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I think I may have a tiny raw water leak in my heat exchanger

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    I think I may have a tiny raw water leak in my heat exchanger

    I have the half system on my 6.2 Horizon Bravo II set up. For the past few weeks my cooling system has been making coolant. My recovery tank stays full hot or cold and will leak about 16 ounces of fluid into a water bottle I strategically placed at the end of the overflow hose from the recovery tank on the bilge floor. The engine runs fine, oil looks fantastic, temp stays around 167 -170 at cruise and the heat exchanger fluid level is always full as well. Regardless of filling up the water bottle with 16 ounces each weekend and removing that from my boat, my fluid levels remain full. All I can imagine is that I have a pin hole leak allowing raw water to escape to the fresh water side of the system. Any thoughts?
    Johnson Point, Olympia, WA
    1989 2855
    Horizon 6.2 and Bravo II

    #2
    my thought is that it is possible to have a pin hole leak, but due to the pressures that are created in the closed portion of the cooling system when running, it should push coolant OUT of the system into the open side, so that you should see a lowering of the coolant rather than a filling of it.... UNLESS the system is sucking seawater back in thru the pin hole as the system cools down... which is very likely what is going on there.

    if you are in salt water, you should be able to taste the coolant/water for salt after a couple times of draining the system, as the concentration should be high enough to give a good indication if what you suspect is true...... yes, its poison if you drink it, but you can taste it without harm to yourself.



    NU LIBERTE'
    Salem, OR

    1989 Bayliner 2556 Convertible
    5.7 OMC Cobra - 15.5x11 prop
    N2K equipped throughout..
    2014 Ram 3500 crew cab, 6.7 Cummins
    2007 M-3705 SLC weekend warrior, 5th wheel
    '04 Polaris Sportsman 700 -- '05 Polaris Sportsman 500 HO
    Heavy Equipment Repair and Specialty Welding

    Comment


      #3
      I also think you’d definitely loose coolant from a compromised HE. Has the coolant recently been drained and refilled (overfilled)?
      Just a guess here but your fresh potable water system runs at a substantially higher pressure than the closed side of the engine. Maybe your water heater exchanger has failed and is allowing some potable water to be pushed into the closed cooled side???
      Dave
      Edmonds, WA
      "THE FIX"
      '93 2556 5.7 Bravo II 2.0:1 18 1/4x19 P
      (.030 over-Vortec top end-part closed cooled)
      The rebuild of my 2556 https://www.baylinerownersclub.org/f...76?view=thread
      Misc. projects thread
      https://www.baylinerownersclub.org/f...56-gctid789773

      Comment


      • watchthis
        watchthis commented
        Editing a comment
        I hadn't considered that Dave. The coolant was not drained this year and none has been added. Hard to beat a boating mystery.

      #4
      Go to your favorite auto parts store and rent a radiator pressure test kit. The kit has a pump with a stepped rubber plug and a gauge. You tighten the rubber plug in place of the radiator cap, pump up the pressure then watch to see if the pressure holds. You could, maybe, remove the end caps from the he and possibly see which tube the leak is in. The rule of thumb, when things were repaired instead of replaced, was you could plug up to four of the tubes before replacing the he. It doesn’t take to plug off a tube. A little cleaning then fill the ends with marine tex, let it cure and reassemble.
      P/C Pete
      Edmonds Yacht Club (Commodore 1993)
      1988 3818 "GLAUBEN”
      Hino EH700 175 Onan MDKD Genset
      1980 Encounter Sunbridge "Misty Blue" (Sold)
      MMSI 367770440
      1972 Chevrolet Nova Frame off Resto-mod in the garage
      Boating on the Salish Sea since 1948

      Comment


      • builderdude
        builderdude commented
        Editing a comment
        Pete, he’s not loosing though he’s gaining EG coolant😳

      #5
      A pressure test would identify the existence of a leak. Be sure the domestic water pump is turned off. Like the he, you could disconnect the domestic water from the tank, drain the tank then look for coolant should the pressure go down. Dude, the gaining would indicate the possibility of the source being in the hwt as you say. If the domestic water pump is cycling there’s a good indication of a leak in the system. It’s also probable that the domestic water pump is turned on before the engine, creates more pressure than the cooling system and is turned off after the engine is shut down.
      P/C Pete
      Edmonds Yacht Club (Commodore 1993)
      1988 3818 "GLAUBEN”
      Hino EH700 175 Onan MDKD Genset
      1980 Encounter Sunbridge "Misty Blue" (Sold)
      MMSI 367770440
      1972 Chevrolet Nova Frame off Resto-mod in the garage
      Boating on the Salish Sea since 1948

      Comment


      • watchthis
        watchthis commented
        Editing a comment
        Thank you Pete. Weirdly enough, the domestic water pump has started to cycle for a few seconds here and there without a faucet being in use. I will try to get through August and dig in to the matter when the rain comes.

