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  1. #1

    Default Coolant out exhaust

    Although the starboard engine cooling system was giving me fits until last weekend (new raw water pump, new thermostat, sealed leaking raw water strainer), the port engine on my '78 Silverton was running cool and losing no fluids - until last weekend. Just when it looked like I had a squared away engine room, I noticed greenish discharge from the exhaust water on my port engine. On my next fluid check I found low coolant on the port engine.
    I topped it off and at the next startup I found a greenish discharge again. I did a cooling system leak test and it held 15 lbs. for at least 15-20 minutes. But when I removed the heat exchanger end cover during the test I got green tinged raw water out of it. I would assume that even though the leak test didn't show a pressure loss, the heat exchanger is leaking and needs to be replaced (it looks rather dodgy). But is there another source of coolant loss into the exhaust I should look at?

  2. #2
    Join Date
    Jun 2006
    Location
    Spotswood, NJ, USA
    Posts
    4,802

    Default Re: Coolant out exhaust

    not if its mixing in the raw water side of the exchanger

  3. #3
    Join Date
    Mar 2007
    Location
    West Hartford, CT,
    Posts
    69

    Default Re: Coolant out exhaust

    Swampee,

    True about raw water mix in heat exchanger. But if pressure came up good on system, H-X may not be the culprit. Re test pressure in system with raw water hoses disconnected from heat H-X. Look for coolant. If coolant is present (leaking) I doubt that you'll see pressure come up. If this is not the case:

    Is your engine full or partial fresh water cooled? If full - meaning manifolds have coolant running through them, not raw water - you likely have a failed gasket between manifold and riser. If it is a partial system, I suggest you perform a compression test of the cylinders. If one is very low, likely a failed head gasket or crack in cylinder head.

    Good luck, Noel.
    Last edited by noelct; 09-09-2018 at 06:13 AM.

  4. #4

    Default Re: Coolant out exhaust

    Quote Originally Posted by noelct View Post
    Swampee,
    Is your engine full or partial fresh water cooled? If full - meaning manifolds have coolant running through them, not raw water - you likely have a failed gasket between manifold and riser. If it is a partial system, I suggest you perform a compression test of the cylinders. If one is very low, likely a failed head gasket or crack in cylinder head.
    Good luck, Noel.
    I'm 90% sure the manifolds are raw water cooled, but I can recheck the lines going to them to make sure.

    I did a compression check on the stbd engine and I did not find the low cylinder I was suspecting. I didn't test the port engine however, since I wasn't having an issue at that time. I've been tempted to go buy a kit for testing for exhaust gases in the cooling system. Supposedly a good indicator of a blown head gasket even when compression checks show ok.

    At this point I'm planning to just pull the port heat exchanger and bench test it for leaks. Really not too difficult (4 hoses and a mount) and since I've replaced most of the lost coolant with straight water, draining the fresh water cooling system is no big deal.

    The season is near end and I'm planning to pull out early this year to concentrate on fall home repairs. I'd rather have the heat exchanger/coolant loss issue sorted before it's winterized.

  5. #5

    Default Re: Coolant out exhaust

    Just to follow-up and bring this thread to a conclusion, I ended up pulling the port heat exchanger and pressure testing it dry. It was leaking for sure. Not sure why it didn't fail the pressure test in situ , maybe because the raw water side provided enough back pressure to equalize things.
    What I noticed was that, I wouldn't lose any coolant as long as the engine was running, only when it sat. Which told me that the raw water pump was probably keeping the fresh water side full - and mingling salt water through the engine cooling system. So before I refilled the coolant, I flushed it out really well with fresh water until it ran fairly clear.
    With everything back together, it shows no coolant loss and runs nice and cool - too cool (120-140 deg.). I suspect the P.O. may have removed the thermostat, so I'll be checking into that after I pull the boat for the winter.

    Meanwhile, back to the stbd engine coolant overflow issue. I'll be doing a compression test to see if I have a blown head gasket...

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