Chronic Kioti DK40 SE Overheating - Seeking Advice on Removing Thermostat

[Rhino35]

I have a nearly identical setup with my Branson. My engine hp is 37, but my pto hp is 32. Almost an exact duplicate of what you're running. Mine is also "heavy" (4200 lbs bare chassis) and my rear tires are also filled with Rimguard. All that to say, I am also running a 6' brush hog, and our summers regularly get to 90-95 degrees with humidity. The only time I have issues with getting hot is once my radiator and coolers get plugged with chaff from mowing. And I'm running a cabbed tractor with a/c. And when it's hot out, you better believe I have that a/c cranking.

Once I blow the chaff out of my radiator and coolers, the temp gauge drops right back to the normal range again. Sometimes I can go for hours, sometimes all day, sometimes I have to stop every "lap" I take on the field. It really depends on the field and how much chaff I'm kicking up on that job. Last job I did the field was very soggy wet so there was no chaff at all to contend with. I ran for 6 hours straight (well I did stop to replace one broken shear pin) with no overheating issues at all. Meant to add, this was a field with average weed/grass height of top of the hood, and a few areas where the weeds were 6 feet tall.

Point of all this ramble? I don't think you need to second guess your tractor choice, either size or hp rating. There's something else at play here.

Thanks for the useful identical configuration comparison. I have hills and when this overheating process begins I can watch the temperature gauge start going up going uphill and go down going down. The chaff building up sounds so similar. I do hop down and blow it off with a leaf blower and start the cool down, then heat build-up process - over and over and sometimes it is one lap. This is useful to know - and I'll try cutting open the thermostat to eliminate it not opening. That would serve as a "restrictor".

 

[Slowpoke Slim]

Thanks for the useful identical configuration comparison. I have hills and when this overheating process begins I can watch the temperature gauge start going up going uphill and go down going down. The chaff building up sounds so similar. I do hop down and blow it off with a leaf blower and start the cool down, then heat build-up process - over and over and sometimes it is one lap. This is useful to know - and I'll try cutting open the thermostat to eliminate it not opening. That would serve as a "restrictor".

I only ever blow out the radiator from the engine side outwards to the front. Never blow from the front side in. If you do that you are blowing chaff deeper into the rows of fins. Blowing it only from the back side forwards forces out through the path of least resistance and you're more likely to get most or all of it out.

I tried to use a leaf blower once and just couldn't get it in the tight spaces and between the fan, fan shroud and get it close enough to the back of the radiator to do any good. Wasn't getting enough air actually directed through the rows of fins. I use the air wand out of the "Radiator Genie" set, which easily fits and reaches across the entire back side of the radiator (coming in from both right and left sides).

I also set my air pressure out of my compressor to 40-ish psi. Be very careful not to hit that aluminum finned radiator with too much air pressure. Those paper thin fins are extremely easy to fold over (like when hitting them with 100-120 psi air, or scraping the wand tip across the fins).

 

[Slowpoke Slim]

This is a great suggestion!

Do yourself a favor and pressure test your radiator cap and coolant system before diddling around with taking the thermostat out (again).

I find it much less likely that you ran into 2 separate "bad" thermostats in a row. And frankly, it just doesn't match the symptoms you are describing.

 

[ericm979]

It it used to work properly under the same conditions and you have replaced the thermostat, the thermostat is not the problem. Maybe removing it or cutting it down can make up for the real problem, but it won't fix it. I kind of doubt that a fully open thermostat is that much of a bottleneck so I don't think removing it or cutting it down will change much.

With the engine off can you turn the fan by hand? If so the belt's not tight enough. Or it's old and hard. If it's slipping both the fan and the water pump will turn slower than they're supposed to.

 

[Alan46]

It it used to work properly under the same conditions and you have replaced the thermostat, the thermostat is not the problem. Maybe removing it or cutting it down can make up for the real problem, but it won't fix it. I kind of doubt that a fully open thermostat is that much of a bottleneck so I don't think removing it or cutting it down will change much.

With the engine off can you turn the fan by hand? If so the belt's not tight enough. Or it's old and hard. If it's slipping both the fan and the water pump will turn slower than they're supposed to.

Very true!

 

[RandyT]

Could there be a chance that the water pump impellor is slipping on the water pump shaft.

