Kubota tractor overheating when fan replaced to electric. (Kubota G1900S (D722))

[jacoBiceps]

I assume there are covers off so how/where does the radiator draw air from? I don't like all the electrical right in the path of the radiator. How is a person supposed to properly clean it?
Chaff can really be deceiving, and the newer style radiators are a PITA to clean. Get some coil cleaner and wash it well then carefully blow it out with an air hose. Then do it again, Then, run it hard to make sure the radiator is dry before putting it back in the dust.
Like others have said, I would put everything back to square one after a thorough cleaning and see if it makes a difference.
As far as water pumps, they can get weaker from worn vanes and can even go bad. But usually, you can hear or feel a bad water pump.
Get back to square one and start with the simple stuff.

It pulls air from the back of the tractor, where your legs are. Kubota claims the reason they did it like that is so on hot summer days, you wouldn't be getting blasted with hot air.

 

[dvcochran]

It pulls air from the back of the tractor, where your legs are. Kubota claims the reason they did it like that is so on hot summer days, you wouldn't be getting blasted with hot air.

Is that an addon speed controller in the photo?

It pulls air from the back of the tractor, where your legs are. Kubota claims the reason they did it like that is so on hot summer days, you wouldn't be getting blasted with hot air.

Is that an addon speed controller in the photo?

 

[GreensvilleJay]

yes, he added the PWM speed controller to slow down the fan BUT not all '12 volt electric motors' respond well to PWM.
I'll assume he bench tested it for 5-6 hrs, different speeds to be 100% sure it would work as required. If the controller isn't rated for 30 amps ( x2 the fan's spec) AND mounted on a big steel plate or in the airflow, it can overheat and go 'funny'.... seen THAT several times in the past...

 

[jacoBiceps]

Is that an addon speed controller in the photo?

Is that an addon speed controller in the photo?

Yes

 

[SDT]

I just recently replaced my tractors belt drive fan for an electric fan and it yielded the opposite effect I was hoping for. Instead of it keeping the temps lower, it started overheating the engine. The fan I'm using is a Spal 30100435. It's a 10 inch fan, and fits pretty well in the radiator shroud. I did have to do a bit of jerry rigging to get it to fit, but nonetheless, it fits. I checked the thermostat and it opens like it should. The radiator is fine to my knowledge, as it was working fine before I changed the fan. It is still pulling air like the belt drive, and it is moving 10x as much air, but the engine is getting hotter than normal. Now, I know you're asking why would I change it if it wasn't broke. Well, I plan to add more power in the future by adding more fuel by advancing the timing on the pump, and also adding a turbo. I wanted cooling to be very efficient before messing with the engine. If anyone has any clue to why this is happening, any help would be super appreciated. I have asked many people what the problem could and they all were speechless.

Caveat: Have not read earlier responses.

Return it to OEM specs and see if the overheating issue goes away.

If so, you've found your problem.

 

[Joisey]

All or most of those electric fans are not what they are cracked up to be, at least in my experience. I built a 1948 Chrysler Winsor, and put a 350 hp small block in it. (I know, a small block Chevy in a Mopar but I could not get a 440 to fit). When the biggest baddest elec. fan did not cool, I did the extra work making a shroud and installing a belt fan. From then on it ran cool as a cucumber. Just my 2 cents..
rr

My 2006 GMC Sierra 4wd 5.3 high output came stock with 2 electric fans. One ran when the air conditioner was on, the other if temperature exceeded a set mark. In 160K miles, I heard the second fan come on once, I was stuck in traffic in 100 plus degree heat with the air on high for almost an hour. The temp gauge never strayed a half of a needle above or below center, no matter what I was pulling or the temperature outside. There is more to making an electric fan work than just slapping one on and connecting a wire or two.

 

[cthomas]

it'll be 6 or 7 by the end of the day !
Seems Buffalo's being dumped on ,'lake effect', hehehe...
BTW Never understood the need for a diesel powerd $$$$$ lawn mower....
When asked if I wanted the MMM for my BX23S I said I can buy 4-5 beater riders for the price and I'm still using the 20 year old Cub cadet that I paid $220 for....

Yes, but I can mow the lawn in an air conditioned cab with radio on and a beer in hand.

