Mowing Kubota diesel overheating.

[lineman1954]

peace of mind..flush block, radiator, change thermostat......check oil for any contaminants ( head gasket )

 

[English Rugby Fan]

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 had the same issue with our 2006 Grasshopper 428D. Creeping water temp. After all the work that’s been suggested here and I can only assume it’s one of those answers ?
Ours had a new clutch did all the maintenance on the rad literally everything and all came good.
So good luck, can’t think of anything else that might help!

 

[blackvette]

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

That is a fact. Nothing beats water.

 

[blackvette]

I would replace the radiator. Over time , the thing gets dirty inside, and the capacity to disperse heat diminishes, at the molecular level…..especially a copper radiator…..

 

[mark74080]

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.

Replace the sending unit. It's cheap and quick.

 

[CausticUrbanCoast]

Diesel and petrol engines use additives for different reasons.

However, I see that it has not been asked if the fan blades have damage or even worse was put on backwards? The only image has the fan running.

The question about the worn belt was a good one as well since the fan will slip.

 

[swines]

Have you checked the radiator cap to make sure it is sealing correctly? If the radiator cap is losing pressure, the system will not cool correctly. The cap may not be leaking, but it can still not hold pressure to seal the system.

 

[4570Man]

I premix/label for my climate at 50/50 with distilled water that I buy and use weekly along with drinking water and for $.89/gal. Reading labels for yrs it's stuck in my head that 33%-66% is recommended. 33% AF for warm climates, and I've read somewhere that 66% AF may be indicated for diesels to minimize cavitation an/or cyl liner wear where applicable.

I also use a refractometer to gauge acidity. Remember when the service station guy would use one before recommending a change? ('50s, '60s) Modern AFs (yellow/green, orange, 'gold') are typically formulated to protect alum components in car/truck engines from galvanic corrosion. The more noble alum will scale or corrode as coolant ages. A tractor that has no alum head, block, lower intake man, water pump, etc getting coolant flow can do ok with the old green stuff.

I can't imagine a cooling system being so fussy about the exact mix to do its job well. That said it's not just the fins that can need cleaning. Got aluminum radiator? It could be scaled up on the inside. I agree with suggestions that a flush may be needed based on hours & age.

Yes it’s an aluminum radiator. Even before the overheating issues started its always been fussy about dirt in radiator. My tractor would work fine half buried in chaff but this would start gaining heat with 5 pieces of grass over the radiator.

 

[5030]

I'm thinking, being a lawnmower with all the grass clipping flying around, the rad may be plugged up at least partially.

If I was the OP, I'd either pull it and clean it or get a radiator Genie (Amazon) and clean it with that and do it regularly.

What I use on my farm tractors after running hay.

 

[CausticUrbanCoast]

Yes it’s an aluminum radiator. Even before the overheating issues started its always been fussy about dirt in radiator. My tractor would work fine half buried in chaff but this would start gaining heat with 5 pieces of grass over the radiator.

Were you using an aluminum coolant additive (some ford trucks and other specialized vehicles require it)?