Mowing Kubota diesel overheating.

   / Kubota diesel overheating.
  • Thread Starter
#91  
If the thermostat is out, the radiator is not clogged, and the fan has its blades and spins when running (loose belts), it points to a water pump that the impeller may be slipping or have a shear pin that has been sheared or more likely the belt is broken/missing or too loose.
If the system is at least reasonably clean, the fan turns, and the thermostat is out, it is almost surely the water pump impeller or belt preventing the coolant from circulating.

Dane…

The water pump is good. In this picture it’s got a water hose hooked up but it emptied the radiator at the same or faster rate on its own.
IMG_0217.JPG
 
   / Kubota diesel overheating.
  • Thread Starter
#92  
Exactly what model is this Kubota zero turn diesel mower you have ?
i have a Kubota ZD21 with a little over 1,200 hours, in hot weather the temperature gauge has alway ran close to the red zone but so far it has never overheated at least not that I’m aware of, I have always removed the covers-screens when done mowing to blow off any debris with a leaf blower. Changed the antifreeze about 5 years ago and I will only use premixed antifreeze in everything I own, guess it’s about time to change the antifreeze again.
But after reading this thread I am definitely considering applying Some kind cleaner to the outside of the radiator when it’s cold and let it soak awhile before washing it off with a garden garden hose, I have done that with some other radiators and always been surprised at the amount of stuff that comes out.

It’s a grasshopper 428d with a Kubota diesel.
 
   / Kubota diesel overheating. #93  
besides what you have done already, make sure the belt isnt slipping, check for a combustion leak into the cooling system, also pull the water pump and verify the impeller is in good condition. take the radiator to a shop , have them pull one tank and rod the tubes. even though it seems like it has good flow there maybe enough tubes clogged to cause the overheat.
 
   / Kubota diesel overheating. #94  
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.
Have you considered a leak either in the head gasket, the seals between a cylindar and the block. Try using a sealer. You might have a leak so small it's undetectable in the exhaust. You've also indicated it seems to gert hotter with time, indicating engine expansion is expanding the leak. https://www.google.com/search?q=eng...ome.1.0l10.20939j0j7&sourceid=chrome&ie=UTF-8
 
   / Kubota diesel overheating.
  • Thread Starter
#95  
Exactly what model is this Kubota zero turn diesel mower you have ?
i have a Kubota ZD21 with a little over 1,200 hours, in hot weather the temperature gauge has alway ran close to the red zone but so far it has never overheated at least not that I’m aware of, I have always removed the covers-screens when done mowing to blow off any debris with a leaf blower. Changed the antifreeze about 5 years ago and I will only use premixed antifreeze in everything I own, guess it’s about time to change the antifreeze again.
But after reading this thread I am definitely considering applying Some kind cleaner to the outside of the radiator when it’s cold and let it soak awhile before washing it off with a garden garden hose, I have done that with some other radiators and always been surprised at the amount of stuff that comes out.

It’s a grasshopper 428d with a Kubota diesel.
 
   / Kubota diesel overheating.
  • Thread Starter
#96  
   / Kubota diesel overheating. #97  
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.
I know you have probably checked this but I'll mention it anyway..
I had a similar overheating problem. Went to dealer and described it. He said "you been mowing grass?". I had been. He said, "Did you clean the grass off the removeable screen in the engine compartment?"
He was right. I cleaned it, the problem went away and I learned something.
Thought it might be worth mentioning.
 
   / Kubota diesel overheating.
  • Thread Starter
#98  
I know you have probably checked this but I'll mention it anyway..
I had a similar overheating problem. Went to dealer and described it. He said "you been mowing grass?". I had been. He said, "Did you clean the grass off the removeable screen in the engine compartment?"
He was right. I cleaned it, the problem went away and I learned something.
Thought it might be worth mentioning.

I’ve temporarily removed the shrouds from the engine bay. It helped enough I can mow without the high temp light coming on but it didn’t do a lot.
 
   / Kubota diesel overheating. #99  
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.
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.
 
   / Kubota diesel overheating. #100  
My quick thoughts. Many times, taking the thermostat out will allow too much circulation. Water moves too fast thru the radiator and cannot cool enough. Slow climb to overheating. As was mention somewhere in the first 10 responses, make sure you can see thru radiator fins. Having the fins look clean but having Dusty dirt between the fins will not allow air to pass thru. Blow water in the opposite direction that the air passes thru. That's all I got.
 
 
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