Overheating issue on L series verified

ShaunRH · Oct 23, 2014

There are a few threads on some of the smaller B & L units overheating when mowing. I can personally verify this and attest to it happening and the cause, and the resolution.

The Incident:
I was following the standard advice when mowing my 6 acres last week. I have a native grass/weed that forms downy soft tufts on long shafts. These tufts come apart and clog up the front screen so I had to clean that screen every hour. What I was NOT seeing is that some of it got through the screen and started plugging up the radiator. You don't see anything on the front of rear of the radiator, it is actually in the fins/corrugations themselves.

The way it plays out is that you see a slight temperature increase over time. I had been mowing over the course of two days and near the end of the work, my temps had gone from near the bottom to almost horizontal in the 'safe' zone. I looked at my gauges about every 10-15 minutes. I started smelling antifreeze and looked down at my gauge. It had gone from mid horizontal to maxxed out in less than 10 minutes.

I shut down the tractor and opened the hood. The safety boil over features worked perfectly. The steam generated by the radiator was pushed into the overflow bottle giving it a boiling appearance. It then escaped via the overflow tube and this gave my nose the 'heads up' that something was wrong with the cooling system.

I let it cool down and then restarted it to check for damage to the engine (thankfully none, no head gasket or other damage. Oil good, but it did suck the entire overflow contents back into the radiator!). I got more anti-freeze and filled the container. Further use sucked back in no additional fluids so it had only lost about a pint or so of fluid.

The Cause:
I investigated the issue while the tractor was cooling down. I found the front screen had very little stuff on it (I had just cleaned it 30 mins earlier) so then I looked in the fins. I could see the blockages, and it wasn't very much. About 1 out of 4 passages had some form of blockage, but very few had total blockage.

I got a small shop vac and blew out the radiator, back to front, and vacuumed it out from the front and then from what I could access on the back. A small cloud of garbage came out but it was enough to cause the overheat problem when the tractor is under load.

Restart with the radiator cleaned, even running under same load, showed the unit remained cool. So only a small amount of 'junk' in the radiator fins in capable of overheating the unit when working it under what I would call a normal load.

So part of this cause is design related to the tractor. The radiator is just big enough to handle normal workloads, so watch it when working the units hard. It is also subject to blockage due to the corrugated heat sinks between the fins.

The Solution:

Clean the front screen every hour when mowing.
Check the radiator passages every other front screen cleaning.
Keep something handy to blow or vacuum out the radiator, don't use compressed air, high volume, lower pressure air works fine.
Watch your temp gauge every 5 minutes or more often, it happened really fast from horizontal to max. I had just thought the elevated temperature was due to the day warming up.

Notes from the Experience:

There is also no overheat shut down safety. These engines are modern enough it should give a buzzer at the redline and shut down at a max temp. That's a $10 circuit that could save thousands of dollars in repairs, come on Kubota, you have safeties on everything else, this makes it look like you're wanting the units to damage themselves. What if my temp sender was malfunctioning? (it wasn't) Heckuva warranty repair bill if it was. I had thought there was an overheat warning, there isn't so that gauge is your only warning, keep an eye on it.
I have the gear drive L3200, it probably would've been more of a problem with the HST, both from a heating up perspective and an inconsistent speed operation since the pedal lets you control everything. On the gear drive you put it in gear and rev up to PTO RPM and let it go. Speed is controlled by what gear you are in. I mowed the lower stuff in 4th and it worked without complaint, the higher stuff in 3rd, much slower but it had the best cut. I ended off in 4th in some tough stuff so that added to the load on the unit, now I will never cut in 4th unless the stuff is under a foot in height or very thin.
While this incident was with the mower, I can assume the problem might existing with plowing, rototilling, even scraping/grading if you are getting enough junk churned up in the air. So be careful.

Word of learned advice, that temp gauge is your buddy, don't let it out of sight for long. There's not enough headroom in the cooling of these smaller units and no automatic shutdown. If you smell coolant, stop and check it out immediately!

Attached is a picture of the rig so you can see the setup.

Bulldog · Oct 23, 2014

Over the years of owning Kubotas I have always thought they could have done better on their cooling system. To me they seem to have just enough to keep the engine cool in normal situations. Add the smallest amount of trash on the screen and it will start warming up. All the IH and JD equipment I have been around don't seem to have this problem.

Here's a good example of why a Kubota will heat up before some of th others:

M 135X - 123 pto hp - 15.9 qt cooling cap.

JD 4440 - 130 pto hp - 36 qt cooling cap

Almost the same power but the deere has more than double the cooling system.

mickeyd · Oct 23, 2014

ShaunRH, I had exactly the same problem when my L3200DT had only 10 hours on it. Since then, I watch my gauge very closely and as soon as the needle gets to the center of the 'safe' zone, I stop the tractor and clean the radiator. What a pain!!

