Mowing Kubota diesel overheating.

[4570Man]

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.

 

[ptsg]

Maybe it's time to flush the entire cooling circuit. The radiator maybe clogged inside or something.

 

[Midniteoyl]

You did make sure you could see light through the radiator, top to bottom, correct? Barring that, I would agree that a proper flush is in order next.

 

[4570Man]

You did make sure you could see light through the radiator, top to bottom, correct? Barring that, I would agree that a proper flush is in order next.

Water easily flows through it from a water hose.

 

[Williy]

Do you have the right mix? water alone will
not work and anti-freeze needs water to work

willt

 

[4570Man]

I’ve replenished what was lost removing the thermostat with straight water but it was a good mix before that.

 

[RickB]

How many hours on the machine? If over 500, pull the radiator, remove the shroud and thoroughly clean the core including the corners. Install a new stat.

 

[5030]

Do you have the right mix? water alone will
not work and anti-freeze needs water to work

willt

Actually, distilled water has the best heat transfer ratio of anything. AF is only needed when the ambient drops below 32 degrees (F).

 

[4570Man]

How many hours on the machine? If over 500, pull the radiator, remove the shroud and thoroughly clean the core including the corners. Install a new stat.

2600.

 

[Unclewillie]

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.

had a friend purchase on of those that's cooled by a belt he got it cheap cause it was overheating and like you trying / tried everything except replace the belt and in this case that's all it was. The sides of the belt wore slick and didn't grab as designed.

 

[dodge man]

Water pump checked yet.

 

[4570Man]

Water pump checked yet.

It seems to be circulating otherwise the radiator wouldn’t be hot. At least that’s my logic.

 

[Beaver Cove Deere]

Actually, distilled water has the best heat transfer ratio of anything. AF is only needed when the ambient drops below 32 degrees (F).

Wrong. AF also raises the boiling point and helps the seals. If the engine has liners it helps the water side of them as well from pitting.

 

[5030]

Wrong. AF also raises the boiling point and helps the seals. If the engine has liners it helps the water side of them as well from pitting.

Whatever you say boss but I suggest yo do some research on the subject. I said distilled water, not tap water, distilled has no mineral content. The only seal is the water pump seal and modern pumps use a metal seal.

Care to provide a link to substantiate your claim? Maybe I should say, can you provide a link?

 

[Midniteoyl]

Wrong. AF also raises the boiling point and helps the seals. If the engine has liners it helps the water side of them as well from pitting.

Straight water cools better, usually. You raise the boiling point of water chiefly through increasing the system's pressure, controlled by the radiator cap. Glycol adds very little to raising the boiling point (~10-15*F @ 50/50) and so is used mainly to lower the freezing point. Glycol mix also lowers the specific heat capacity (about 20% less @ 50/50) than pure water. That means as the 50/50 mix passes through the cooling system it is only able to carry away ~80% of the heat from the cylinders than pure water would be able to.

Pure water is generally teamed with a rust inhibitor additive and a cooling system booster that reduces the surface tension of the coolant, like Water Wetter and Purple Ice.

 

[the old grind]

Replacing AF mix with straight water won't be 50/50 for long. Actual working load and ambient temps haven't been specified. Doesn't matter what the engine is in as much as how hard it's used and other operating conditions/details. Some flow isn't the same as prescribed flow of coolant or air. I wouldn't hang the bird on coolant ratio. My philosophy is that if there is more than one possible cause several are are in effect. Lets find 'em all.

 

[Midniteoyl]

Replacing AF mix with straight water won't be 50/50 for long. Actual working load and ambient temps haven't been specified. Doesn't matter what the engine is in as much as how hard it's used and other operating conditions/details. Some flow isn't the same as prescribed flow of coolant or air. I wouldn't hang the bird on coolant ratio. My philosophy is that if there is more than one possible cause several are are in effect. Lets find 'em all.

Just clarifying a common misperception, not saying that is 4570man's problem.

 

[4570Man]

We’re about to find out what straight tap water does. I’m going to go flush it with a water hose and mow some more. It still doesn’t have a thermostat in it. I’ll have to get one tomorrow.

 

[Menagerie-Manor]

Wrong. AF also raises the boiling point and helps the seals. If the engine has liners it helps the water side of them as well from pitting.

With regard to actual heat transfer H2O is the best as he stated, cooling systems regardless of application are de-rated as the percentage of Glycol increases.

 

[4570Man]

Well this might not be the by the book method to flush a cooling system but it looks pretty flushed and confirmed the water pump is working.