Coolant flush - 11.5 kW genset

[ADKgenset]

Time for me to flush the coolant in my Onan DNAD 11.5 kW genset. Powers an off grid cabin. Have never done it, and guessing that’s why the generator is shutting down on occasion when temps are just in teens. Plugging in block heater solves issue, so really hope it’s just a matter of coolant that’s waaaaay too old.

Questions about the flush procedure :
-all I know is draining at petcock. How do I ensure getting all the old stuff out?
-Flush with distilled water, run for a few minutes?
-in terms of eliminating bubbles, is it sufficient to just fill slowly?
-necessary to change the cap after?

I am planning to use a hydrometer to test the old stuff, just out of curiosity.

Any advice appreciated, clueless rookie here.

 

[grsthegreat]

boy, unfamiliar with that exact model, but i know on a few generacs ive serviced over the years, you have to bring engine up to warm enough temps to open the thermostat to allow the trapped fluids to flush. Where it gets tricky is sometimes the thermostat closes and doesnt allow new fluids into engine.

Im sure even if the fluids in radiator are the only fluids flushed while the original Remains within the engine, it wouldnt be the end of the world. At least most of it would be new.

On old cars, we used to flush the radiators and engines by replacing radiator fluids, than running engine to open tstat and then replacing fluids again.

 

[mrmikey]

If easy I'd remove the thermostat, drain and fill with distilled water and vinegar, run 'till warm, drain and fill with distilled water, drain, install a new thermostat and refill with a 50/50 mix.

 

[LouNY]

I'm confused;

Time for me to flush the coolant in my Onan DNAD 11.5 kW genset. Powers an off grid cabin. Have never done it, and guessing that’s why the generator is shutting down on occasion when temps are just in teens. Plugging in block heater solves issue, so really hope it’s just a matter of coolant that’s waaaaay too old.

Questions about the flush procedure :
-all I know is draining at petcock. How do I ensure getting all the old stuff out?
-Flush with distilled water, run for a few minutes?
-in terms of eliminating bubbles, is it sufficient to just fill slowly?
-necessary to change the cap after?

I am planning to use a hydrometer to test the old stuff, just out of curiosity.

Any advice appreciated, clueless rookie here.

The generator is shutting down while running?

The ambient temps are in the teens......Celsius or Fahrenheit?

Plugging in a block heater helps the issue, so more heat helps.

Is the engine running so cold that it's stuffing the flame out in a running engine?
I've only seen that happen in light loaded engines in extreme sub zero temps.

 

[RjCorazza]

I suspect the shutting down is not related to the coolant, but sounds like coolant is long overdue.
I quit using the radiator petcocks after breaking a flimsy plastic one. I drain from the lower radiator hose, fill with distilled water, run up to operating temp... repeat until clear, but I've never had to flush more than twice.

 

[ADKgenset]

I'm confused;

The generator is shutting down while running?

The ambient temps are in the teens......Celsius or Fahrenheit?

Plugging in a block heater helps the issue, so more heat helps.

Is the engine running so cold that it's stuffing the flame out in a running engine?
I've only seen that happen in light loaded engines in extreme sub zero temps.

It will shut down while running when temps get into teens (Fahrenheit). Fuel is either 50/50 or straight kerosene at those times, so it shouldn’t be gelling.

5w30 or 10w30 oil, per manual at those ambient temps.

Checked fuel for water, none detected on dipstick with water detecting paste.

Fresh fuel filters prior to shutdowns.

Given that it’s never had a problem above freezing, concluding the cold has something to do with it. Figure coolant change can’t hurt.

 

[ADKgenset]

If easy I'd remove the thermostat, drain and fill with distilled water and vinegar, run 'till warm, drain and fill with distilled water, drain, install a new thermostat and refill with a 50/50 mix.

Thanks. I can’t find thermostat location in manual, and haven’t done this before. Forgive my ignorance, but what/where should I be looking?

 

[Ken]

Thanks. I can’t find thermostat location in manual, and haven’t done this before. Forgive my ignorance, but what/where should I be looking?

This is a 4 cyl. 4 stroke 60cycle 1 ph.120 volt 1800 RPM Kubota engine
Used on Marine applications to be shutting down on tempurature of low teens.
look for other reasons.
maybe a sensor or loose connections.
Key to start. normal
quick temperature rise running
under this type application most likely not overloaded engine
record keeping of filters and past Maintenace.
Have you added fluid to radiator or looked for leaks
My past experience engine would be kept with heater to ensure easy starting.
We used for Micro wave towers the Kubota ran 24/7 only shut down for oil change and filters.
Order repair book from Onan How many hours on engine?
You have a good set up for this type of need.
ken

 

[5030]

boy, unfamiliar with that exact model, but i know on a few generacs ive serviced over the years, you have to bring engine up to warm enough temps to open the thermostat to allow the trapped fluids to flush. Where it gets tricky is sometimes the thermostat closes and doesnt allow new fluids into engine.

Im sure even if the fluids in radiator are the only fluids flushed while the original Remains within the engine, it wouldnt be the end of the world. At least most of it would be new.

On old cars, we used to flush the radiators and engines by replacing radiator fluids, than running engine to open tstat and then replacing fluids again.

Perfect answer. My Generac JD Diesel powered standby requires a coolant flush and recharge every 3 years and is exactly how I do it but this last time I switched from conventional Glycol to the Global orange long life coolant. Having said that I'll still adhere to the Generac recommended change intervals. Mine is turbocharged as well.

If I was the OP, I would also replace the rad cap and install a new thermostat. Heat and cool cycles degrade the additives in conventional coolant no matter what. Some, but not all thermostats will have a bleed hole in the body to allow complete draining without vapor lock.

Not sure if my JD Turbo diesel engine is dry linered or wet but regardless it will get changed on the recommended interval.

Not sure what a hydrometer would tell you. If the coolant has never been changed, chances are it's acidic anyway and has long lost it's additive package. I'd be more concerned with the internal condition of the radiator than anything else. Old shot coolant tends to clog up the passages. Easy to determine by looking in the top with the rad cap removed and observing the top of the passages. You can buy rad flush at any auto parts emporium. Just follow the directions on the package.