Mowing Kubota L3800 overheating only when mowing

[rvenettozzi]

We bought a used (239 hrs) Kubota L3800 HST last year from the local Kubota dealer. The tractor runs well as long as we are not using the mower (King Kutter 60"). Within a 30 minute space of time mowing one of the horse pastures, the tractor will overheat. We've changed the thermostat; nothing changed. (The parts guy at Kubota suggested we let the needle run into the red to see what happens, but we don't want to buy a new engine.) When the needle moves from the white to the red, I turn the tractor off--and can hear the radiator water boiling. Does anyone have any suggestions?

 

[Citydude]

Have you checked the radiator for chaff buildup?

 

[rvenettozzi]

We have checked the radiator and the screen--both are clean.

 

[tractorshopper]

I never had an issue with my L3800 even bush hogging 8 hrs at a time (60" Land Pride). Only time ever came close to getting above middle temp, I cleaned the screen and it cooled right back down immediately.

Is the fan working?

 

[ultrarunner]

I've investigated problems where the radiator looked clean but blocked light from going through.

If the radiator is full and clean, thermostat is good, fan and belts good there are only two things come to mind...

Head gasket or an obstruction in the cooling system.

We have an L3800 and so far it has really been problem free... use it mostly for loader, bush hog and some backhoe work...

I agree, I would not let it run in the red just to see what might happen.

Radiators can be flow tested... there are ways to check head gaskets.

Sure sounds like a bad thermostat...

At one time I would check them in a pot of water on the stove before replacing... had a lab thermometer that would go to 300F

 

[Fallon]

I have had a fair amount of issues with my L32pp running hot while mowing. Cleaning the screen almost always fixes it. It didn't last time because I've been cleaning it while running. Now a lot of crap is on the radiator. Need to get around to blowing it out.

 

[rvenettozzi]

Hi, there! I'm the one eating crow . . . if enough people suggest the same thing, then it's time to recheck. All of you were right. We pulled out the screen, craned our necks, and voila--chaff. A good cleaning with the air hose solved the problem. We just mowed for 30 minutes with no overheating issues. Thank you to all who replied. You're the best.

 

[ultrarunner]

I'm sure glad you paid attention and didn't run her in the red... I guess it's good for the parts department to drum up sales.

I've used engine degreaser or simply Dawn to rinse radiator fins... important to use very low pressure like the end of a garden hose on a cold motor and no spray nozzle...

It doesn't take much to impede cooling... especially in the environments tractors operate.

 

[Grandad4]

Would have to agree the most likely cause is a build-up of crud on the vanes of the radiator. The screen catches the bigger debris but you wouldn't believe how much fine dirt gets through and plugs up the radiator. You may not "see" it just by looking, but gently rinsing the radiator with water (no pressure washer or full blasts from the hose!), will flush enough dirt to make the water turn brown. A combination of rinsing and air seems to work the best for me. If a lot of those 200+ hours have been spent mowing and it's not been cleaned, it's sure to need it badly. The shrouds, fans, etc. make it a pain to clean well but I do it a couple of times each mowing season and the temp gauges never go above about 1/3 of the scale.

Don't know what kind of doofus would tell you to let it go into the red zone just to see what happens. Have the genius sign an agreement it's on him to pay for any resulting damage. Sheesh.

 

[Citydude]

Hi, there! I'm the one eating crow . . . if enough people suggest the same thing, then it's time to recheck. All of you were right. We pulled out the screen, craned our necks, and voila--chaff. A good cleaning with the air hose solved the problem. We just mowed for 30 minutes with no overheating issues. Thank you to all who replied. You're the best.

That's what we're here for. Glad you found the problem. Happy tractoring.