This article is the third in a series that covers off some basic servicing procedures for your Kubota. Earlier articles covered air and fuel systems. In this article we touch on your Kubota’s cooling system:

• radiator cap
• cleanable mesh screen
• hoses (top, bottom and bypass)
• radiator fins, body, shroud and fan blade
• overflow tank and drain petcock
• contents of the radiator

Radiator Cap
Your Kubota is designed to operate with a pressurized cooling system, same as you typically find on a car or truck. The pressurization raises the boiling point of the coolant so it’s important that it hold pressure.

Check the cap – it should be rated for 12 to 15 lbs of pressure. If you have a coolant pressure testing system, pressurize the cap and see that it holds at the indicated pressure. If it slowly drops, then replace the cap. If you don’t have a tester or access to one, then inspect the cap, its spring and rubber sealing gasket. If the gasket is torn, or as is often the case, chipped, replace it. If the cap wobbles or doesn’t seem to engage snugly with the neck of the radiator, replace it. It’s money well spent to prevent a costly engine repair.

Making sure the pressure on the rad cap remains steady

Clean that Screen
Most B, L, L-1, Grand L, and M Series Kubota’s have a removable mesh screen installed in front of the radiator. The problem is, most owner/operators don’t even know it’s there. These screens are discreet and often just look like part of the radiator which explains why they are often not removed and cleaned.

The fine screening is designed to keep debris out of the radiator fins and its this screen that needs periodic cleaning and blowing out, particularly if you do a lot of mowing or rough cutting. The newer BX models are designed with the radiator mounted more mid-tractor and the fan blades direct air back through the radiator. This keeps the radiator and cooling system on a BX cleaner than earlier L Series Kubota’s.

To clean this screen, find the hold down bolts, loosen them off and withdraw the screen and frame. Using some air pressure, blow the screen out and blow off the exposed front of the radiator fins then reinstall. Simple!

Hoses
What we are looking for when it comes to hoses is feeling around for any softness or mushiness – a weak hose. Push your thumb into the middle of the upper and lower hoses feeling for softness. The lower hose may have a coiled spring inside it, so workaround that. Twist and pull on the hoses slightly where they are held in place by the hose clamp. Any tearing? Do you hear ripping?

Test rad hoses by feeling for soft spots, twistly slightly and looking for tears or listening to ripping

Early L-Series Kubota’s had fabric covered hoses. If your tractor still has these on the hoses, it’s time to replace them. The hoses in general should feel supple, yet firm. They should not have bulges or soft spots. If they look original and the tractor is 10 years old, replace them.

Don’t forget to take a look at the bypass hose if you have an L-1 or Grand L Series either. Those little 4″ long hoses can go bad too. Get down on the shop floor and look up from the underside of the radiator if your tractor has a drain petcock on the right hand side of the frame. Chances are there is a hose running along the inside of the frame rails from the left hand bottom side of the radiator to the back side of that drain petcock. Those who own an L1802, L2002, L2202 gray market Kubota will know how difficult this little hose can be to change out! Seems like Kubota had a hose and then built a tractor around it.

Belts, Thermostat and Water Pump
The fan belt is a fairly easy check over. Push down in the center of the belt to measure deflection. Should be 1/2″ or so of give. Tight, no slack. Roll the belt over and check the v-groove side for cracking and glazing. The belts should be replaced if you notice fraying, cracks or excessive glazing. If it makes noise when the tractor is running, replace it as well.

The belt is hard to get to so we are using a socket extension to test its deflection.

The water pump should be visually inspected for any leakage from either the pulley bearing area or from the gasket/front engine case area. On a Kubota you’ll know when the water pump or thermostat require replacing as the engine operating temperature will ramp up very quickly and you’ll be hemorrhaging coolant. Shut down and investigate ASAP!

Rad Fins, Body, Fan Shroud and Blade
Visual inspections here can really save on expensive repairs and down time and take only a few moments once or twice a season.

When blowing out the mesh screen from the earlier step, also blow out the radiator fins. Blow from the engine side to the grille or front of the tractor. Take a look at where the fins attach to the top and bottom tanks of the radiator. Corrosion showing here means a repair is looming.

The tanks of the radiator should be of normal size, not distorted or expanded which may indicate previous expansion freezing due to a weak coolant mixture. Grasp the fan shroud and make sure it’s firmly attached to the radiator body. Align it if it’s contacting the fan blade. All Kubota tractors employ a flex style white plastic fan blade. Visually inspect for cracks on any of the blades. Clean the fan blade if yours looks black!

Overflow Tank and Drain Petcock
Quick visuals are all that is required here. Check inside the overflow tank for sludge. Unclip the reservoir and clean it out if it looks ‘muddy’ in there. Top it up with new clean 50/50 coolant mix. Open the drain petcock (have your catch basin ready below) to discharge any rust or heavy deposits that have settled into the lowest part of the system, the drain. Removing these annually will keep the cooling system in top shape.

