Would like some help on the steps/procedures to drain the engine coolant - including what is in the engine. Then how to fill it up without getting air in the lines. I noticed on one of the hoses there is a screw off top for adding coolant. I need to really flush it clean as I want to shoft to Shell Dex Cool. My boat is a Hunter 310 and it has an Yanmar 2GM20 18 hp engine.
Draining & Replacing Engine Coolant
- Thread starter Granfalloon
- Start date
- Status
antifreeze replacement
Having just done this last weekend, I'll try to recount the steps. Please note that if you intend to replace with a different type antifreeze, it is crutial that you thoroughly drain and flush the old green stuff out prior to refilling with Dexcool as the two are not compatible. The thing(s) you describe as "screw-off tops" are likely the petcock drains on the engine to water heater hoses. The only opening with which I am aware on the engine is the cap on top of the heat exchanger. There are either 3 or four drains on either side of the block, probably having clear plastic hoses attached which drain the the engine sump. Open the exchanger cap and all drains to drain the block. Remove both heater hoses and gravity drain as well. The are various methods of flushing as you can imagine; one being refill everything with fresh water and allow to circulate and then drain again and repeat as needed until the drain water is clear. With the heater hoses inverted, refill either one while keeping the ends at the same elevation until the new antfreeze overflows - ensures no entrained air. Refill block at cap as well as overflow tank to cold level. Run the engine up the temp to ensure thermostat opens and circulation is complete; CAREFULLY open hot cap and continue filling until proper level is obtained in both the heat exchanger and overflow tank. Then go sailing ASAP
Having just done this last weekend, I'll try to recount the steps. Please note that if you intend to replace with a different type antifreeze, it is crutial that you thoroughly drain and flush the old green stuff out prior to refilling with Dexcool as the two are not compatible. The thing(s) you describe as "screw-off tops" are likely the petcock drains on the engine to water heater hoses. The only opening with which I am aware on the engine is the cap on top of the heat exchanger. There are either 3 or four drains on either side of the block, probably having clear plastic hoses attached which drain the the engine sump. Open the exchanger cap and all drains to drain the block. Remove both heater hoses and gravity drain as well. The are various methods of flushing as you can imagine; one being refill everything with fresh water and allow to circulate and then drain again and repeat as needed until the drain water is clear. With the heater hoses inverted, refill either one while keeping the ends at the same elevation until the new antfreeze overflows - ensures no entrained air. Refill block at cap as well as overflow tank to cold level. Run the engine up the temp to ensure thermostat opens and circulation is complete; CAREFULLY open hot cap and continue filling until proper level is obtained in both the heat exchanger and overflow tank. Then go sailing ASAP
Screw-off cap
Some owners have installed hose fittings on the water heater input hose to facilitate flushing and filling of those lines. The design accepts a common water hose and allows for an elevated gravity feed to flush and then refill the water heater lines. That is the most common area where air locks form when refilling the cooling system.
Some owners have installed hose fittings on the water heater input hose to facilitate flushing and filling of those lines. The design accepts a common water hose and allows for an elevated gravity feed to flush and then refill the water heater lines. That is the most common area where air locks form when refilling the cooling system.
- Status