Mowing Kubota diesel overheating.

[4570Man]

At that many hours I'd pull the radiator and physically clean the outside. Flush the fins out of debris. They make coil cleaner in a spray can for your Home AC unit which are aluminum. Its just a heavy degreaser but pretty cheap. So Purple Power or Simple Green might do the trick too. My Old Man would mix up some weak muriatic acid in a garden sprayer for coil cleaner. Probably some benefit to a cooling system chemical flush and a new thermostat with that many hrs.

Not sure how exhaust flow is laid out on your ZT. I had a Cub Cadet riding mower that had a crack in the exhaust that bled enough extra heat that it would vapor lock after awhile.

My Kubota B7800 has a creeping heat issue too but only has 800hrs on it. I keep the radiator flushed out with a garden hose a few times a season and carry a big paint brush to keep the cowl screen cleaned off once an hr. I move 5 acres of weedy "yard" and there is a lot of fluff that accumulates. I think airflow will be the biggest issue.

My buddy had a trackhoe that was overheating because the exhaust was leaking into the enclosure. I tried removing the enclosure which helped a little bit but not much and the exhaust looks good.

 

[johndinino]

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 t

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.

Could be you are running lean on fuel. Most any motor will run hot after a bit if it does not get enough fuel.

 

[CoyPatton]

Water easily flows through it from a water hose.

Water freely flowing from one hose port or cap opening to other hose port, tells you absolutely nothing about water flow throw the small passages of then fins were cooling occurs.
I also noted that this is your response to seeing light through the air passages openings between the fins. All that dirt and dust and clippings when you mow are either pulled or pushed by the fan through the radiator. I would mot be s bit surprised to fund that you have issues in the fins—water passages or air passages if not both. Same symptoms with mo thermostat indicate one or both are issues.

 

[Alan46]

No, it don't Just went through that on another thread. Ordinary distilled water is the best heat transfer medium there is, much better than antifreeze in any concentration. The ONLY thing AF is good for is below freezing temps. Far as corrosion goes, add a bottle of Purple Ice or Water Wetter to the water. That gives it corrosion protection. That will cover the infamous water pump seal that don't exist any more too.

As a side note, race car drivers don't use AF at all, just plain distilled water with Purple Ice or Water Wetter.

Don't believe me, Goggle it up and find out for yourself.

Your so right! In my 650+HP mustang drag car, distilled water, water wetter, 160' thermostat and aluminum radiator never got over 195 after a pass!️

 

[fireball1800]

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.

My bx25 3cly diesel does the same thing. Running at 3000rpm mowing on a 80 degree day in a dusty field the temp creeps to high in about an hour. Don’t know about the zx, but On the BX there is a pre screen in front of the rad that captures a lot of fine particles. This comes out the top to be cleaned. I have to regularly pull that and wash. Doesn’t take much dust and debris to restrict the airflow.

 

[sixdogs]

I have a 725D so am familiar with your setup. My advice is to call the company and ask them. They are very helpful, have been down this road before and can be very helpful. They have real tech people either on the phone or by email and not just flunkies. They are a great company.

It's worth noting that the coolant should likely be flushed and cleaned since stuff builds up and can restrict passages. Use the correct coolant snd there's serial number break on coolant specs. Second is that the radiator fins can be restricted and topic not fully know it since all the grass blows there. I blow out my fins every time I mow.

Hope this helps.

 

[the old grind]

Reversing a fan blade won't change the direction of flow, only reduce efficiency due to the curve of the blades.

A coolant reservoir should be 'empty' when cold and 'full' when hot.

Diesels don't run 'lean'. They can't! With no throttle plate the engine draws its air by volumetric efficiency at a given rpm. Whatever fuel is injected determines power and rpm under load. There is no fuel/air ratio to be measured or calculated.

How hot when operating and how tall is what's being mowed? Lush green stuff (weeds, etc) demands more power than if dried out a bit.

 

[CausticUrbanCoast]

I’ll look into 3rd party options for a radiator. I put one on my b7200 for under $200. I don’t think there’s a radiator shop in town. I’d have to go to the next town over 30 miles away. If I can find one fairly affordable for a new one I’d rather do that.

Cheapest will be from a reefer unit or a bobcat style welder. The reefer units would probably be the easiest to find.

 

[macdoesit]

As mentioned before, can you see light thru the rad from top to bottom, if not use air hose and clean from fan side thru rad. Does water run freely thru the engine block.

 

[ho72]

My Kubota B7100 (ancient, I know) was overheating due to the way I was cleaning the radiator, i.e. flushing it externally with a garden hose. The hose removes some but not all of the debris. The residue turns to sludge and then dries and hardens. Rinse, repeat, and before long you've got a radiator that won't flow enough air. Pressure washing fixed it and from then on I did my radiator spraying with an air hose.