Onan 8 K Generator Coolant?

[Norm4015]

Originally Posted by Bob86ZZ4

Thanks Norm, I'll try that. Prestone universal coolant okay? 50/50 mix.

Prestone will be good. I have used it before.

[bcs430]

Originally Posted by Diplomat Don

hardy1000.....I had the same issue when I changed mine. The generator has an air lock and won't accept the coolant....thus it gets hot and shuts down. You have add the coolant very slowly because the vent tube is at the top of the reservoir.

I panicked on mine and pulled the cover. I removed the radiator hose and filled it that way. You don't have a problem, other than the system isn't accepting the fluid.

I read an article/post once about this issue, but couldn't find it. You might want to check the gen manual.

Like I said....don't panic......you just have to get the air out of the system. It might have even bled down some since you last started it.

Thanks for the info. I have a quiet diesel 10K and just did the flush today. I followed the instructions per the manual and had the same issues. I drained and flushed the radiator. Then I added the coolant (not that slow) and it took just about the entire gallon of the coolant. I fired up the generator and for about 5 minutes it ran great. Then it shut down and I got the overheat code. I let the generator cool down for a few minutes and as I slowly unscrewed the radiator cap, a bunch of air and coolant started spraying out. So, I added more coolant and about a minute after starting, it shut down again.

I did reflush in panic mode, filled up the via hose connected to the pressure cap (once again, took the full gallon) left the cap off, restarted the generator and about a minute later the coolant started coming back up fast and I just shut off the generator.

So...How do you remove the air from the system? Do I just let it sit overnight or do I have to keep starting the generator and let it cycle the air out?

Prior to the flush, the generator worked fine with no overheating issues. I have to guess air is trapped in the system and it has to be bled out.

Any tips/suggestions?

[Barlow46]

Originally Posted by bcs430

Thanks for the info. I have a quiet diesel 10K and just did the flush today. I followed the instructions per the manual and had the same issues. I drained and flushed the radiator. Then I added the coolant (not that slow) and it took just about the entire gallon of the coolant. I fired up the generator and for about 5 minutes it ran great. Then it shut down and I got the overheat code. I let the generator cool down for a few minutes and as I slowly unscrewed the radiator cap, a bunch of air and coolant started spraying out. So, I added more coolant and about a minute after starting, it shut down again.

I did reflush in panic mode, filled up the via hose connected to the pressure cap (once again, took the full gallon) left the cap off, restarted the generator and about a minute later the coolant started coming back up fast and I just shut off the generator.

So...How do you remove the air from the system? Do I just let it sit overnight or do I have to keep starting the generator and let it cycle the air out?

Prior to the flush, the generator worked fine with no overheating issues. I have to guess air is trapped in the system and it has to be bled out.

Any tips/suggestions?

Are you adding the coolant to the plastic tank or are you sliding the rubber fill hose (with the small radiator cap on it) out of the metal bracket and straightening it out and filling it slowly? I have the same 10kw and just recently did mine for the first time. Took my time and had no problem on restart. I did check it frequently after the refill and ended up adding about a pint after it burped a couple of times.

[bcs430]

Yes, I filled per the main rubber hose line with the pressure cap. I did pull the line and lift up as high as it could go and fill the coolant that way.

In terms of pouring slowly, I didnt spill any of the coolant and I didnt use a funnel. Not sure if that's considered nice and slow?

The last time I started it (3rd time), I left the pressure cap off to see if I could relieve some pressure or allow the air to come out, instead of bubbles and burping, the coolant started to come out at a pretty even flow. Obviously the warmer the engine the more forceful, it would come out but I shut it off well before then.

I'll try again tomorrow and see if the coolant settled in overnight.

if you have any other ideas, please let me know.

Thanks.

[Twomed]

Onan coolant change no bubbles.pdf

Here's the Onal manual update on how to avoid air in coolant.

Arrrgh...you got the whole manual, but the update is the supplement at the beginning. Works for 12K and 7.5K also.

[bcs430]

Originally Posted by Twomed

Attachment 6479

Here's the Onal manual update on how to avoid air in coolant.

Arrrgh...you got the whole manual, but the update is the supplement at the beginning. Works for 12K and 7.5K also.

Thanks. I came across that as well late last night. Do I need to disconnect the tubes from the main fill tube and then follow the procedure of blowing the air vent free? do I perform this prior to refilling with the funnel (post flush) or can I do it now without draining the coolant and starting all over again?

