Overheating

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  • Unregistered Guest

    #1 Unapproved

    Overheating

    My A-4 has been overheating somewhat sporadically. It seems like it pumps water when first started, and then water flow reduces to zero flow, although it does not happen all the time.

    A friend advised me to flush the block with muriatic acid, which I did, but the problem persists.

    I'm afraid my water pump impeller shaft may be scored, but I didn't think that could cause the problem as the impeller vanes are in perfect condition.

    Also wondering if this could be attributed to the exhaust manifold.

    Any ideas you could give me would be appreciated. Thanks for your help.
  • Don Moyer
    • Oct 2004
    • 2806

    #2
    Here is a recent response to a frequently asked question (FAQ) on the subject of overheating that should be helpful for you. Within the context of this FAQ, I recommend that you treat your situation as one in which your total flow is not normal.

    Q: My late model engine overheats intermittently. Is there a systematic method to start troubleshooting the cooling system?

    A: Check first to see if you have a normal flow of cooling water coming out of the exhaust.

    NOTE: A normal flow of engine cooling water will usually be sufficient to build up a head within the water lift muffler at idle, to overpower the exhaust pressure, and result in a "batching" of the water out of the exhaust every second or so.

    If you have a normal flow of water out of the exhaust, you would have to look for a restriction that is preventing water from entering your block through the "T" fitting in the center of the water jacket side plate. Examples of this kind of restriction are things that can prevent water from passing through the "T" fitting in the center of the water jacket side plate, or perhaps a thermostat that is stuck in the closed position. You can troubleshoot this possibility further, as well as get some short term relief, by clamping the bypass loop partially closed with a small "C" clamp. The bypass loop is the hose between the "T" fitting in the center of the water jacket side plate and the inlet to the thermostat housing.

    If you do not have normal flow of water through the exhaust system, you will have to look for a restriction in a location that can limit the total flow of water. Examples of these restrictions include a blocked raw water through-hull, a piece of broken impeller in the elbow on the outlet of the water pump, a clogged manifold, a blockage in the inlet fitting to the exhaust system, etc.

    Feeling the temperature of the water leaving the boat via the exhaust system is not a valid method of troubleshooting the cooling system. In the bypass type of cooling system used in late model engines, the water leaving through the exhaust system is always a mixture of hot engine water and cool incoming raw water, so what you feel is always rather lukewarm.

    Best regards,

    Don Moyer

    Comment

    • taterry
      Member
      • Feb 2005
      • 4

      #3
      Intermittant overheating

      I am also having intermittant overheating. This A4 has been in this boat (Ranger 29) from new and has always been raw water cooled. I've just installed the recommended T valve so I can acid flush and fill the engine with fresh water. Having owned the boat for just two years, I'm not sure if it has ever been flushed. So yesterday, we fed it about 6 gallons of mureatic acid diluted as recommended. We got out a hugh quantity of black goop and toward the end when feeding in fresh water. We go out some green goop. Then the exhaust cleared. I'm wondering what the black and then green was.
      Our overheating occured while we still had exhaust water coming out the back but it was very black and lots of steam.
      Terry in Oakland

      Comment

      • Don Moyer
        • Oct 2004
        • 2806

        #4
        Terry,

        Regular flushing of Atomic 4 engines was apparently so rare in past generations that you're probably correct to assume that yours has not been flushed during its 25 to 30 year lifetime. This means that the crud in your cooling jackets was a combination of so many minerals, sediments, and bio-growth that it would be virtually impossible to quantify it without a very sophisticated chemical analysis.

        Unless you have a particular interest in the chemical make-up of things, I'd be more than content to know that, whatever it was, it's now out of your engine, and regular flushing will keep the cooing jackets free of further build-up during your watch.

        With respect to overheating, while you observe a normal flow of water out of the exhaust, you would have to look for a restriction that is preventing water from entering the block and preferentially moving through the by-pass hose instead. Examples of such a restriction are a blockage within the "T" fitting, blockage in the diverter cap inside the center of the water jacket side plate, or a thermostat that is stuck in the closed position.

        NOTE: The bypass loop is the hose between the "T" fitting in the center of the water jacket side plate and the inlet to the thermostat housing.

        You can troubleshoot the extent of a blockage in this location, and get some short-term relief, by clamping the bypass loop partially closed with a small "C" clamp.

        If the flow of cooling water out of the exhaust reduces significantly as you clamp off the by-pass hose, the restriction would be quite serious and will probably require removal of the water jacket side plate and/or or the thermostat for further inspection, cleaning, or replacement. In the case of lesser restrictions, one of our customers was able drill an 11/32" hole through the center of the "T" fitting and tap it with 1/8" pipe threads. He was then able to connect a hose to pressure flush the "T" and diverter cap to restore good flow. After flushing, he installed a 1/8" pipe plug in the hole he drilled and tapped in the "T".

        Best regards,

        Don Moyer

        Comment

        • taterry
          Member
          • Feb 2005
          • 4

          #5
          Thank you for your comprehensive reply Don.....I'll clamp off that hose and see what happens and I'm going to give it another flush after our first cruise out on Feb. 25.
          After sailing from now on, I'm planning to give the engine a fresh water flush and leave fresh water in it. I dread having to take the side plate off but the thermostat housing would not be too bad. Access in the Ranger 29 is terrible!!
          Cheers
          Terry in Oakland

          Comment

          • JAWS11
            Member
            • Oct 2004
            • 3

            #6
            Over Heating

            If You Have A Raw Water Strainer Check The Gaskets On The Strainer I Have A 1979 28ft.newport And That Was My Problem With Overheating It Was Getting A Little Air In The System If You Have A Above Ground Swimming Pool And You Get A Little Air In The System You Will Notice You Do Not Have The Right Pressure That Is Just What The Engine Is Doing

            Comment

            • Dick Roberts
              Member
              • Jun 2006
              • 4

              #7
              How exactly do I flush?

              I have a C&C Corvette and the A 4 has been running like a Swiss Watch for years. This year it has been overheating and I have read the advice in the forums, and I've concluded that it needs a flush. But how do I get into the block? Can I go through the thermostat hole?(which is now open because of about to change thermostat). How step by step do I go about it please, in otherwords where does the flushing solution go in and where does it go out and which plugs do I need to remove??
              I'd apprecaite an answer, Don, my boat is calling for some excercise.
              Thanks.
              Dick

              Comment

              • Jim Booth
                Senior Member
                • Jan 2005
                • 151

                #8
                I posted a couple pictures of my setup for flushing the motor last year. Search for a thread title "T Fitting in Water Intake".

                Jim

                Comment

                • Don Moyer
                  • Oct 2004
                  • 2806

                  #9
                  Here's the link to Jim's pictures.

                  Don

                  Comment

                  • Don Moyer
                    • Oct 2004
                    • 2806

                    #10
                    Dick,

                    Attached find the "text only" versions of the flushing procedures in Chapter 2 of our Service and Overhaul manual.

                    Don
                    Attached Files

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