Hey everyone! Long-time lurker, first time poster. I purchased a 1999 Cat 939C Hystat 3 years ago. Since purchase, it has consistently run hot and seems to hover about 1/4 of the way into the yellow (not quite to the solid yellow portion but well into the striped yellow portion of the temp gauge). The machine has been regularly serviced, including having the radiator flushed, coolant replaced, and all filters replaced. The fins are in pretty decent shape on the radiator and it feels like sufficient airflow is making it through the oil cooler and radiator. I did replace the thermostat which made the problem worse, only to realize that the previous thermostat had been cut wide open. I put the old thermostat back in once I realized what had been done. I also pressure wash the radiator from time to time to try to prevent excess dust buildup. Thoughts on what else could be causing the temp issues? The machine is tight otherwise and perfect for the farm where I have it. Thanks in advance!
Welcome to the Forums owent! Glad to have you. Unfortunately I am no mechanic but we have many knowledgable wrenches here on HEF willing to help. How is the water pump? Is it pushing the water it should? Good luck!
Is your perception of overheating only based on what the coolant temperature gauge reads.? Is there any possibility that the gauge is incorrect.? If the answer is yes then the first thing I would suggest is to confirm the data with an infra-red temp gun. Take the temp at the thermostat housing and the bottom radiator hose where it returns back to the engine. Post your findings.
Did you install a genuine Cat temperature regulator.? If so what Part Number.?
Thanks Nige! Very much appreciate the response. I should add that the machine does run really well until the temperature reaches elevated levels (typically within an hour but sometimes a little bit longer depending on working conditions and what I am doing - generally knocking over trees and pushing to the pile). I've done the temp test before but can't remember the exact results. Will do again and post results. I've tested with an infrared thermometer and confirmed temp is in the 230+ range and that the gauge is accurate. I have experienced some boil-over before at higher temps. I don't have the part number, but it was a genuine cat part from Thompson Cat in Nashville. However, after operating and the temperature issue being worse, we put the old thermostat back in that was cut open. Water pump was replaced around 500 hours ago and belts are tightened to spec.
It would be good to have some numbers. The fact that the machine only works with a temperature regulator with the guts cut out of it suggests there is a major issue somewhere. Does the fan on your machine blow the hot air out of the engine compartment or suck cool air in from outside.? Both options are available for a 939C. BTW A S/N would help to dientify how it was built. You list a lot of things that have been done to the cooling system but nothing regarding the radiator. Has it been removed and cleaned internally.? Also can you post some good photos showing the external condition of the radiator core.