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Thread: M1079 runs hot and shuts down

  1. #1
    Join Date
    Feb 2016
    pell city, al
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    Default M1079 runs hot and shuts down

    I must admit, I am not a Forum savvy kinda guy. I did not have much luck finding what I was looking for. I have a 2004 S & S M1079 (LMTV) that runs hot and shuts itself down. I replaced the coolant and when I did there were small pieces of red plastic in the coolant. About 6 pieces of all different sizes about 1/16" thick. Is there something internal (maybe a fan), that may have deteriorated? I have no idea what they were or where they came from. Any help/suggestions would be appreciated.

  2. #2
    Colonel M1078MAN's Avatar
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    Jul 2018
    SW Va, Roanoke County
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    Interesting. can you post a pic.

    How long have you had it, and the problem

    Has anyone worked on it plastic could be from a cap or plug..
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  3. #3
    4 Star General NDT's Avatar
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    Dec 2008
    Camp Wood/LC, TX
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    Any chunks of plastic floating around in the cooling system will for sure end up plugging the radiator tubes, leading to overheating. Flush everything and get the radiator rodded out.

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  5. #4
    Colonel Third From Texas's Avatar
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    Aug 2018
    Corpus Christi Texas
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    Only other option is to replace the rad, which will be silly-stupid-expensive because..."surplus junk from the military is meant to be sold for silly-stupid-expensive prices" LOL

  6. #5
    Join Date
    Aug 2018
    Port angeles wa
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    Chunks are bad, wonder what they came from? I assume you got them out of the bottom of the radiator when you drained it? since flow is from top to bottom they would have had to come thru the radiator to reach the bottom of the radiator. could be from a disintegrating coolant pipe coupling, failing hose, excess gasket sealant? at any rate, if that is what came out the bottom, what is stuck on the top of the radiator that was too large to flow thru the passages? I would drain enough coolant to remove the upper radiator hose and borrow/buy a small inspection camera to put into the upper port and inspect the passages. If you find a lot more red plastic, you might be able to backflush it out of the radiator. at any rate you can get a look at he passages and decide if the radiator needs internal work. The radiator of course also needs air flow to function so those passages(and the intercooler passages in front of the radiator) must also be clear. As the engine reaches op-temp the fan should be fully engaged and pulling a lot of air thru the radiator. No flow = no transfer = overheat

    Next question I have, is do you have pump output/coolant flow? There is a line that runs to the top rear port of the coolant expansion tank from the pressure side of the thermostat housing. If you remove the pressure cap on the tank and start the truck, you should be able to hear/see fluid being pumped/sprayed into the expansion tank(from back toward pressure cap). Your heater coolant input also comes from the same point on the thermostat housing, so the heater should have hot air as the engine warms. Coolant also runs down the bypass pipe(large stainless pipe in front of air compressor) to the transmission heat exchanger. It should also get warm as engine warms. No flow = no pump = overheat...

    If you have valid/unclogged radiator passages and airflow, and you have pump output/flow, I would suspect a stuck thermostat that is keeping the flow from reaching the radiator to be cooled. It is located in the housing on the top front of the engine where the upper radiator pipe connects to the engine... Quick test is to remove it, put it in a pan of water on the stove and warm it above 210F and watch if it opens...
    Last edited by Ronmar; 06-11-2019 at 11:34.

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