ShaunRH · Oct 23, 2014

Mine now has 18 hours on it, so it's in the same boat as yours mickeyd. I guess it's part of the 'learning the new tractor' experience. I just put this up as a warning to other new owners. It might make a good sticky for a new forum topic area... maybe "So about your new Kubota... start here!"

I'd like to replace that front screen with a more effective debris removal or capture system, just gotta work it out in my head. I'll let everyone know if I come up with something that works. Right now I'm thinking a material like womens stockings are made of over the screen as a temporary fix. A thin capture box would be better all the way around, something you could dump or clean from the seat... I had that rotary screen idea, maybe I should buff that out.

Don't know, yes it is a pain, but I can live with it. I just don't like blowing out the radiator all the time.

None of my old iron suffers from this problem. Very large cooling systems with radiators that have larger spaces between the fins. I wash it out when I hose down the tractors just to get the dirt and grit out of it. I've never had one of them overheat on me.

Bulldog · Oct 23, 2014

When I first got my L3000 is was doing the same thing your 3200 is doing. After I did the first service and switched to Amsoil my overheating issue went away and has not been a problem since. When the screen is loaded up it will run hotter than normal but it doesn't get to the point where I have to quit working. Not saying it can't overheat but I've been issue free since 2000.

Not trying to get another oil war started, just passing along some info.

coachgeo · Oct 23, 2014

Sounds like a rubber make shift shroud to isolate it from any outside air with floaties in it...... and a push or pull electric fan on the front or rear of radiator (which ever has most room).. sounds like the ticket. Or get your radiator multi cored?

ShaunRH · Oct 24, 2014

Well, the fan is direct drive off the engine. Engine running, fan turning. I'm used to that. Heck on my D-17, the fan is driven off the crankshaft! So, no, the fan pulls like gangbusters.

It's already heavily shrouded on the backside so it pulls through the entire radiator.

The issue really seems to be a function of very low headroom in the cooling system, it just doesn't have much excess cooling designed into it. This generates a smaller radiator and that nice looking front end, but seems to cause the heating issue.

So, at least in my head, you have to work on keeping debris out or increasing cooling, or both.

I could try adding an engine oil cooler, which might address Bulldog's point about changing out oil types. The motor is still in break in period so that's not helping things. Changing to synthetic would likely cool it down but arrest the break in process and I'm not sure I want to do that yet.

I do appreciate the ideas, so keep them coming. If I come up with something workable, I'll let everyone know.

dmanlyr · Oct 24, 2014

ShaunRH said:
INotes from the Experience:

[*] I have the gear drive L3200, it probably would've been more of a problem with the HST, both from a heating up perspective and an inconsistent speed operation since the pedal lets you control everything. On the gear drive you put it in gear and rev up to PTO RPM and let it go. Speed is controlled by what gear you are in. I mowed the lower stuff in 4th and it worked without complaint, the higher stuff in 3rd, much slower but it had the best cut. I ended off in 4th in some tough stuff so that added to the load on the unit, now I will never cut in 4th unless the stuff is under a foot in height or very thin.

QUOTE]

Actually, the HST would be very helpful in this situation. The pedal does not control everything, the HST still has a mechanical throttle lever. So, just like a manual, you set the throttle for the PTO speed and off you go.

Where the HST will shine is that you can slow down momentarily when in the higher grass, you are not forced to keep up the speed that is set by a fixed speed gear transmission. Hit the heavy stuff, let up on the HST pedal, and when out of it, depress the HST pedal. Far superior in unloading the engine easily when working over a manual.

Of course you can drop a gear on the manual, but do most do it for a short patch of heavy grass, or would most, just try to power thru and not be inconvenienced by having to shift for only 20 or 30 feet of heavier stuff..... just saying

Not trying to start a HST verses manual debate, it just seems that you are making assumptions that really do not pan out on the HST in real use.

David

ShaunRH · Oct 24, 2014

I think you are misinterpreting my comments on the HST use. My comments are that the HST generates more heat by it's very operation and function. It also places a larger demand of work on the engine (efficiency wise).

The HST is smoother, as you point out, but that comes at a price for heat. That slow down isn't the engine magically throttling down, it's restriction of the flow of hydraulic fluid and that energy must go someplace, back to the sump and to heat.

The DT version is more efficient at getting power to the wheels, but it's not as versatile as the HST, which you point out. However, in non-PTO implement operations, it's just as functionally easy to use a DT as an HST for most operations. This is because you put the tractor at idle and use the throttle pedal almost like an HST. In PTO ops, both have to be set to PTO RPM's and you can add a little speed to the DT with the throttle pedal but not much. Taking it off requires putting in the clutch and changing gears or throttling down with the main throttle, so the HST is more versatile in that degree, as you pointed out.