 

[cthomas]

If I remember right the mid 80's Audi 5000 had 2 engines both 5 cylinders(2.2 liters) with a radiator at a 30 degree angle behind the drivers head light. The NA and the turbo used the same radiator, but the turbocharged engine also had a additional radiator(no fan behind it) plumbed into the coolant system. This additional radiator was the size of a heater core and mounted behind the grill. Is it possible to do the same on your tractor? If your doing all this just for the sound of a turbo have you thought about a battery electric vehicle pedestrian noise maker?

 

[JerryMT]

Pictures

There's your problem. You buggered up the shroud! the tip of the fan is working in separated air. That shroud's shape is important.

 

[RBsingl]

At 180 watts (or 108 since both numbers appeared in the thread), that electric fan motor is capable of developing a small fraction of a horsepower and is probably just too small for the job compared to the mechanical fan. If the electric motor were 100% efficient, and it is NOT, then it could develop just under 1/4 HP at a 180 watt draw. Electric vehicle fans tend to do a poor job of working against high back or suction pressure and airflow efficiency drops very quickly under these conditions.

Cars in the 300HP range get away with a 500-600 watt fan BUT they have a large free airflow radiator and shroud system that was designed from the start for the electric fan. And most of the time the airflow is provided by high road speed, unlike a tractor they aren't running for long periods of time at full power and 2 MPH.

Rodger

 

[GreensvilleJay]

re: is probably just too small for the job compared to the mechanical fan.

not necessarily. So far ZERO info on the CFM the mechanical fan setup actually produces. The electric one has a spec of 802CFM. It'd be nice to see the spec for the OEM fan setup, only then can we compare 'apples to apples'.

 

[RBsingl]

Jay,

For the CFM number to be comparable, they would have to be specified under the same conditions. If Kubota engineering was willing to share the rated CFM of the stock mechanical fan it would be the actual airflow within that cooling system at a specified (generally rated) RPM. The aftermarket electric fan CFM static flow spec is generally far greater than what it will actually do with the real world pressure drop as part of the actual screens/radiator/shroud in this actual application.

Low power fans can produce very large airflow when there is negligible flow resistance but fans designed to have less performance drop under high flow resistance will typically use more aggressive blade geometry and often a higher RPM motor.

One of the alternatives to clutch type fans used by some of the automotive companies in the 70s were "flex fans" with blades that became less aggressive at high RPM to reduce noise and power draw. And electric fans are great in a lot of applications where packaging and cost are prime considerations but for this tractor application, a proper mechanical fan setup is still the most practical. If someone has a tractor dyno handy, do a very fast run with the mechanical fan mounted and removed to see how much HP it takes at rated RPM and I expect most would be surprised by the number but it takes a lot of power to move air with the airflow resistance of the cooling system. I remember seeing the specs for my GMC diesel pickup and the fan consumes close to 15 HP at governed RPM with the electric fan clutch fully engaged. The smaller fan on a Kubota tractor isn't close to this but it will be a lot more than the actual developed HP of a small electric fan motor.

Rodger

 

[GreensvilleJay]

If I was really,really, really curious about this all I'd need is the fan dimensions and RPM. One of my clients made fans (ok huge 'industrial' ones ) but he gave me several programs used to design them. That code is on an old Windows98 machine 'somewhere' in the basement,yeesh gotta be 2 decades old... At the time we were both intersted in modifying the code for variable pitch.... Probably some fancy 'online- fill-in-the-blanks' ap available these days....

 

[RBsingl]

It would take a complex set of inputs to accurately model airflow under different air resistance and RPM conditions. Blade geometry is critical and can be optimized for many parameters such as quiet, low power draw, high low static airflow, low performance drop under high static, etc. but not simultaneously for all of these parameters. Blade contour, edge "finish", shape and finish of frame/shroud can all create dirty airflow under differing airflow conditions.

Kubota and their supplier would have spent some quality design time choosing the proper setup, aftermarket setups aren't so carefully match making Bona Fortuna (good luck) a factor in typical user mods. The tractor was designed as a holistic system with multiple parts and subsystems working together, user mods that ignore this fact often result in sub-optimal results.

Below is a typical graph of real world performance for an electric fan with static pressure on the Y axis and delivered airflow on the X axis. Of note is that there is a rapid dropoff in delivered CFM which falls rapidly reaching cutoff at a fairly low back pressure. And the relationship lines aren't straight because of the interactive effects within the system. Axial fans will always have a fast drop in performance under increasing back pressure but they can be designed to work sufficiently under these conditions which is how Kubota set up the original cooling system. Centrifugal blowers can be designed to deliver a lot of CFM under high back (or intake) pressure but they aren't really practical for this type of cooling system.

Rodger