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To further a previous post…
Ran the boat in our annual Xmas parade. Boat ran fine an most of the night was spent at idle or under 1000 rpm. Upon return I found coolant leaking into the bilge from the coolant in pipe to HX after thermostat. The plastic overflow tank was full upon return and some of the coolant returned to the engine once cooled. I figured it was the leak that caused the plastic tank to fill.
I fixed the leak by draining down the coolant, removing the pipe between the HX and the t stat and replaced all the o rings. No more leak.
I refilled the coolant and ran the boat with the coolant cap off and noticed bubbling at the neck of the expansion tank on engine. See video
I tested the HX under pressure and it held. I tested the coolant for salt intrusion and none detected.
Ran the coolant test on both side with the same results.
My fear is my cooling system is building pressure from exhaust causing the bubbling and the overflow/leak from pressure build up in the expansion tank.
I have owed the boat for a year and have never had an overheat. Able to make full rpm, within fuel curve and overall it has been flawless.
Looking for my next step to rectify.
Thanks.
Mike
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We have a QSC500 and FWIW I can confirm that it takes quite a few engine hours after a coolant change before the level settles. Last time we did this I was actually about to take the turbo off as I suspected loosing coolant through the infamous exhaust to turbo gasket…when the “loss” of coolant finally stopped.
However your initial problem seems more to have to do with building pressure in the cooling system. No experience with that on our Cummins. However I once had the same problem on a CAT 3208TA that was blowing out coolant and building pressure into the expansion tank. Very long story short this appeared to be a deformed headgasket ring on 1 cylinder that would leak a very tiny bit of compression pressure into a coolant channel.Cheers, André
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A few bubbles may not be a problem when run this soon after a drain down. There may still be an air pocket or two stuck somewhere.
Just idling may not expel that air. Bump the revs up, approx. 1200 -1300 revs which will increase flow helping to move the air.
Then I think I would take the boat for a mild run to fully heat the engine which will move the air pockets. Let cool down and remove the cap and check again.
There are also tests fo exhaust gasses that can be done.
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