Mowing Kubota diesel overheating.

Flad

Member
Joined
Jul 3, 2016
Messages
39
Location
Victoria
Tractor
cat 428b
I have not to date ever seen a multi cylinder diesel later model engine after 1960 without a thermostat, back then is when diesels first became the engines of choice in every thing from earth moving, trucking, farming and stationary motors Generators and irrigation pumps , mind you I have replaced thermostats where some goose had removed them in places like the Simpson desert to the high snow country, Even big Air cooled diesels have some sort of thermostatically controlled air baffles /vents or fans to maintain constant running temps .

These days most professional diesel service centers use regular oil sampling mostly for engine warranty reasons, Cat do it some times for free for research on their bigger engines, oil sampling will tell if an engine has been running hot or cold or other issues that might become a problem in the future, the oil tells the story. computers can tell lies.
The very first things to be inspected if an engine has been running hot are you guessed it, the thermostat and radiator or cooling system pressure, simplest bits first.
 

Sidey

New member
Joined
Jul 17, 2012
Messages
1
Location
Vic
Tractor
Cas
I’ve got a grasshopper ZT with a Kubota diesel in it. It happens fairly slowly but the temp keeps creeping up. The radiator is clean. The air filter is clean, the fan belt is tight, the fan shroud is in place all but a little bit at the bottom which I don’t think has ever been there. There’s no fan clutch, it’s direct mounted. I’ve taken the thermostat out and ran without it and there’s no change. I put the thermostat in a pot of water and heated it on the stove and the pot was very near boiling before it opened. I honestly thought it would fix the problem taking that out but it didn’t. I might repeat that that test with a thermometer since it was supposed to open at 160 degrees. I’ve taken the side panels and hood off to see if better ventilation would help and it does but not a notable amount. And it blows more heat down my back that way. The radiator is as hot as the block when checked with an infrared thermometer. So it seems to me the radiator is taking heat but not loosing it. I’m pretty much at a loss on this one.
Water Pump possibly not efficient.
 

DutchInNZ

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Joined
Oct 31, 2020
Messages
15
Tractor
Zetor 5745
One of the purposes of the thermostat is to keep the water/engine ect. at the recommended temp. It slows the flow of water through the radiator so that the coolant cools. If it goes thru too fast the coolant will continue to get hotter. You must have a thermostat to slow the water. I ran a dirt track car with a piece of aluminum with a 1/2" hole to slow the flow. It could be your thermostat is sticking too far open.
In line with your comment, when it is cold in your house, you turn the flow in the heating down and when it is warm, you turn it up ?!

If the flow increases, the cooling capacity increases too because of the increased calorific transport. The thermostat serves for one thing only, and that is to decrease the flow when the coolant is too cold and it starts to let more coolant through when the operating temperature is reached. A few degrees over the ideal running temperature and the thermostat opens completely to get maximum cooling. Without a thermostat your engine will likely never reach the right temperature in winter when it is freezing.

A radiator cap has no influence at all on the cooling capacity of a system. It increases the pressure in the system so that the coolant does not boil at the optimum running temperature that is over 98 and up to 105 degrees centigrade, depending on the design of the engine. Only when there is an overheating problem and because of the temperature the pressure gets higher than that, the relief valve opens to protect the system.

That regular high coolant temperature is why one should not try to take the cap off when the engine is hot, because the coolant is over the boiling point 100 Celsius, so hot that at ambient pressure it boils explosively. Just google the pressure/temperature curve of water/steam systems.
 
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Scott Solum

New member
Joined
Oct 24, 2020
Messages
1
Tractor
2020 Kubota zd1211
I am having the same problem, I'm find it to be under powered for the altitude I am at 5200'. The RPM cannot keep the fan spinning fast enough to keep it cool. It actually slows to a very a very slow walk and eventually overheats. A very well built machine with a huge problem.. I am so disappointed the dealer will not help me even though it has less than 20 hours on it.
Good luck, I hope yours is a belt
 

northcreek2624

Gold Member
Joined
Mar 18, 2001
Messages
470
Location
Lake View,N.Y.(WNY)
Tractor
KIOTI DK40(2002)) Jacobsen 628D AWD Turfcat
Since no one mentioned it I will. Your lower radiator hose (suction) may be collapsing. Most have a spring reinforcement to prevent this but, some rely on the hose itself and when they get old they can close off from the suction.
 

Williy

Platinum Member
Joined
Apr 26, 2020
Messages
911
Location
Texas
Tractor
Yanmar YT 235C Yannar YRC 60 rotary cutter, Yanmar RT72 rotary tiller B75 Backhoe & bucket & thumb
Company says: Shell Rotella
  1. Protection against overheating – Excellent heat transfer properties allow heat to transfer more effectively, protect against freeze and boil-over and help keep engines running cool
willy
 

eddieirvine

Silver Member
Joined
May 15, 2008
Messages
129
Location
Indiana
Tractor
Kubota L 3940
Belt slipping could be? hard to tell but i sm guessing change it at you might be good, fan can run pretty slow with worn belt and slipping belt
 
 
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