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Coolant oil mixed

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  • Coolant oil mixed

    So I was screwing around one weekend boost launching and ended up mixing my coolant and oil on my LMM. Its a built motor making about 1200HP. How do I go about testing to see if its a oil cooler issue or a failed water pump to block o-ring without tearing it down? I drained everything I got almost 5 gallons of mix and refilled the oil and let it idle, it idled fine and oil stayed clean. I added coolant one gallon at a time, pressure testing the cooling system after each gallon, and it would not hold pressure. Finally after the third gallon I checked my oil and found it had mixed again. I do not have a bypass yet but that is in the works as well. Any insight is greatly appreciated.

  • #2
    Originally posted by Alex
    So I was screwing around one weekend boost launching and ended up mixing my coolant and oil on my LMM. Its a built motor making about 1200HP. How do I go about testing to see if its a oil cooler issue or a failed water pump to block o-ring without tearing it down? I drained everything I got almost 5 gallons of mix and refilled the oil and let it idle, it idled fine and oil stayed clean. I added coolant one gallon at a time, pressure testing the cooling system after each gallon, and it would not hold pressure. Finally after the third gallon I checked my oil and found it had mixed again. I do not have a bypass yet but that is in the works as well. Any insight is greatly appreciated.

    I realized I posted this in the wrong category, not sure how to delete.
    Hi, my thoughts are, an oil cooler would most likely put oil in the cooling system as the oil psi is much higher than the cooling system pressure, the water pump to block or front cover o ring, seals the front cover, so this o ring would leak oil. It seems that from what you say it's a large leak. The water pump could be leak tested but I usually leak test them off the vehicle. You could also try capping off or use pinch off pliers to isolate the turbo coolant hoses and re test the cooling system. The worst case I have seen for a cooling system that has no external leaks, would not hold pressure and is mixing coolant and oil was a block that was cracked at the main journal webs.

    Sent from my SM-G975U using Tapatalk
    Last edited by DmaxStoreJake; 02-06-2020, 10:36 AM.
    2006 LBZ Daily Driver, Tractor, School Bus, Hot Rod Diesel , Crew Cab, Lifted, Hunting Rig , Cowboy Cadillac

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    • #3
      Originally posted by DMAXDR View Post
      Hi, my thoughts are, an oil cooler would most likely put oil in the cooling system as the oil psi is much higher than the cooling system pressure, the water pump to block or front cover o ring, seals the front cover, so this o ring would leak oil. It seems that from what you say it's a large leak. The water pump could be leak tested but I usually leak test them off the vehicle. You could also try capping off or use pinch off pliers to isolate the turbo coolant hoses and re test the cooling system. The worst case I have seen for a cooling system that has no external leaks, would not hold pressure and is mixing coolant and oil was a block that was cracked at the main journal webs.

      Sent from my SM-G975U using Tapatalk
      At this point I would rather have anything but a cracked block or head issues. Hopefully this weekend is nice enough to dig into this. I will report back with my finding. Thank you.

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      • #4
        So I finally got around to digging into this, found out the expansion plug behind the water pump blew out. Glad it wasn’t anything major.
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        • #5
          Originally posted by Alex View Post
          So I finally got around to digging into this, found out the expansion plug behind the water pump blew out. Glad it wasn’t anything major.
          Glad to hear you got it figured out and it wasn't anything major. Those kind of finds are always a sigh of relief!!
          Give us a call for all your Duramax needs! 877-469-3629

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