Open the overflow tank up and check for sludge or muddy coolant

Radiator Contents
If your Kubota is operated in a warmer climate where the possibility of a freezing temperature is remote and you’ve been running water alone in the cooling system, now is the time to upgrade to a proper 50/50 glycol water mix. Why? Well it has a higher boiling point, has anti-rust properties, lubricates water pump bearings and is safer on gaskets than water alone. But it too must be changed regularly to ensure continued engine protection.

All too often in the service department we see needless upper cylinder head damage caused by overheating, porous cylinder head gaskets and blown expansion (frost) plugs. These are expensive repairs that absolutely could have been avoided by proper radiator cooling management. Those early Kubota L Series tractors had a whistle installed on the overflow tube to sound off like a train when the radiator was run completely dry. If you’ve ever heard that whistle think of it as the sound of money being spent in my service bay! Point being – don’t ever let that whistle blow.

Checking the coolant frequently is a good habit to get into

Check the contents of the rad before operation each day. Kubota recommends an annual flush and refill of the cooling system. Don’t operate on water alone and don’t operate on straight anti-freeze/coolant. A 50/50 mix is recommended. If the coolant doesn’t look green, has a brown color or looks like mud, it’s been too long since it was serviced. Up the diligence here as this one is pretty serious.

Summary for Servicing your Cooling System

• check radiator cap by seeing if it can hold pressure
• remove and clean mesh screen in front of radiator
• test rad hoses for softness and tears
• test fan belt for deflection of not more than 1/2″
• check fan belt for cracking, glazing or fraying
• blow out radiator fins and visually inspect for corrosion
• check overflow tank for sludge or deposits
• make sure your radiator contains as 50/50 glycol water mix

Service Department Vic

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Kubota Servicing 101: Part 1 – Air Filter
Kubota Servicing 101: Part 2 – Fuel Filter
Getting to Know your Kubota’s Clutch
Forum: Service, Repair & Maintenance

We continue our multi-article overview of basic Kubota maintenance by taking a look at the fuel system. In Part 1 of this series, we covered off air filter servicing, so have a look if you have not already.

2 Styles
Depending on your model of Kubota, your tractor will be equipped either with a spin-on cartridge style fuel filter (like the L175, L185, L1500, etc) or it will have the more popular paper element/sediment bowl style of fuel filter.

Spin-On Style
Can’t get any easier than this! Turn off the fuel petcock located on the left hand side of the fuel tank. Next, locate the filter assembly. It looks like a small oil filter but instead is mounted straight up and down, unlike the oil filter which is mounted sideways and more to the front of the engine on your Kubota.

A spin on fuel filter

Place a catch basin under the filter and loosen it off. It’s going to come off full of fuel so be careful. Once removed, clean the underside housing off with a shop rag. Check the old filter and make sure that the sealing o-ring came off with the filter. Sometimes they get stuck to the underside of the housing and if you forget to fish it out, you’ll have a fuel leak from hell until you figure it out!

Here’s something that will spare you bleeding injector lines after a fuel filter change – spin on the new fuel filter but just leave it loose by a thread or two. Reach over and open the petcock shut off to allow fuel to fill the filter. It will fill all the way up and run over the sides of the filter down into your catch bucket below. At this point, tighten the fuel filter up and wipe off any spilled diesel. Done. Easy!

Sediment Bowl Style
The sediment bowl and element filter is the more widely fuel filtration system used by Kubota. Even the early Kubota B Series B5100, B6100 or B7100 and gray models B5001, B6001 or B7001 had them. Here’s how to service this style of fuel filter system.

Close the fuel petcock located just above the sediment bowl. Place your catch basin under the filter and loosen off the large retainer ring holding the sediment bowl assembly on. This may be tight and unless you have the correct Kubota service tool for this task, you may employ a flat blade screwdriver and a brass drift to nudge that ring loose.

Sediment bowl style fuel filter system

After loosening, the bowl will drop bringing the filter with it. If the filter hangs up in the housing, simply remove it. You’ll notice that the sediment bowl seals with a larger rubber o-ring as shown in the exploded view below.

Inspect this o-ring in the assembly

Inspect the filter’s o-ring and make sure it’s not nicked or damaged, especially during reinstall. If the filter came out in the bowl, use a set of pliers to carefully remove the filter from the sediment bowl, and be careful here – those sediment bowls are very prone to cracking if you pry on the filter to remove it from the bowl. I have seen Kubota fuel filters jammed so hard into the sediment bowls that the filter breaks apart trying to remove them! Under the filter will be a small spring. Make sure it’s replaced when reinstalling the new filter.