Again, my point was addressing the heat of the system, not how it's used during mowing, though I can see how you could read it that way. The "inconsistent speed" comment is referring to the very easy of changing speed that you pointed out, but the cost heat wise of doing that which I explained above.

I like both systems and see the advantages and limitations of both. If I had the money, and if the dealer had an L3200HST laying around their lot (they didn't) I might have gotten that, it would've been a toss up. I certainly don't mind the DT, I'm used to geared tractors. The HST is a good choice, but I see them as equal systems, not competitors.

To the heat point, I'd have to actually measure the case temp of a DT versus an HST to see if the heat assumptions I am making really pan out. They should as generally, more efficient = less heat. One of those laws of thermodynamics thingies...

Benhameen · Oct 24, 2014

I had the same issue with my L3800 while mowing some very high grass. Mine did get hot but not to hot, I shut it down and cleaned the removable screen then let it cool down for awhile, all good after that. I do keep a close eye on it now though and usually I will clean the screen any time I'm stopped.

dmanlyr · Oct 24, 2014

ShaunRH said:
I think you are misinterpreting my comments on the HST use. My comments are that the HST generates more heat by it's very operation and function. It also places a larger demand of work on the engine (efficiency wise).

The HST is smoother, as you point out, but that comes at a price for heat. That slow down isn't the engine magically throttling down, it's restriction of the flow of hydraulic fluid and that energy must go someplace, back to the sump and to heat.

The DT version is more efficient at getting power to the wheels, but it's not as versatile as the HST, which you point out. However, in non-PTO implement operations, it's just as functionally easy to use a DT as an HST for most operations. This is because you put the tractor at idle and use the throttle pedal almost like an HST. In PTO ops, both have to be set to PTO RPM's and you can add a little speed to the DT with the throttle pedal but not much. Taking it off requires putting in the clutch and changing gears or throttling down with the main throttle, so the HST is more versatile in that degree, as you pointed out.

Again, my point was addressing the heat of the system, not how it's used during mowing, though I can see how you could read it that way. The "inconsistent speed" comment is referring to the very easy of changing speed that you pointed out, but the cost heat wise of doing that which I explained above.

I like both systems and see the advantages and limitations of both. If I had the money, and if the dealer had an L3200HST laying around their lot (they didn't) I might have gotten that, it would've been a toss up. I certainly don't mind the DT, I'm used to geared tractors. The HST is a good choice, but I see them as equal systems, not competitors.

To the heat point, I'd have to actually measure the case temp of a DT versus an HST to see if the heat assumptions I am making really pan out. They should as generally, more efficient = less heat. One of those laws of thermodynamics thingies...

Good points, but we were talking engine overheating here, not transmission heat. I have no doubt that the HST transmission will run warmer than a manual, to a point. However, that is not something that is monitored on the Kubota standard L's, and it matters really little how warm the transmission is, it does not directly affect the engine operating temp, and the engine is what the temp gauge reads off of.

I guess if the HST were to get really HOT, then there could be some transference of heat from the transmission cooler to the air stream going past the radiator which may raise the engine temp a few degrees, but it would have to be very hot.

Careful though on the less heat = more efficient from a thermodynamics point. That is not always a set rule. A engine has to be at a certain temp to properly combust the fuel, and the warmer you run a engine, without self destructing it, the more efficiently it burns the fuel.

You other points are very well made. It is absolutely ridiculous that Kubota puts a gauge alone on these tractors, they need a light and buzzer, if not in addition the gauge, then in place of it. A gauge does nothing to draw the eye to it, where as a flashing light or buzzer demands immediate attention. A basic warning system would cost about a $100, not that much on a 20k tractor. Although I do realize these are the "basic" models and are built to a price point.

David

Kingcreek · Oct 24, 2014

yup. Had the same thing with my L3010. no damage and no problem after thorough clearing.

ShaunRH · Oct 24, 2014

dmanlyr said:
Good points, but we were talking engine overheating here, not transmission heat. I have no doubt that the HST transmission will run warmer than a manual, to a point. However, that is not something that is monitored on the Kubota standard L's, and it matters really little how warm the transmission is, it does not directly affect the engine operating temp, and the engine is what the temp gauge reads off of.

I guess if the HST were to get really HOT, then there could be some transference of heat from the transmission cooler to the air stream going past the radiator which may raise the engine temp a few degrees, but it would have to be very hot.

Careful though on the less heat = more efficient from a thermodynamics point. That is not always a set rule. A engine has to be at a certain temp to properly combust the fuel, and the warmer you run a engine, without self destructing it, the more efficiently it burns the fuel.

