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    Diagnosing bad heat exchanger

    Hi All, I'm commenting here since coolant leaks can be very frustrating (as we can see from the various posts). I'm not a mechanic but will tell you what we found on our Mercruiser 5.7L (1989 Carver). The temp would stay within range as long as we were cruising at around 1,750 RPM. When we...
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    Diagnosing bad heat exchanger

    Hi Jeff, I have a similar problem to what Steve describes…how do I diagnose an air leak on the intake side of the circulation pump? Thanks, Dave
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    Diagnosing bad heat exchanger

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    Losing coolant on engine cool-down - 1989, 5.7L Mercruiser

    The air leak would make sense but we never saw any dripping water from the circ pump area or coolant in the bilge. I'd think when the engine was hot and shut down, we would either see a coolant leak at the circ pump, hear hissing air, or smell coolant steam.? We did run a heat exchanger...
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    Losing coolant on engine cool-down - 1989, 5.7L Mercruiser

    I've owed the boat for a while and had the engine rebuilt so if there was some 'foreign' substance in the coolant, it would have been from me or the engine installer....it's just a weird scenario and I hope it's resolved. Thanks for the comments.
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    Losing coolant on engine cool-down - 1989, 5.7L Mercruiser

    Hi All, I wanted to thank you for the input and report an update. I 'think' the engine is repaired. Neither the mechanic nor I have a perfect explanation however, here's what happened. We hooked up a garden to hose the seawater intake and ran to temp at various RPM. It has a closed cooling...
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    Losing coolant on engine cool-down - 1989, 5.7L Mercruiser

    Thanks very much, I appreciate it. I assume a pressure test would help diagnose a heat exchanger leak. I’ll have to read about how to properly perform a pressure test. Do you know…when you pump up the pressure (I assume to about 15 PSI), if it leaks out, how do you know where it is leaking...
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    Losing coolant on engine cool-down - 1989, 5.7L Mercruiser

    Thanks so much for your reply! The head and block were not checked for flatness after the failed head bolt and replacement gasket. I hadn’t really thought of that. We probably should have done that when we had the head off since the head is portable. Can the block be tested for a warp while...
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    Losing coolant on engine cool-down - 1989, 5.7L Mercruiser

    Hello, I've read the forums and will do a pressure test next. The problem: I have an 1989 28' Carver Voyager that has rebuilt 1989 5.7L Mercruisers (gas). Unfortunately, the port rebuild has had lots of trouble so I have kind of lost track of what was fixed/replaced when. We recently had a...
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