My Case 1840 with 1500 hours overheats after about 10 minutes of low speed operation (at least the idiot light comes on). When this happens, the top of the radiator is pretty hot to the touch, but not boiling. The bottom of the radiator and lower hose remains cool; feels like ambient temperature. Water from a garden hose runs through the radiator with no problem. The water pump turns fine and the impeller looks like new. I also suspected the thermostat, but seems to me the upper radiator reservoir wouldn't get hot if the thermostat wasn't opening. There are no bubbles in the radiator reservoir as I have seen happen with a bad head gasket. Any ideas would be greatly appreciated! Thanks, Gordon
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OldMachinist
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Get one those cheap digital meat thermometers (less than $10 at WalMart) and stick in radiator cap opening and see what the temp really is. It may just be a bad sending unit.
Simply feeling the top hose isn't a good indication of thermostat operation. If its stuck closed or mostly closed it will not allow much coolant to leak out to the radiator. They all have a small amount of leakage, so even when its closed it allows a small amount of coolant to move.
You can remove it and drop it in boiling water and see if it opens up. As OM stated, a thermometer is a good idea. Even if you can get hold of an IR one to check the head temperature.
thanks for the replies. The sending unit occurred to me after I posted, as all the indicators don't make much sence when combined. Any idea what the external head temp (or the water temp) should be? The water isn't boiling, and it boils pretty low temp at 7200 feet. I've not been able to find a schematic for this thing; there is a sender near the top radiator hose that was disconnected but putting it back made no difference. Maybe I can remove it and put a real temp guage on this thing. Thanks again! Gordon
You should be running anti-freeze/anit-boil additive anyway, it shouldn't boil.
It should run... 180-190F? i think thats what is stamped on Kubota thermostats from memory.
Adding a true temperature gague into the thermostat housing is a good idea, it tells you how hot it is running, not just to turn a light on.
Thanks again, It normally has antifreeze - gets pretty cold up here in the winter. Just took it out to experiment, and water is really a better coolant for cooling alone. Gonna see if I can find a temp setup that will fit in the hole.......... Trying to see if there is an engine temp as well as coolant temp - some places it uses one name then the other. Spent $180 for a service manual this week. Will help when it gets here. Gordon
