Mowing Kubota diesel overheating.

5030

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One item to be aware of (squirreled away in the back of your mind) is that all Kubota engines are well noted for popping head gaskets when overheated. For some reason they do that when they get hot so it's imperative to keep the heat under control at all rimes.
 

art

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I would have the injectors tested. When one doesn't work right it causes a cylinder to run dry and cause a over heating problem while running extended times.
 
  
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4570Man

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You didn’t say what the actual temps are. Didn’t you use your laser thermometer on the head, block, oil pan, and radiator tanks? Always look at the simple solutions first. Maybe the temp gauge or the sender is bad. I’ve seen late model machines de rate and refuse to run repeatedly, when nothing is wrong, but a brain cramp. Bad sensor S, but no actual problem. A million hours of mechanic time is wasted every year in this country on computer and sensor glitches on engines with no underlying mechanical issues. Not to suggest you are dumb or anything, maybe you did confirm that the engine is too hot with your temp gun.

About 210 after I got it cooled down some and 230 before that.
 

Green Sunshine

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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.
 

Green Sunshine

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I had a similar problem with my Montana diesel tractor and what I finaly discovered was that the cooling fins in the radiator were clogged with built up dust and tiny peaces of grass etc. this was only at the bottom 3-4 inches of the radiator cooling fins so it was hard to see it. Looking at the radiator it appeared clean but uppon very close inspection I spotted the clogging in between the fins, after cleaning that out with some degreaser and water pressure the overheating problem went away. Now I keep a close check on that so it wont happen again.
 

TBotNik

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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 flushed the cooling system? Sounds like it needs it! Supposed to flush them every 2-3 yrs!
 

dodge man

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I would have the injectors tested. When one doesn't work right it causes a cylinder to run dry and cause a over heating problem while running extended times.
I’m pretty sure that’s not his problem, he would notice a cylinder dropping out also. The problem occurs when a injector over fuels a cylinder and causes it to get hot.
 

ptsg

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Being that the OP already did pretty much everything possible on the cooling system, I'm now start thinking about something else. Something on the mower deck or transmission can be putting an extra load on the engine causing it to overheat or something.

What's the condition of the air filter?
 
  
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4570Man

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I took the radiator out and cleaned it. It looks pretty clean but on close inspection there was quite a bit of trash in it. I’ve cleaned it, put a new fan belt on, new thermostat in and I’ve got some chemical radiator flush to go in after I put it back together.
 
  
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4570Man

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IMG_0228.JPG
 
 
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