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    #16
    Originally posted by DIYglenn View Post
    I did open it a bit too early once, and got a mean hiss.
    Could it be that the cap isn't opening up correctly when hot?
    There's some rust on the cap, and the black paint is peeling, should it be replaced?
    depending on the system, when the system is hot, the rating on the pressure cap is the pressure you can expect to be in the tank.... and so it may be a bit explosive when the cap is removed. very dangerous considering the hot scalding water....

    at sea level, water will boil in an uncapped radiator at 212degrees F.... one would think that should be a good buffer for an engine that is supposed to be running somewhere between 160 and 180 F.... but it isnt.

    some science here if you are wondering why....
    on an un-capped, un-pressurized system, the cylinder walls inside the engine that are exposed to the coolant WILL actually boil the water at that point when the engine is running hard, but its only at that point that it boils. for all the people that dont know how the system really works, it all looks like a normally operating cooling system.... BUT its not. the boiling effect at the cylinder walls will prevent the water from fully contacting the cylinder wall long enough to be able to absorb the heat and carry it away to the heat exchanger..... so the engine will continue to heat up until the entire system is boiling, and/or something gives.....

    BUT, with a pressure cap on it....

    at regular atmospheric pressure at sea level, water boils at 212degrees.... but when you pressurize the system, it prevents the boiling of the water til it reaches slightly over 251 degrees.., which keeps the system more stable and allows the water to fully contact the cylinder walls, absorbing and carrying away the heat build up.... a 41 degree change doesnt seem like much, but it is to the life of the engine...

    regular pressure cap ratings are from 6 to 19lbs, which one you should use depends on the system needs......

    .........on my vehicles and boats, I keep the recovery tank between the hot and cold marks when the engine is cold, checked before start up....





    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

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      #17
      Never run H2O only in your Closed Cooling System!
      A closed cooling system will be using an E/G and H2O mixture.


      Right you are....... at sea level, just plain H2O will boil at 212°F, and a proper mixture of E/G and H2O will boil near 224°F.

      And right you are again........after taking cooling system pressure into account, a proper mixture of E/G and H2O will hold off from boiling until around 256-260°F.
      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


      • Metrodriver
        Metrodriver commented
        Editing a comment
        Is that the same as 100C for those of us that hate F?

      #18
      I'm using QuickSilver's coolant (the "recommended" for the engine).
      Unfortunately I seem to have some issues with my cooling. There seems to be a slight discoloration to the coolant at the top of my heat exchanger. Also, it keeps pulling in coolant from the overflow bottle, it never increases while hot.

      When I bought the boat and wasn't too familiar with what to check for each trip, I did notice after a few trips that the heat exchanger wasn't topped up.

      When I replaced the coolant, it got darker and darker the more I drained out.

      It's always full now, but of course draining from the overflow bottle after stopping. Where could my issues be? Could it be the heat exchanger alone, or a lot of more problems? Could my engine be running with saltwater in it and now have start having multiple failures? 😥

      Comment


        #19
        Originally posted by builderdude View Post

        The last one pictured actually pulls from the bottom of the tank, you can barely see the connection at the bottom left. The outlet at the top is a vent as the cap is somewhat sealed with no dip tube.
        Same one I have.
        Exactly. That's the one I have. The top outlet is just a tube hanging on the side, and will dispose to the bilge if it gets full.

        Comment


          #20
          Glenn, coolant will expand and contract, causing a transfer of coolant between the Heat Exchanger's tank and the recovery reservoir.
          The pressure cap must be correct for this system.


          As per the thread title: Should I add coolant to overflow container?

          No coolant should be leaving the system.
          If it is leaving the system, you may have an internal leak..... either within the engine or within the Heat Exchanger's tube bundle.

          If the leak is within the engine, you can use Hydrocarbon Test strips to see if any combustion gasses are entering the coolant.
          You can also perform a cylinder leak-down test.
          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


            #21
            Originally posted by DIYglenn View Post
            I'm using QuickSilver's coolant (the "recommended" for the engine).
            Unfortunately I seem to have some issues with my cooling. There seems to be a slight discoloration to the coolant at the top of my heat exchanger. Also, it keeps pulling in coolant from the overflow bottle, it never increases while hot.

