Block heater question

Discussion in '6.9L IH & 7.3L IDI Diesels' started by Ford420ci6point9, Oct 8, 2018.

  1. IDIBRONCO

    IDIBRONCO IDIBRONCO

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    I was told that this was the main cause of the external cracks in the early 6.9s. Or actually just the opposite. The hot water next to the cold cast iron would cause it to crack. The thicker casting in this area supposedly fixed this issue, but I still try to plug mine in warm/hot.
     
  2. Oledirtypearl86

    Oledirtypearl86 Full Access Member

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    It makes sense with hot cold cycles especially when the cast iron block is -30 and you start to heat it from the inside and I'm not sure but I don't think there is a thermal switch on the heater
     
  3. IDIBRONCO

    IDIBRONCO IDIBRONCO

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    I don't think so either. I think it's just on or off.
     
  4. Macrobb

    Macrobb Full Access Member

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    I currently have an '83-84 block with big cracks in that area that someone tried to repair(Got it for a parts/core along with other stuff).
    My friend has a '84 running 6.9 that cracked in that area and was repaired with JB weld. Surprisingly, it worked. Engine got pulled because it was only running on 7, but it still runs(Coolant was not leaking or mixing. Just something wasn't right).

    So, yes, a block heater can cause a crack in that area on 83-84 blocks. Pretty sure that does *not* apply to more modern IDIs, and even with a 'weak' block, plugging it in warm should be fine.
     
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  5. Oledirtypearl86

    Oledirtypearl86 Full Access Member

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    So I lived in the north east corner of Montana for a few and while there I worked for a farmer he had a 84 6.9 that had a block heater on both sides and a pan heater and he would plug it on at 6 am every morning when it was -35 and over -60 with wind chill and you could hear that the heaters were working and that block never seemed to seep or leak or crack on either side I wonder if the second block heater helped with consistent heat expansion across the block or maby he was just lucky
     
  6. tradergem

    tradergem Full Access Member

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    Last winter I bought a TC-3 ThermoCube that turns my block heater on when the temperature drops below 35* and turns it off above 45* and I bought a TC-2 ThermoCube that turns my battery blankets on below 20* and off above 30*.
    I with these ThermoCubes I don't have to worry about the wild temperature changes from above to below freezing during the fall and spring months and I don't have to mess with timers I just plug the truck in and let the ThermoCubes turn thing on and off.
     
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