718D Grasshopper Overheating

Discussion in 'Mechanic and Repair' started by jarnod1993, Apr 23, 2014.

  1. jarnod1993

    jarnod1993 LawnSite Member
    Messages: 7

    I have a 718D grasshopper. It has been overheating on me. It started overheating last season and I ended up replacing the radiator but was mowing with it again this season and is still over heating. It is okay at idle but when you are mowing with it the mower will overheat. Then if you turn the the deck off it will cool down and you can go back to mowing until it overheats again. Any information on what could be causing the problem would be greatly appreciated.
  2. herler

    herler LawnSite Fanatic
    Messages: 5,139

    Faulty / sticking thermostat, still functioning but not correctly, I would simply replace it, eliminate this as a possibility.
    Low on antifreeze, this and the thermostat would be my first two options.
    Failing water pump.

    How dirty is the engine?
  3. jarnod1993

    jarnod1993 LawnSite Member
    Messages: 7

    The coolant level is good in the mower. I haven't replaced thermostat but will try and do so to see if the problem persists. Also the engine is very clean I just took all the covers off and cleaned out any old grass and degreased it. Thanks
  4. viper8524

    viper8524 LawnSite Member
    Messages: 45

    engine ever low on coolant or use it? Ever see any air bubbling in the expansion tank maybe indicating a bad head gasket or cracked head,etc.

    also ever hear any belt squeals from the water pump/alternator area. Those alternator and water pump pulleys are bad for wearing grooves in them and then the belt slips.
  5. jarnod1993

    jarnod1993 LawnSite Member
    Messages: 7

    It's never been low on coolant and I check it every time I use it. I've also never heard any belts squealing I've spun both the alternator and water pump and both spin smoothly. I'm not sure about the bubbling but I've never seen any water in the oil or oil floating in the water.
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  6. bob

    bob LawnSite Platinum Member
    from DE
    Messages: 4,260

    What about an air bubble in the system when the radiator was replaced? The water pump can't pump air.
  7. windflower

    windflower LawnSite Bronze Member
    Messages: 1,111

    My walker diesel had similar symptoms. Ended up being a relay for the radiator fan not working right. Fan only worked some of the time. Mower would idle fine but over heat while mowing.
  8. jarnod1993

    jarnod1993 LawnSite Member
    Messages: 7

    That's a good thought. I hadn't thought about air in the system. Also is it common for the water pump to go out on kubota engines?
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  9. Mowingman

    Mowingman LawnSite Platinum Member
    from Texas
    Messages: 4,721

    Isn't that a pretty old machine? I don't remember the 18hp Kubota diesel being offered for a long time.
    How many hours, and what year model is it?
  10. jarnod1993

    jarnod1993 LawnSite Member
    Messages: 7

    Yes it's pretty old. I belive it is a 90 model and the hours are around 1600
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