OK. Thank you all for your advice!
Check the tension on the fan belt, It operates the fan ,water pump, and alternator I believe. It may spin at idle, then slip at higher rpm. The belt may have stretched over the years. But probably the thermostat if you haven't heard any noise from the belt.
The belts seems tight. Although I don't know how to check them when under load.??
Do you see the fluid circulate in the radiator? Does the bottom hose get hot? Radiator cap OK?
No, I can't see the fluid circulate. How would I do that? The bottom hose gets hot, yes.
What are you suggesting I check with the radiator cap?
Is the system full of the proper antifreeze/water mix? Is the upper hose pressurized (hard to squeeze). 10 minutes is way too short of a time for any diesel to overheat. I would remove the thermostat and see if the overheat problem goes away. If that option doesn't appeal to you, you can check the thermostat by placing it in a pot of water. Bring the water to a boil and see if the thermostat opens. The thermostat may have the temperature marked on it (180, 185, etc.) which is the opening temp. Having a thermometer in the pot of water (or IR) would help.
Yes, I've got full coolant. Both top and bottom hoses seem to increase pressure a little when running, but they both feel about the same, and both easily give when squeezed. Is that a problem?
Removing the thermostat seems like it would be hard to do. Won't I have to carefully drain all the coolant? I think I'd need a service manual to make sure I got it right.
Open up rad cap and take flash light and look in at the tops of the tubes is there build up around openings? Rad may need to be cleaned?
I can't see anything from the radiator cap. It looks like I could disassemble the top of the radiator to reveal the tubes, but I'm not sure.
I've seen fins on water pumps completely eaten away, that could be the cause too, no circulation..
I'm totally lost on this suggestion. But if the radiator and hoses are heating up, doesn't that mean that I'm getting circulation?
All good advice above.
Double check your "Radiator fins are clean of debris" . Put a water hose on it and see clean water flow through the fins.
Had that problem on my little tractor. With the battery and the transmission cooler blocking parts of the radiator and dirt build up deep in the radiator it got hot.
Good call. Recheck the simple. The radiator has a removable filter in front of the fins that I had checked and cleaned, but the actual fins were hard to see because the battery blocks access. I removed the battery and found a fine mesh of dirt on much of the fins. I removed the debris and hosed it down.
Most communities have a "Mobile Mechanic" service where they come to you. Their primary customers are truckers but they will do other work.
You have not talked about the age and history of your tractor. A leaking head gasket will let high pressure gases from within the cylinder escape into the cooling system thus mimicking the boiling you think you see.
Invest in an Infrared Temp gun so you are certain you are overheating. A 190 degree thermostat makes everything seem too hot but actually things are as they should be. 130 degrees F will seem very hot to the touch.
Amazon.com: Etekcity Lasergrip 1�8� Non-contact Digital Laser Infrared Thermometer Temperature Gun -58℉~1�22℉ (-5�℃～55�℃), Yellow and Black: Kitchen & Dining
Less than $20.
Never heard of a mobile mechanic around here (rural western Massachusetts). That would be sweet.
My tractor is 10 years old with 540 hours. I probably stress it more than the usual SCUT owner. E.g. I have a 60" brush hog that I regularly use and years ago I remember someone speculating that the large mower was stressful on the SCUT's PTO. And I use a rototiller, too, that works hard. It's definitely possible that there could be cracks. But I don't know how to tell.
If the problem persists after cleaning the rad fins, I'll get a thermometer to check for overheating. If it is overheating, then I'll tackle the thermostat removal/replacement.
Thanks all for many very helpful suggestions. I'll let you know how it turns out.