      #6
      No problem. Be careful that you don’t have coolant water having more pressure than the domestic system. You really don’t want coolant in your domestic system. You might consider disconnecting and either plugging the ends or connecting them together eliminating any possible coolant transfer. You could also rig something up to capture any domestic water leaking from the coolant pipes in the water heater.
      P/C Pete
      Edmonds Yacht Club (Commodore 1993)
      1988 3818 "GLAUBEN”
      Hino EH700 175 Onan MDKD Genset
      1980 Encounter Sunbridge "Misty Blue" (Sold)
      MMSI 367770440
      1972 Chevrolet Nova Frame off Resto-mod in the garage
      Boating on the Salish Sea since 1948

      Comment


        #7
        Id pressure test the water heaters heat exchanger up to at least the operating pressure of the potable water system, 55 psi maybe a bit more. You could also bypass the EG loop to the water heater and see if you quit “making coolant”.
        Dave
        Edmonds, WA
        "THE FIX"
        '93 2556 5.7 Bravo II 2.0:1 18 1/4x19 P
        (.030 over-Vortec top end-part closed cooled)
        The rebuild of my 2556 https://www.baylinerownersclub.org/f...76?view=thread
        Misc. projects thread
        https://www.baylinerownersclub.org/f...56-gctid789773

        Comment


          #8
          ................
          Originally posted by watchthis View Post
          I have the half system on my 6.2 Horizon Bravo II set up. For the past few weeks my cooling system has been making coolant. My recovery tank stays full hot or cold
          Is this recovery reservoir at close to the same elevation as the Heat Exchanger? These work best when they are close to the same elevation.
          Do you have the correct pressure cap for a recovery system?
          The correct cap will have two areas of seating..... one for pressure release, and one that allows coolant to be drawn back in from the recovery reservoir during engine cool-down!



          and will leak about 16 ounces of fluid into a water bottle I strategically placed at the end of the overflow hose from the recovery tank on the bilge floor.
          Are you saying that the recovery reservoir itself suffers from an over-flow, and that you are capturing this over-flow to the tune of 16 ounces?
          How often are you seeing 16 oz?


          The engine runs fine, oil looks fantastic, temp stays around 167 -170 at cruise and the heat exchanger fluid level is always full as well. Regardless of filling up the water bottle with 16 ounces each weekend and removing that from my boat, my fluid levels remain full.
          It may be remaining full, but it is now no doubt diluted!
          Make sure that you keep the correct 50%/50% mix of ethylene glycol and distilled H2O in the system.
          A weak mix of coolant will not do as well at removing heat from the engine, not to mention the lack of lubrication at the coolant circulating pump seal.


          All I can imagine is that I have a pin hole leak allowing raw water to escape to the fresh water side of the system. Any thoughts?
          As per Centerline (post #2), the coolant pressure will exceed the pressure on the seawater side of the system.
          In other words, it is extremely unlikely that seawater could be entering the Heat Exchanger..... unless, it is entering upon the "cool-down" cycle during the time that the system would otherwise recover coolant from the recovery reservoir.


          As per Dave (post #3), the water heater's "heat exchanger" could also be the culprit.
          I would use Dave's suggestion (post #7) and take the Water Heater's engine coolant out of the loop for testing.
          Simply disconnect the Water Heater's supply and return hoses, and join then together.

          As another suggestion if you boat in ocean water........., see if you can find test strips that will detect salt within ethylene glycol.
          If you detect salt, then you'll have a more defined direction to head towards.
          If you do not detect salt, then it would more likely point towards the Water Heater.

          .
          Rick E. Gresham, Oregon
          2850 Bounty Sedan Flybridge model
          Twin 280 HP 5.7's w/ Closed Cooling
          Volvo Penta DuoProp Drives
          Kohler 4 CZ Gen Set

          Comment


          • watchthis
            watchthis commented
            Editing a comment
            Rick:

            The recovery tank is at the same height and I have had the same cap for 4 years since I purchased this boat without this recent mystery. The recovery tank overflows through the tube that extends from it to the bilge floor and that is what I capture in a separate bottle, put a cap on it and dispose of it in our marina's hazardous waste collection box. A week ago I captured roughly 16 ounces after about 90 minutes at cruise, roughly 3600 rpms at 21 knots.

          #9
          To conclude this story, yes my hot water heater was shot, but so was my heat exchanger on the engine half system. My newly made coolant was in fact salty to the taste. Flushed her out, replaced the heat exchanger with Mercruiser OEM (FedEx overnight from Wisconsin - ouch!!!) and dropped a new Kuuma water heater in. No more coolant manufacturing. I appreciate everyone who assisted me. Ya'll are great. Enjoy Labor Day weekend safely.
          Johnson Point, Olympia, WA
          1989 2855
          Horizon 6.2 and Bravo II

          Comment


            #10
            Glad you’ve resolved your issue(s).
            Happy boating😁
            Dave
            Edmonds, WA
            "THE FIX"
            '93 2556 5.7 Bravo II 2.0:1 18 1/4x19 P
            (.030 over-Vortec top end-part closed cooled)
            The rebuild of my 2556 https://www.baylinerownersclub.org/f...76?view=thread
            Misc. projects thread
            https://www.baylinerownersclub.org/f...56-gctid789773

            Comment


              #11
              Same here...... and happy boating!
              Rick E. Gresham, Oregon
              2850 Bounty Sedan Flybridge model
              Twin 280 HP 5.7's w/ Closed Cooling
              Volvo Penta DuoProp Drives
              Kohler 4 CZ Gen Set

              Comment

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