woodylmiller Posted June 28, 2023 Share Posted June 28, 2023 10K gen. Shut down the other day. Not completely sure it was a hi temp shut off. But there was some coolant leak when I restarted. Didn't seem like an overheating issue on the gen. Got home and started looking for leaks. The leaks turned out to be the cap on the overflow tank and also the drain tube from the tank. The cap's O ring was shot, so I replaced that. I replaced the radiator cap and went from 13 lbs to a 16 lbs cap. Pulled the fill tube out and held up high to fill with coolant. Ran gen and watched after a few minutes the level of coolant in the overflow begin to rise and then overflow throught the tube but no longer from the cap. When the gen cools ALL coolant is sucked back into the engine. Today I decided to not refill the coolant from the last overflow, maybe there was just too much coolant? Doesn't seem possible, but who knows. Ran the gen with the overflow tank empty. Same thing, after running the coolant began to fill and over flow the tank again. My next guess is the thermostat is not opening. With the engine hot and the overflow tank full of hot coolant I felt for heat on the radiator surface and it was cool compared to the rest of the gen. Having some issues finding a good coolant flow chart to see which hoses to what. On the thermostat housing is a larger hose, 1 1/4 - 1 1/2" hose, which I believe is the return from the radiator or most likely the supply for the radiator since it would be a gravity flow in that direction. Not sure. I had Cummin's do the the 1000 hour coolant system service, that was around 400 hours ago. Have no issues with the gen except for the lift pump and a bad connector. Where to buy reasonably priced parts? Cummins/Onan is a ripoff. Looks like they want $75 for a thermostat. Bullcrap! Anyone ever have this problem? I know that during a fill you have to lift the lift tube/radiator cap as high as possible, and I did that. I seems to me there has to be a flow restriction somewhere. Not a loss of system pressure from the cap, causing high water temps so maybe the thermo is not opening? One other thing. I do not have a actual heat gauge for the gen. Looks like just a high temp cut out sending unit on the thermo housing. Anyone ever add a gauge to their gen? Thanks, Woody Miller 09 Dynasty Link to comment Share on other sites More sharing options...
Ivan K Posted June 28, 2023 Share Posted June 28, 2023 For non generator specific engine parts I would look at the engine manufacturers parts house. Kubota? If so, used in small tractors etc. Mine is a pickup engine used in small Isuzu trucks. Link to comment Share on other sites More sharing options...
96 EVO Posted June 28, 2023 Share Posted June 28, 2023 Stuck thermostat certainly sounds possible! Overflow tank level on mine barely moves! 1 Link to comment Share on other sites More sharing options...
woodylmiller Posted June 30, 2023 Author Share Posted June 30, 2023 Tested thermostat and it opens and closes. Removed water pump, looks fine to me. Put things back together and filled with water through the thermostat housing. Ran and I got some overflow from the tank, but very little compared to before. But now I can feel the hot water going through the supply and return hoses to the pump and there is heat on the radiator. So a complete drain now and refill with coolant and hope. My guess at this point was a serious air lock preventing proper amount of coolant in the system. Strange, but what else is new? Every bone in my body aches from all the crawling into and out of that little cubby to work on the generator. Hopefully just a few more in and outs and I'm done with that. Woody Miller 09 Dynasty Link to comment Share on other sites More sharing options...
96 EVO Posted June 30, 2023 Share Posted June 30, 2023 14 minutes ago, woodylmiller said: Tested thermostat and it opens and closes. Removed water pump, looks fine to me. Put things back together and filled with water through the thermostat housing. Ran and I got some overflow from the tank, but very little compared to before. But now I can feel the hot water going through the supply and return hoses to the pump and there is heat on the radiator. So a complete drain now and refill with coolant and hope. My guess at this point was a serious air lock preventing proper amount of coolant in the system. Strange, but what else is new? Every bone in my body aches from all the crawling into and out of that little cubby to work on the generator. Hopefully just a few more in and outs and I'm done with that. Woody Miller 09 Dynasty Plenty of air blowing thru your rad? As in, belt still tight? Link to comment Share on other sites More sharing options...
woodylmiller Posted July 3, 2023 Author Share Posted July 3, 2023 Everything seems to be working again. Go figure. No idea what was going on. Radiator is now hot, supply and return hose hot and under pressure. Maybe just the fact of taking everything apart including removing the water pump was what was missing. Installed a temp gauge to the system so I can monitor the gen from now on while it's running. Strange that there is no gen status lights/gauges to provide current conditions. The gen had stopped running at some point, I didn't notice the light on the switch was off, so I had no idea; overheat, fuel problem or did it just decided to quit. A water temp gauge will help me keep track of what the gen is doing. Woody Miller 09 Dynasty Link to comment Share on other sites More sharing options...
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