            When I bought the boat and wasn't too familiar with what to check for each trip, I did notice after a few trips that the heat exchanger wasn't topped up.

            When I replaced the coolant, it got darker and darker the more I drained out.

            It's always full now, but of course draining from the overflow bottle after stopping. Where could my issues be? Could it be the heat exchanger alone, or a lot of more problems? Could my engine be running with saltwater in it and now have start having multiple failures? 😥
            Glenn, are you saying the system keeps pulling coolant from the overflow reservoir and your continually having to add coolant to keep it at the cold mark? You may want to test the coolant for combustion gasses or do a leak down test as Rick mentioned in the previous post.
            Basically once the system has bled off any excess air you should not need to add coolant. If your continually adding coolant to the overflow reservoir to keep it at the cold mark there’s likely a problem.
            Dave
            Edmonds, WA
            "THE FIX"
            '93 2556
            Carbureted 383 Vortec-Bravo II 2.0:1 18 1/4x19 P

            The rebuild of my 2556 https://www.baylinerownersclub.org/f...76?view=thread
            Misc. projects thread
            https://www.baylinerownersclub.org/f...56-gctid789773

            Comment


              #22
              Yup. It has probably run a total of 3-4 hours since changing coolant, so there might be an issue here. I contacted the local mechanic, and he said if I'm losing coolant and it's not in the bilge, the engine is done. I probably have saltwater in the system and should purchase a new Volvo engine (he gave me a 60k price) and said all Mercruisers post 10 years are garbage and I should probably not care to repair it.
              I guess saltwater in the coolant will destroy the engine, but I didn't know it could be this bad...?

              Comment


                #23
                Glenn, we will typically see these areas whereby the coolant has a means of disappearing (i.e., being consumed):

                1..... the heat exchanger's tube bundle is leaking, allowing coolant to escape via the seawater side of the tube bundle.

                2..... cylinder block crack.

                3..... cylinder head crack.

                4..... cylinder head gasket failure.


                # 1 is pretty tough to detect.

                With #'s 2, 3 and 4, coolant may show up in the engine oil, or..... depending on the location of a crack or gasket failure, coolant may also enter a cylinder and go out with the exhaust gasses.


                It will be fairly easy to remove the heat exchanger and take it in for a pressure test.

                As for the engine, a cylinder leak-down test is about all you can do.
                This will be a cylinder leak-down test, NOT your basic cylinder pressure test (aka compression test).



                .
                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


                  #24
                  Originally posted by DIYglenn View Post
                  I contacted the local mechanic, and he said if I'm losing coolant and it's not in the bilge, the engine is done. I’d disagree with that. The closed system is under pressure during engine operation, that pressure would likely keep any saltwater from entering the system. As the engine cools down it could pull in some salt water only if the lose of coolant is heat exchanger related.
                  I guess saltwater in the coolant will destroy the engine, but I didn't know it could be this bad...?Salt water mixing in with the coolant isn’t the greatest, but if caught early it would likely have little long term impact. There’s a large percentage of these boats that are raw water cooled, nothing but salt water for coolant.
                  Before you go shelling out 60k I’d recommend you have someone perform some testing. As Rick stated above, the HE can be pressure tested and a leak down test can be performed as to verify what cylinder(s) may be causing the lose.
                  You may find out it’s just a head gasket?
                  Dave
                  Edmonds, WA
                  "THE FIX"
                  '93 2556
                  Carbureted 383 Vortec-Bravo II 2.0:1 18 1/4x19 P

                  The rebuild of my 2556 https://www.baylinerownersclub.org/f...76?view=thread
                  Misc. projects thread
                  https://www.baylinerownersclub.org/f...56-gctid789773

                  Comment


                    #25
                    All too often today's mechanics are Parts Changers.

