I have a 3ym20 yanmar diesel engine on my beneteau 323 (2005)sailboat. I am trying to do more work on it myself. I want to change the antifreeze(fresh water coolant). I know where to drain the system. My concern is developing an air lock. The water heater( in starboard locker) is heated in one of two ways(turn it on at the control panel or when motoring it is heated). I think the antifreeze(fresh water coolant) circulates in a loop to the water heater and heats it when motoring. I have heard that when changing the antifreeze an air lock can develop there. If an air lock develops then the engine can over heat when motoring. If this is the case how do I avoid developing an air lock or correct(bleed) the system? If you have this type of engine and experience please let me know. Thank you.
DIY advice
- Thread starter Mike8193
- Start date
Most water heater loops are located in such a way to be lower than the engine. This is done to allow air to rise up and out of the system. Typically an air lock develops on the top of the engine. The counter this, engines usually have a bleeder at the high point. In general the high point is often located at the thermostat. Look for a bleeder that resembles a wing nut with an orifice in the middle. This would be the bleed. Open counter clockwise and remove the radiator cap and add coolant. Hydraulic laws should allow the coolant to seek it's own level. Depending on layout, the coolant may rise out of the bleed when the level of coolant is at the top of the radiator cap seat. You need to have coolant exit the bleed. If none does, and with the coolant as high as possible in the cap opening, let it stand to see if the level will go down over 10-15 minutes. If not, replace rad cap, and start engine. Be prepared to close the bleed. Once fluid rises out of the bleed, close it and shut down engine. Remove rad cap and note any drop in fluid level. Top off. Repeat this until the level under the cap stay up.
There are many methods for filling & bleeding air from the system. Last time I changed the coolant in my 3YM30 Yanmar, I disconnected one of the heater hoses and filled the system ( with the heat exchanger cap off) using a jabsco hand pump.
Had no air in the filled system to bleed.
Additional note, the bleed valve on my Yanmar is a Presta type valve.
Had no air in the filled system to bleed.
Additional note, the bleed valve on my Yanmar is a Presta type valve.
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Good ideas for filling the system but keep it simple right from the start. Remove the old coolant only from from the engine and leave remainder in the hoses and water heater. Every two years, change the coolant in this fashion and you will not be able to tell the old coolant from the new coolant.
If your present coolant is looking bad, maybe swap out more coolant one or two extra times after maybe 2-3 running hours each time between changes. Don't drain your hoses and water heater coil unless you want headaches for the next little while, most often when you REALLY need your engine
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PS. be sure to use only distilled water when making up your 50/50 coolant.
If your present coolant is looking bad, maybe swap out more coolant one or two extra times after maybe 2-3 running hours each time between changes. Don't drain your hoses and water heater coil unless you want headaches for the next little while, most often when you REALLY need your engine
.PS. be sure to use only distilled water when making up your 50/50 coolant.
Look at the Catalina 34 Owners Group techwiki. Mainesail commented on the airbond issue with how he redoes the bleeding valve to add a ball valve and hose barb connection. I've been doing it that way for 9 years and never had an issue.
Good luck
Good luck