How to flush F/W cooling and water heater coolant?

[hlev00]

I have a Yanmar 4JH4E. Our hot water is heated by the engine. There is a petcock at the back of the engine and there is a tube attached to it. I expect if I drain from there with the 12 degree rake of the engine most of the coolant will drain from the engine. There is another at the front of the engine I would check too. But that still leaves the hoses and water heater heat exchanger full. I have seen a few suggestions to add a tap to the fresh water hose somewhere to attach a hose like in a car. That would leave the system full of tap water and doesn't help me get premix or distilled plus concentrate back in.

Another says 1 drain, 2 fill with distilled, 3 repeat several times. Then 1 drain, 2 add full strength, 3 repeat until up to 50/50. Seems like I would go through a lot of coolant that way.

My searches have not turned up a solution. I expect I am missing something obvious.


The photo is the lines to the hot water heater. Is the tap here for bleeding air since it is at the highest point?

Thanks for your help
Harry

[a64pilot]

I installed a prestone flush kit into one of those water heater lines, that way I can flush the entire cooling system, engine included. Then when you only have clean, clear water coming out, stop and drain as much as water as you can.
If you know cooling system capacity you can then fill with pure antifreeze until you have the correct amount, then top off with water. Example if capacity is two gallons, put one gallon of pure antifreeze in, then add water, that puts you at 50%.

I don't worry about it, I end up with well more than 50% with no harm, and I don't use distilled water, clean clear drinking water is clean enough.
Yes your tap is I'm sure to belle air out.

[hlev00]

Thanks for the idea.

Where do you drain from when you are putting water in through the flush kit tap?