Next, clean out the sediment bowl with varsol or in your parts cleaner. Clean the metal tightening ring and wipe the bottom of the sediment bowl housing clean before reinstalling the fuel filter element and bowl. As we covered before with the spin-on type, let fuel spill out of the sediment bowl before fully tightening the ring to avoid having to bleed the injector lines.

Summary for Servicing your Fuel Filter

• determine if you have a spin-on or sediment bowl (more common) style of fuel filter system
• place fuel catching bucket underneath filter assembly
Spin-On Style
• spin-off making sure sealing o-ring came off too
• replace with new filter
Bowl Style
• close fuel petcock
• loosen large retainer ring
• drop bowl and carefully remove filter if necessary
• inspect assembly o-ring for damage
• replace filter on top of small spring
• screw on new filter but leave loose by 2-3 threads
• open fuel petcock
• let fuel fill filter and run out and down into your catch bucket
• tighten fuel filter for the remainder

If you’d like to learn more, head on over to Part 3.

Service Department Vic

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Kubota Servicing 101: Part 3 – Cooling System
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First day of fall. The shelter belts are thinning, leaves yellow and the air is a bit crisp in the morning. Winter is on the horizon! With that in mind, let’s take a look at a couple of important fall service requirements for our Kubota tractor, and let’s do it today before there is a foot of snow on the ground.

If you haven’t discovered it yet, that little orange Kubota tractor of yours can take a lot of service neglect and still perform remarkably well. I’ve seen tractors here in the service department with fuel filters crammed with crud, the air filters caked with dust and seed and radiators with little more than creek water and mud in them. I am always amazed that in spite of that, these Kubota tractors keep starting and running. A testament to their superb engineering and design, regardless of age. That being said, we all know that our favorite orange tractor does need love every now and then, so with that, this article is the first in a multi-article set that covers basic Kubota servicing.

Small But Important
The single most important service item for your Kubota is the air filter. Diesel engines consume major amounts of air and all of it passes through that paper and mesh filter, so it has to be clean.

Remove air box end cap

Locate the air box, and remove the snap on end cap. Inside the end cap you will see a silver “cup”. It’s inside here that you’ll find the first of what is usually a pile of dirt, bugs and debris. Strangely enough most owners don’t even realize that this cup is itself a filtering system, and subsequently, this area can be overlooked. Tap out the dirt and then replace the cup inside the end cap.

Clear out bugs and debris here - we've already clears ours in this picture

Next, remove the air filter element paying careful attention to the rubber rimed washer on the end of the wing nut. This 10 cent item has been the cause of more than one engine failure over the years. That rubber rimmed washer must be in perfect shape when it seals to the metal end of the air filter, otherwise all the dirt that you saw inside the silver cup gets ingested right into the engine, bypassing all the filtering! Assuming it checks out OK, remove the air filter element.

Make sure this washer seals against the filter snugly

Cyclonic Action
Kubota engines employ cyclonic air filtration on all their diesels and for good reason – the air flows around the filter at high speeds, shaking out heavier particles (sending them to the silver cup we looked at earlier) and then filtering the finer particles through the medium of the filter before intake into the air plenum.

Rap the filter lightly on the work bench to dislodge any heavy particles, and then with a blow gun and care (under 30 PSI), blow out the element. It’s also acceptable to wash the paper element out in a bucket of warm water, rinsing back and forth until the paper is clean. Don’t blow air over it after washing, just let it stand and dry before reinstalling.

A Common Misconception
Everyone seems to think that you have to replace the air filter every year. Not so. With frequent cleaning and blowing out (minimum twice per operating season), you’ll get five years or better from that Kubota cartridge. Now you know why that Kubota brand filter is $37 and the NAPA one is $18.

Our cleaned up filter

OK, the filter is clean, lets inspect the paper for any breaks or tears. Use a Mag light or a small fluorescent trouble light and really look that element over. The slightest break in the paper and it’s garbage. Don’t cheap out here! There are things you can skimp on,and this air filter is not one of them.

Before reinstalling the filter, take a shop rag and wipe out the inside of the air canister assembly. Reinstall the element using the wing nut and rubber rimed washer, snap the cap and debris cup back on – we’re finished here.

Summary for Servicing your Air Filter

• locate the air box
• remove the push-on cap at the end of the air box
• inspect and clean out silver cup on the inside of the air box cap
• inspect washer and wingnut assembly for fit against metal base of air filter
• remove filter cartridge and clean with light air pressure or warm water letting stand to dry
• inspect filter for tears with fluorescent light if available
• clean out air box assembly
• reassemble filter, washer, wingnut, cup and cap

If you’d like to learn more, head on over to Part 2.

Service Department Vic

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Kubota Servicing 101: Part 3 – Cooling System
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