You other points are very well made. It is absolutely ridiculous that Kubota puts a gauge alone on these tractors, they need a light and buzzer, if not in addition the gauge, then in place of it. A gauge does nothing to draw the eye to it, where as a flashing light or buzzer demands immediate attention. A basic warning system would cost about a $100, not that much on a 20k tractor. Although I do realize these are the "basic" models and are built to a price point.

David

I am not specifically stating how much a warmer transmission would impact engine heat, I said the opposite, only that it might exacerbate the condition. It certainly would not run cooler than a geared drive given that the HST is commonly reported as running hot to the or too hot to touch when working hard. My DT tranny is warm to the touch but certainly not hot after working it. I do believe the HST's have oil coolers on them, I don't think my DT does, so if the engine radiator can get plugged, I'd keep an eye on the oil cooling radiator as well!

Speaking to Thermodynamics-
Since the two systems are so closely coupled and thermal conductivity happens between the engine and transmission of the vehicle, it should have an impact on engine temp. What that is would have to be determined, but like I said originally, if I had an HST, I would probably be even more vigilant on the cooling issue which was the point of the comment.

I'm not trying to ignite a holy war over transmission differences, only point out that the differences might have effects on an engine system that is cooling only to normal work loads, even when clean.

It is up to all of us to know the limitations of our units, no matter what we choose. I love my L3200, it's a nice tractor, and reading other threads, I knew it could suffer this issue, but I didn't expect how FAST the issue happened. So this thread is just a word of warning and lessons learned, not a primer on engine thermal design and thermo coupling of disparate mechanical systems.

Jim L. · Oct 24, 2014

This is the time of year that warm season grasses are producing fluff and getting ready to go dormant.

Mare's tail is bad about this and just the right height to hit the tractor front and load the radiator with junk. Not just the filter, but all the radiator fins.

Really do keep one eye on the temp gauge because it will heat up fast without air thru the radiator.

Stubbyie · Oct 27, 2014

We use on both our Kubotas a cheap $1 blue / white / pink fiberglass HVAC filter placed ahead of the screen that sits ahead of the radiator.

Gets a bit warm, stop, pull out filter, shake in wind, reinstall with same face oriented 'out', keep going.

In worst conditions, change at noon or end of day, otherwise as needed.

Inexpensive way to keep radiator clean when away from shop and power for vacuum or gentle air blow or hose wash.

HVAC techs in my area call these filters 'cat hair catchers' and use them as the primary in a stacked home air filtration system. Pretty much useless other than for catching gross air contaminants.

$1 at WM or Lowes; 50-cents each case of twenty at wholesaler.

Please post back your comments and experiences so we may all learn.

Bluegill · Oct 27, 2014

I mowed a fair bit the last two days, tall stuff with seeds & fluff. No over heating with the L3800. Actually most of the 150 hrs on this rig have been mowing and it has never over heated...

ShaunRH · Oct 27, 2014

Bluegill said:
I mowed a fair bit the last two days, tall stuff with seeds & fluff. No over heating with the L3800. Actually most of the 150 hrs on this rig have been mowing and it has never over heated...

I'm thinking it might be a very 'grass' dependent issue as well, so thanks for confirming it might not happen. The grass I was mowing seems to have been the culprit in the plugging action, at least the 'fluff' is what blows out of the radiator when I back blow it.

Bluegill · Oct 27, 2014

ShaunRH said:
I'm thinking it might be a very 'grass' dependent issue as well, so thanks for confirming it might not happen. The grass I was mowing seems to have been the culprit in the plugging action, at least the 'fluff' is what blows out of the radiator when I back blow it.

Probably is 'grass/conditions dependent'. The fields I mow, get mowed once a years, late in the summer, early fall. So grass, weeds and brush is tall. I do mow with the FEL off, if that makes a diff and at 1800-2000 rpm?

Diydave · Oct 28, 2014

My old Li85 that I bought used, had a pretty nifty solution, already in place. Someone draped nylon house screen, around the front nose of the sheet metal vents, where the air comes in. It was held in place with hog rings. You also have another solution, if you have the loader on it. Just lower the bucket, and angle it back slightly, and it will catch a lot of the loose flying stuff, and at the same time bend down the seedheads, so they won't slap on the sheetmetal (fiberglass, as the case may be), and get sucked in...

ShaunRH · Oct 29, 2014

Diydave- That's exactly how I mowed, using the FEL to lay down the grass first. There was a decent wind on both days so one direction would be clear of debris, the other I would be running in a cloud of my own dust... <cough><cough> I wore a dust mask for my own face and that was changed out about every 2 hours, so I'm not surprised the tractor had issues.

The nylon mesh part is supposed to be handled by the pre-filter screen, but I kinda like the idea of the cheap 'cat hair' remover filters between the screen and the radiator. I can buy those in bulk and just trash them or blow them out.

Overheating issue on L series verified

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