Thanks.

[bcs430]

I tried it this am per the instructions and go figure the battery is dead (at least I knew it wasnt holding a charge that well)!

The only issue that I worry about is that the coolant is at the same level as last night. Hopefully the cleared vent will do the trick. I could hear the coolant being cleared out into the reserve tank via the vent tube so fingers crossed it will work after I change out the battery.

[Twomed]

Best to drain (with pressure cap off) and refill. It's overheating because it has an air bubble in the head. That little Kubota is $$$$.

[PEPPER9950]

I had the same problem but it ended up being a broken belt. I could not believe how hard it was to get to the belt and what a small cheap belt Onan uses. I've seen larger and better belts on lawnmowers.

[bcs430]

Drained the coolant out completely. blew out all the coolant in the hoses and refilled using a funnel that went about 3 inches into the fill hose.

Ran the generator with the pressure cap off for about 2 minutes. The coolant did rise and at one point shot out like a geyser for 1 second and then settled back in. Shut it down, put the a new pressure cap on and filled the reserve tank to the "cold" level and viola....it worked!

I also changed the oil and changed out the fuel and air filter. Runs like a champ now... knock on wood....

[bcs430]

Originally Posted by PEPPER9950

I had the same problem but it ended up being a broken belt. I could not believe how hard it was to get to the belt and what a small cheap belt Onan uses. I've seen larger and better belts on lawnmowers.

Where is the belt located? I ran the generator today and the freaking thing shut down again with the same error code...high temperature.

I reflushed again and ran the generator without the pressure cap for a few minutes and sure enough, the coolant came up and started shooting out of the fill tube. Im not sure if that's another air bubble or if it's the belt or thermostat?

[a k]

Check and see if you have a lot of air pushing out the back bottom of generator when its running. If not you threw the belt. There is a belt that drives the Alternator on the generator and water pump and the water pump drives a belt to the fan on the end of the crankshaft. Onan won't sell you a new belt. They have a $330 replacement fan drive but you can get a appliance belt to fit it from a hardware store or supply store. A automotive belt won't fit. It is an A belt or a 4L belt.
You have to pull the top and the Drivers side off to get to the belts. Onan says it's so expensive to adjust the belts , they wait until they shred and then replace them.

[bcs430]

Originally Posted by a k

Check and see if you have a lot of air pushing out the back bottom of generator when its running. If not you threw the belt. There is a belt that drives the Alternator on the generator and water pump and the water pump drives a belt to the fan on the end of the crankshaft. Onan won't sell you a new belt. They have a $330 replacement fan drive but you can get a appliance belt to fit it from a hardware store or supply store. A automotive belt won't fit. It is an A belt or a 4L belt.
You have to pull the top and the Drivers side off to get to the belts. Onan says it's so expensive to adjust the belts , they wait until they shred and then replace them.

There was definitely a lot of air pushing out the bottom front (away from the radiator) so I didnt think it was the belt?

Perhaps im doing something wrong with coolant fill? I flushed it completely, pulled the fill tube out and as high as it could go, inserted funnel with long spout (goes beyond air vent) and poured approximately 3/4 gallon of coolant (peak 50/50 coolant.... requires no water). Then I ran the engine without the pressure cap for a few minutes. The coolant initially went down the fill tube with air bubbles come out of the vent tube here and there and then the coolant started coming back up the fill tube and overflowed all over the place.

What am I doing wrong???

[hardy1000]

Originally Posted by bcs430

There was definitely a lot of air pushing out the bottom front (away from the radiator) so I didnt think it was the belt?

Perhaps im doing something wrong with coolant fill? I flushed it completely, pulled the fill tube out and as high as it could go, inserted funnel with long spout (goes beyond air vent) and poured approximately 3/4 gallon of coolant (peak 50/50 coolant.... requires no water). Then I ran the engine without the pressure cap for a few minutes. The coolant initially went down the fill tube with air bubbles come out of the vent tube here and there and then the coolant started coming back up the fill tube and overflowed all over the place.

What am I doing wrong???

BCS430,

I had the same problem because I filled the radiator first and then the overflow tank which the manual says to do the oppoisite so I had an air bubble also. Make sure the overflow tank is filled up to the line then with the radiator cap off keep starting the generator and checking the tank level. It took me about 5 starts to get the bubbles out and adding coolant to the correct level between starts and then it worked. Hang in there it does get frustrating.