Zd21 overheating.

[met828]

Kubota zd21 diesel zero turn keeps overheating. Only when the blades are engaged. I found and replaced a cracked head, mower will drive around fine without the blades on. Took mowing deck down and found spindle assembly flat worn out. So I replaced the bearings. Ran longer this time with the blades on but still boiled over. I moved the pto shaft that runs the the blade by hand, it seemed a little tight but engine was off so I assumed it probably has a pto brake that was applied. Looking for what to check now all spindles spin free now. Oh also to note my yard was mowed before I tried to mow with this kubota. The engine acts like it has a heavy load on it in the thicker parts of my yard, but grass was already cut to about an inch or two in length the day before.

 

[Captain13]

Have you cleaned the radiator screen behind the seat? Blown through the radiator fins? My ZD21 actually runs cool unless that screen is dirty. How about the thermostat?

Any bubbles in the coolant indicating the head gasket didn’t seal?

 

[met828]

Have you cleaned the radiator screen behind the seat? Blown through the radiator fins? My ZD21 actually runs cool unless that screen is dirty. How about the thermostat?

Any bubbles in the coolant indicating the head gasket didn’t seal?

I removed radiator sprayed purple power on the fins then flushed it, then put hose inside of radiator for a good flush there as well. Thermostat opens in boiling water. I did run the machine with cap off radiator and didn’t see the bubbles like I did before.

 

[Captain13]

Check your fan belt, your radiator cap may be bad, clean the air filter. Don’t laugh at the air filter check. I’ve read where a severely clogged air filter has caused Kubotas to overheat. Oil level ok, oil weight ok, fan shroud in place with no cracks.