I have a Kubota KX161-3 which overheats in a relatively short time when in use. I have replaced the coolant and installed a new thermostat and 2 x new temperature sensors. The temperature is showing on the instrument gauge but it is only approx 1/8 of full scale ie. not really showing as hot. It is only after I turn off the engine that I gear the overflow bottle tube bubbling away. Can anyone offer an explanation of: - why is it boiling so quickly but not showing on the gauge. - how can I diagnose/fix it
Assuming the engine is running fine, correct timing, not overloaded. Check the flow, by checking the temp of the radiator inlet and outlet. If you can see anything with the cap off you can check that, hopefully it's holding it's water and not bubbling. Could be a plugged radiator (anybody kept adding hard water?) or a broken water pump impeller? Also how long have you had the machine? how long has it overheated? before you changed coolant? what drained out of the coolant?
Does the radiator cap still have a working valve (ie only letting coolant through at a certain pressure and not all the time)?
could be a blowen head gasket presurizing the cooling system
purchase a raytek laser thermomter. best $50 you can spend if you own equipment. verify the guage is accurate with the laser thermometer. take a water hose or air compressor and clean the radiator out. remove the radiator and have a radiator shop soak and clean the radiator on the INSIDE. they get dirty on the inside too, and the ends of the internal tubes can plug with deposits. flush the engine while the radiator is pulled. if the above doesnt fix it, spend $15 bucks on an oil sample kit, to check for antifreeze in your engine oil.
Chris, your determining that the engine is overheating because you hear bubbling in the overflow bottle? That's basically normal operation.The coolant circulation stops,the fan stops pulling air through the radiator,some localized heating takes place which raises the system pressure and the rad. cap allows the excess pressure to vent to the overflow container.Afterwards in the middle of the deep dark night when all is cooled.The coolant system pressure drops below atmospheric & sucks the previously expelled coolant back in.Magic! Of course, if your radiator cap is not sealing,preventing the coolant system from maintaining the designed pressure,that would make the overflow container to ... overflow. Regularly. And if you have not bled out all the air after some service work,then the air would hopefully collect at the system high point (the cap) and be purged when the system burps (bubbles).Or, not allow the temp sensor to be completely 'wet' giving an incorrect reading. Is there an air bleed screw somewhere near the thermostat housing (or elsewhere)? Otherwise,if you always have bubbles you prolly have a head gasket leak,pumping gasses into the coolant system. Bummer. Also, you really need to find out what the actual temperatures are going into and out of the rad. HTH Jay
HAH! Me and my big mouth! Yesterday I'm puttering around the yard with some little clean up projects and I find fluid all over my tracks.Inline with where I was skewing. Looks like a coolant line from the rad. to the chassis mounted drain fitting. Lucky me. J