel assumed) will work, if gas powered, and genset is not, then consult owners manual for correct type. I have attached the operators manual for the 7.5-8.0 KW diesel powered units. Take note of the coolant section. And please also note, the radiator cap should be replaced every three years, when you drain out the old coolant and replace with new. I believe the main engine also needs this done, cannot remember the interval.
Thank you. At the top of the tank there are two cap marked (coolant and oil). The coolant one I took off and didn't know if I put it in there or in the radiator itself. There is a min fill mark and a max fill mark in the lower right side of tank. Fluid is not visible. should I go to 1 inch of max or 1 inch of top of tank? Also do I mix 50/50 distilled water and coolant? The radiator cap is inside the Gen right?
 
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Use 50/50 pre-diluted ethylene glycol (most common) and pour it in the tank. Mine had the whitish colored cap labeled coolant. Somewhere between the min/max cold level markings on the tank is fine.
 
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Use 50/50 pre-diluted ethylene glycol (most common) and pour it in the tank. Mine had the whitish colored cap labeled coolant. Somewhere between the min/max cold level markings on the tank is fine.
Thank you so much. First time doing outside work on rig. I'm female and 67 but still like to save a dime when possible!
 
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Thank you so much. First time doing outside work on rig. I'm female and 67 but still like to save a dime when possible
What model generator do you have? Onan require special coolant in many cases
 
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