718D Grasshopper Overheating

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

  1. Mowingman

    Mowingman LawnSite Platinum Member
    from Texas
    Posts: 4,663

    As mentioned above, check the fan for proper operation. Next step would probably be checking the thermostat. Hard to believe the water pump would go out at such low hours, but, I suppose old age could affect the seals on that pump.
     
  2. JCLawn and more

    JCLawn and more LawnSite Fanatic
    from MI
    Posts: 5,206

    I have a 93 721d. Its always ran hot. Lowest it runs is 190 while mowing. It wil run 220+ when its 80+ out. it will climb to 260 quick if the radiator is dirty. just try to keep the radiator screen clean. We have a fixed fan with a belt so nothing can go wrong. I've often thought about adding a aux radiator on the side of the mower.
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  3. viper8524

    viper8524 LawnSite Member
    Posts: 45

    Good check with a laser thermometer is to see the temp differential between the upper and lower coolant hoses, lower should be 15-25 degrees cooler if the coolant is moving properly and the radiator and fan are pulling air thru it properly.

    Also could hook up a pressure tester where the rad cap goes and check the system for holding pressure. This is a good test for head, block and or head gasket cracks, leaks,etc.

    Also does the engine rpms bog down under load and or slow to recover from climbing a hill or cutting heavy/tall grass. If so sometimes, the kubota injection pumps have issues where they dont advance the fuel curve under load and this causes the engine to run lean and bog down creating an overheat condition.
     
  4. JCLawn and more

    JCLawn and more LawnSite Fanatic
    from MI
    Posts: 5,206

    Lean on a diesel makes it run cool. I do know a woods mower that is having that issue though. Mine I can see black smoke come out under load so its getting plenty of fuel.
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  5. jarnod1993

    jarnod1993 LawnSite Member
    Posts: 7

    I got a new thermostat for the mower and installed it. It seemed to be doing ok until it blew the lower radiator hose. I've ordered a new hose and as soon as it comes in I'll try it again. The fan is working properly it's moving a lot of air across the radiator. I'll check the hose temperatures when I get the new hose. The engine does throw out some black smoke when it is under a load but is pretty quick to pick up the rpm after being bogged down. For a 1990 model grasshopper it still has a lot of power.
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  6. jarnod1993

    jarnod1993 LawnSite Member
    Posts: 7

    The new hose finally came in and I out it on this afternoon and tried the mower again and it still overheated. Does anyone have anything else to try?
     
  7. JCLawn and more

    JCLawn and more LawnSite Fanatic
    from MI
    Posts: 5,206


    Got confused on the thread. My GH has always overheated. I think the radiator is just to small.
     
  8. JCLawn and more

    JCLawn and more LawnSite Fanatic
    from MI
    Posts: 5,206

    I do remember because of how big I am my seat actually hits the screen and the girl who worked for me last summer the seat would be 2-3 inches away from it and she never had overheating issues.
     

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