 

[EddieWalker]

Can you see through the fins of your radiator? It has to be one of two things, either your radiator is dirty, or your fan/belt/water pump isn't working like it should. I think the thermostat is good and not worth the time to mess with.

If it was me, I would get the hose out and soak the radiator for half an hour. Just keep the hose on it until you get totally clear water coming off of the radiator. This would be cheap, fast and easy.

Then hit it with the air to see if anything comes out of the fins. Get a wand that goes onto your air hose. Mine has two feet of metal with a 90 degree bend at the end so I can get into the corners, and in front of the fan. I blow from the engine side of the radiator. I do this until I don't see any dust at all coming out. Sometimes it's just a couple minutes, sometimes it's ten minutes. Every time, there's dirt in there!!!

 

[DonRybak]

Rhino35, any updates? I agree with others that it's most likely an air flow issue. I too use the Radiator Genie wands because they make it easy to get between to radiator and engine to blow from back to front. Not sure about your tractor but my RK37 has a screen too that if you don't pay attention you could easily miss so that you are just blowing the trash onto the screen so that it gets sucked back into the radiator. Also, the chuck that came on my wand wasn't the standard chuck so the air leaked around it. There's a youtube video out there explaining it. I bought an adapter off Amazon for something like $7 that took care of that issue. There's also a couple good videos out there on the Radiator Genie.

 

[Rhino35]

It it used to work properly under the same conditions and you have replaced the thermostat, the thermostat is not the problem. Maybe removing it or cutting it down can make up for the real problem, but it won't fix it. I kind of doubt that a fully open thermostat is that much of a bottleneck so I don't think removing it or cutting it down will change much.

With the engine off can you turn the fan by hand? If so the belt's not tight enough. Or it's old and hard. If it's slipping both the fan and the water pump will turn slower than they're supposed to.

A few days ago, ambient temperature about 80F, I wanted to see if the coolant was circulating since a poster said to check that. So I started the engine and slowly drove out of my garage in hydro low gear and 1300 RPM. Engine had been running only 3-4 minutes when I opened the radiator cap. Coolant splashed out - like it was overfilled. I was surprised - I thought I'd just see the coolant below the cap stationary (not under pressure like it was), and then as the engine warmed up and the thermostat opened begin to flow. The overflow bottle I've kept at about half - there is a fill line and its always been close to that when cold. It does go up and down.

I blew out the radiator with compressed air - higher PSI than 40. Probably 100 psi and then as I held the hand air valve open it dropped to 50-80 psi. Lots of fine particle dust, brownish, like before when I've done this. I blew it out front to back at first, then back to front - a long time moving all around the obstacles to get it to where no appreciable dust blew out. There is an oil cooler radiator low in front of the engine coolant radiator and that seemed to have a lot of dust. As an observation my tractor's engine coolant radiator has a lot of stuff in front of it. The battery, the oil cooler, the air filter housing, and a big air pipe from the air filter up and over the radiator top to the engine.

I can move the fan by hand about 1/8th revolution, but it takes almost all my strength. Is that too loose? Every time I've looked at the running engine at idle RPM that fan is spinning. I haven't looked at it with engine RPM at 2,500 RPM - I'd need someone at the controls before I'd do that. I moved it so I could blow out the radiator back to front where the fan blades had blocked the radiator. That allowed more dust to blow out, which was good to see. I don't think the drive belt is too loose, but possibly that is an underlying problem.

I then worked the tractor by bush hogging medium high stuff on fairly level land in two wheel drive, then engaged four wheel drive and went up and down the hillside bush hogging. Temp gauge stayed put.

I used the thermal sensing gun with the engine warmed up and stable and the gauge reading normal. All temps read plus or minus about 2 degree C as I moved the gun around. Temperature was 67C at the radiator cap, 67 degrees at the very front of the engine, and about 90C near the back of the engine. It was 67C at the rear differential area too. I'll carry the gun with me and if it starts heating up I'll check these areas again. Any tips here?

Thanks!

Finface

 

[EddieWalker]

I would hit it with the hose and really soak it good, then blow it out with air.

When you move the fan, is it sliding along the belt, or are you moving the fan and the belt at the same time? A loose belt can cause overheating.