Kubota Diesel Zero Turn Overheating - HELP

RTR · Jul 26, 2018

We have this Kunitz diesel mower model ZD-21 that will overheat after approximately 15 minutes of use. I arrived to the site to inspect it and upon arrival it appeared to be empty of coolant in radiator and overflow bottle. We didn’t have coolant on site so I filled it with water (a little too much). They ran the machine after we left and said it overheated again. I found it in the shed this morning and it appeared empty in radiator and overflow tank again!!! I filled with water and told supervisor to run it while I went to bathroom. When I came out She said it shut down on her, was blowing black smoke and was overheated. I went immediately to look for leaks and only found it blew water out the overflow tube but no leaks anywhere else. Was definitely overheated and overflow bottle water level was higher and it was burping. Oil was also leaking out of the filler on the top of valve cover. Oil level in engine is perfect.

At a loss. What’s wrong!?!? Thermostat? Stopped up radiator? Head gasket?

ohiojim · Jul 26, 2018

sounds like a head gasket. if you're lucky, cracked head also comes to mind

Janicholson · Jul 26, 2018

That would be my guess as well. Pressure/leakdown check the cooling system. With a leak that bad it will show up immediately. Pull the spark plugs and after the check, crank it for a second and coolant will blow out the affected cylinder. Jim

RTR · Jul 26, 2018

(quoted from post at 19:46:07 07/26/18) sounds like a head gasket. if you're lucky, cracked head also comes to mind

Sorry for the typo.....it's a Kubota (not that it isn't obvious with the picture).

You really think it would be a head gasket and possibly cracked head? I tried watching for bubbles in the radiator but with such A small filler neck, it was hard to see.

RTR · Jul 26, 2018

(quoted from post at 20:00:04 07/26/18) That would be my guess as well. Pressure/leakdown check the cooling system. With a leak that bad it will show up immediately. Pull the spark plugs and after the check, crank it for a second and coolant will blow out the affected cylinder. Jim

This mower is a 3 cylinder diesel Jim.

RM-MN · Jul 26, 2018

fill the radiator clear to the neck, then with the fuel shut off so the engine won't start, crank it and watch for bubbles/blowover. No bubbles/blowover says thermostat stuck. Bubbles says pull the head and look for blown head gasket or cracked head.

mozark · Jul 26, 2018

I would check the obvious first, fan belt, plugged radiator fins, and then fill with appropriate coolant(not just water). That's pretty quick for one to overheat, but not if its already hot though. Could be bad head gasket, or cracked head, may not have been the original problem, but now that it has overheated several times its a definite possibility. Good luck. I have a Kubota BX tractor and it runs near the red when mowing especially when it is hot out, if I remove all the tupperware it runs much cooler. Radiator fins get plugged easily too.

RTR · Jul 26, 2018

(quoted from post at 20:33:53 07/26/18) fill the radiator clear to the neck, then with the fuel shut off so the engine won't start, crank it and watch for bubbles/blowover. No bubbles/blowover says thermostat stuck. Bubbles says pull the head and look for blown head gasket or cracked head.

Where is the coolant escaping to so quickly??

old popper · Jul 26, 2018

Didn't know diesels had spark plugs?????

BarnyardEngineering · Jul 26, 2018

(quoted from post at 09:30:37 07/26/18)Where is the coolant escaping to so quickly??

My guess is its blowing right out the overflow under the operator's nose, but since they're just hired help, they don't pay any attention. They just run it until it stops moving, then call you to come and fix it.

Janicholson · Jul 26, 2018

Yeah, once into the story I forgot the title. Injector then, Jim

MarkB_MI · Jul 26, 2018

Head gasket is #1 suspect. And after being overheated repeatedly it might have a cracked head.

Get a cooling system pressure tester and follow the instructions to test for a blown head gasket.

jm. · Jul 26, 2018

More than likely your operator over heated it by not cleaning the radiator screen. Now you have a CRACKED HEAD. You water (coolant) is going out the exhaust and you are not seeing it. Caution stop leak will NOT fix the cracked. And if you tear it down now have a professional check the head because the crack is easy to miss. And most tomes we go on and stick a set of rings in there because the heat has worked on the rings. Dealer bill will be $1700 to $2200. I sell a lot of running take out engines.

RTR · Jul 26, 2018

(quoted from post at 02:40:19 07/27/18) More than likely your operator over heated it by not cleaning the radiator screen. Now you have a CRACKED HEAD. You water (coolant) is going out the exhaust and you are not seeing it. Caution stop leak will NOT fix the cracked. And if you tear it down now have a professional check the head because the crack is easy to miss. And most tomes we go on and stick a set of rings in there because the heat has worked on the rings. Dealer bill will be $1700 to $2200. I sell a lot of running take out engines.

Yeah I should have mentioned that oil was coming out the filler cap on the valve cover. It was also hard to start this morning when I went to get it out of the shed. Turned over for about 20 seconds before it started and it took me cranking it over whee it was "starting" to get it to run.

WGM · Jul 26, 2018

Where is the tupperware at?

showcrop · Jul 26, 2018

Let me say first that jm. is the resident Kubota expert, so pay close attention to what he is telling you. Let me add that when you filled it this AM you didn't. You filled the radiator but the water jacket was still pretty much dry, which is why it overheated and started blowing oil in the time that it took you to take a whizz.

RTR · Jul 27, 2018

(quoted from post at 03:26:14 07/27/18) Where is the tupperware at?

Tupperware??

RTR · Jul 27, 2018

(quoted from post at 03:28:51 07/27/18)
Let me say first that jm. is the resident Kubota expert, so pay close attention to what he is telling you. Let me add that when you filled it this AM you didn't. You filled the radiator but the water jacket was still pretty much dry, which is why it overheated and started blowing oil in the time that it took you to take a whizz.

10-4

Blackhole49 · Jul 27, 2018

X2 on jm. I'm betting on a cracked head.

Blackhole49 · Jul 27, 2018

I too would like to know what you are referring to as "tupperware".

showcrop · Jul 27, 2018

(quoted from post at 06:55:12 07/27/18) I too would like to know what you are referring to as "tupperware".

Perhaps plastic shields, covers, etc. Plasticware?

mozark · Jul 27, 2018

Tupperware is what we motorcycle riders call the plastic shroud around the engine area. Since the radiator and fan are just forward of the steering column, the plastic shroud around the engine area blocks a lot of air flow. The fan is further handicapped because the fan blows forward against the direction of travel. The temperature gauge will run just below the red when outside temp is 85+ degrees and you are mowing hard. Removing the shroud causes the needle on the unmarked temperature gauge to drop about 1/4" (which is about 1/8" above normal operating temp).

Kubota Diesel Zero Turn Overheating - HELP

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