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Closed Cooling Heat Exchanger

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Hi Everybody,

2019's maiden voyage was cut short by an overheating LS1.  When I lifted the motor box there was coolant in the bottom of the bilge.  As we limped back to the trailer I was unable to identify any leaks.  The impeller housing was nice and cold and I checked the oil to be sure it didn't contain any water in the coolant.  Unable to figure out the problem myself I took it to the professionals.  I get the call on it today and they think the problem is most likely an internal leak inside the heat exchanger.  They quoted me $1,500 for the part plus labor so I'm kinda bummed about saying good bye to 20 Ben Franklins.  I am confident the plugs were pulled from the exchanger because I just put them back in the other day when we took the boat to the lake.  Having said that, I don't remember the act of doing it so I guess it could have been plugged up in a way that didn't let all the water drain out but I would think there would have been overheating problems last year if that was the case.  Anyhow, any thoughts on this diagnosis, and assuming it's correct, what could have been done to prevent this?  Is it possible that it "just cracked" even if no water was in it? Don't want to relive this. 


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The exchanger has coolant in its interior tubes and raw water around them.  It's probably a good idea to make sure that all of the raw water is out.  I don't need to winterize where I live,  but if I did, I would remove the raw water hoses from the exchanger and the raw water pump and make sure everything is empty. 


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And by the way, why don't you change it yourself?  It should be very straightforward, and you will learn how it works. 

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Thanks for the tips.  I'm doing some due diligence on the price of the part before I give them thumbs up to start the repair.  If I can get it significantly cheaper I  may take a shot at it myself, but I haven't been able to find it online.  Waiting on a call back from Discount Inboard Marine.

What I don't understand is that if it's leaking inside the heat exchanger then how did the coolant get to the bilge?  I'm going to ask them if they're sure it couldn't just be plugged and also be sure they confirmed that it is not the thermostat.  I've winterized it myself every year since it came home in '06 with no problems, but maybe I just had a lucky run.  They told me they saw this one other time.

Thanks again guys.

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I've removed mine on a v-drive (easier if you have another set of hands helping) but totally doable.   Once you have it off you can inspect it yourself.  Run water through fresh water side and see if there are any leaks you can see.  What about the end cap seals?  Could those just need to be replaced?  

I found out from Bakes that the company that makes all the Indmar heat exchangers (at least for my years Indmar) is http://www.mrcool.us.  I called them and they were super helpful even though my heat exchanger ended up being fine.

Hope that helps

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