                    If your mechanic is NOT suggesting to have the H/E tested, or to perform a Coolant Hydro-Carbon test, or to perform a Cylinder Leak-Down test.......... I'd find a new mechanic...... a real mechanic.
                    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


                    #26
                    Thanks guys!
                    Im checking with someone that sells Mercruiser parts now. (Volvo is the only deal around here it seems).
                    He seems like a nice guy and wanted to check with some experts what the test steps should be.

                    He said “well, I could also tell people to swap their engines, but then I wouldn’t really be offering a good service would I?”

                    The oil is pitch black, no traces of anything when I did an oil change last autumn either.

                    The engine runs like a clock, never any issues. It’s sometimes a bit sluggish to pull around, then starts on the first beat of the starter. But I think that’s the battery’s fault. If I connect both 1+2 it usually starts immediately.

                    I’m currently replacing the electronics including charger, so batteries is the last step, making sure they receive the best possible charging.
                    The negative cable connector is slightly corroded as well, so it could be the culprit.

                    Comment


                      #27
                      Sounds like the engine performs well. Id take a look at the spark plugs, that’ll possibly show signs of coolant being consumed during combustion. If things look normal there than your HE may be the reason for the loss of coolant. If so no new engine needed.
                      Dave
                      Edmonds, WA
                      "THE FIX"
                      '93 2556
                      Carbureted 383 Vortec-Bravo II 2.0:1 18 1/4x19 P

                      The rebuild of my 2556 https://www.baylinerownersclub.org/f...76?view=thread
                      Misc. projects thread
                      https://www.baylinerownersclub.org/f...56-gctid789773

                      Comment


                        #28
                        ...........
                        Originally posted by DIYglenn View Post
                        Thanks guys!
                        Im checking with someone that sells Mercruiser parts now. (Volvo is the only deal around here it seems).
                        He seems like a nice guy and wanted to check with some experts what the test steps should be.

                        He said “well, I could also tell people to swap their engines, but then I wouldn’t really be offering a good service would I?”

                        The oil is pitch black, no traces of anything when I did an oil change last autumn either.

                        The engine runs like a clock, never any issues. It’s sometimes a bit sluggish to pull around, then starts on the first beat of the starter. But I think that’s the battery’s fault.
                        If I connect both 1+2 it usually starts immediately.

                        You should not need to select ALL/BOTH to start the engine!
                        If you do, it may indicate:

                        ..... starting battery needs to be replaced
                        ... weak Negative connection on the start load batt bank
                        .... Perko 90* sweep MBSS (light contacts and weak contact spring)


                        I’m currently replacing the electronics including charger,
                        Suggestion:
                        Run a fresh new dedicated circuit forward for your electronics. Both Positive and Negative.
                        Install a dedicated circuit breaker panel for the electronics.

                        This will take the load from the OEM engine harness and hull harness.


                        so batteries is the last step, making sure they receive the best possible charging.
                        The negative cable connector is slightly corroded as well, so it could be the culprit.
                        Possibly!
                        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


                        • DIYglenn
                          DIYglenn commented
                          Editing a comment
                          Thanks!! I had not considered the MBSS, which also could be an issue. I’m replacing this as well.
                          A lot of the electronics are being moved away from the original harness to its own fuse box, so hopefully spread it a bit more and as you said, reduce the load on original harness.
                          I’m removing/reducing unnecessary power draw else on the boat. Everything light is now LED etc.

                        #29
                        I guess I at some point should’ve written my engine model:
                        It’s a 2005 CMD Mercruiser 4.2L 250HP.
                        Last series before QSD (white) I believe.
                        Electronic injection, but manual controls.

                        Comment


                          #30
                          Hi again!
                          I’ve found someone who knows these engines. He said the heat exchanger sounds very likely on this particular engine, probably because of frost and a cracked tube.
                          He offers a service where I can send it in and have it welded (replace broken tubes) and painted etc so it’s like new for $1.500.

                          I’ll see if I can remove the side covers and use a mityvac to pressure test the tubes. If I find a leak, I guess I’ll just send it off.

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