Thread: Coolant Problem
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Old 05-23-2022, 06:02 PM   #2
Lepke
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City: Between Oregon and Alaska
Vessel Name: Charlie Harper
Vessel Model: Wheeler Shipyard 83'
Join Date: Jun 2016
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It's not uncommon for an air bubble to form under the thermostat if it doesn't have a small hole to allow air to pass. Some engines don't completely fill places where air pockets form without some effort. Larger better designed engines have a bypass circuit that allows some coolant to bypass the thermostat so there is always minimal circulation.

When I fill an empty engine, I start with the known capacity and if necessary work out the air until I've added near that amount of liquid.

Finding the source of the gunshot will require careful inspection of cast parts. I guess there's a crack somewhere if the engine was the noise source. If there were air pockets stopping circulation, some coolant could have turned to steam. Water expands 16x when becoming steam, building pressure rapidly. In an enclosed space it can cause an explosion like a boiler.
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