Air Lock in Engine Coolant System

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AMCarter3
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Air Lock in Engine Coolant System

Post by AMCarter3 »

I recently changed the coolant in both engines. After running each engine for 30 minutes at 1000 rpm, both seem fine -- temp gauge ran up to about 125 or so and held there. HOWEVER cold air was still coming out from the heater coil & fan under the entry door steps. So, I'm assuming there is an AIR LOCK somewhere in the 2 long hoses from/to the engine that feeds hot coolant to the heater. The two hoses (outflow and return) are at least 16’ to the heater. That’s a lot of coolant. And there are no relief valves where the hoses connect to the heater to release air. My diesel tech said “Either crack open the hose clamps one of the hoses and bleed the air, OR take the boat out and run it for 30 minutes at high RPM’s (2500-3000). He says the latter usually works to force coolant into the heater and slowly purge the air.

Has anyone encountered this issue and solved it?
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4JH3 Coolant Flow.jpeg
Mac Carter
2006 34' PDQ PowerCat "All Heart"; MV 98; twin 100 HP Yanmars
Home Port: Bellingham WA 98229
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