Quick question regarding cooling system bypass?

[nathan007]

Hello!
I have a 3JH4E yanmar , with fresh water cooling (coolant , heat exchanger, raw water intake)

Now I might have to replace the engine coolant Before winterizing the engine, but I will also need to replace the hoses going to the water heater in the spring...

My question, could I simply loop the lines at the engine to make it easier to bleed and get over with it, and have less wasted coolant in the spring? I would simply blow the coolant remaining in the water heater section..

[NYSail]

If you are changing the coolant I would recommend no bypass. A big part of changing fluid is to flush system completely..... not just a drain job. When I changed mine I removed the thermostat, drained coolant, filled with water ran engine for 5 minutes..... repeated until water came out clear. Then put new rhermostat and added nice new shell rotella antifreeze. If you’re going to do the job, do it completely.

Greg

[nathan007]

I totally understand, but in my case time is playing against me.. I haul out tomorrow for winterizing.

I planned on replacing the coolant (only about 1 year old since purchase of the boat) but a few weeks ago I notice the hoses going to the water heater were not looking great , so I planned on replacing them in the spring ( about 16ft of hoses ) before comissionning. This is the only reason I would bypass the heater at this monent.

And, I planned on replacing the coolant in the spring also, with a new thermostat and cap, but last week when tested the coolant density (temp protection) it was way too low (about -25 celcius) for me to leave it this way.

[a64pilot]

Yes, you can do what your asking, without harm.
Just be sure to blow out every bit you can from your heater, you don’t want it freezing and busting.

[Lepke]

Another option is drain all the coolant now. Open the block drains and get all the coolant out. When you buy hose, it may be cheaper to buy a roll on ebay.

[nathan007]

Indeed, but I would like to minimize corrosion risks, I'll probably just do the engine part at the moment

[sailian89]

Originally Posted by NYSail

If you are changing the coolant I would recommend no bypass. A big part of changing fluid is to flush system completely..... not just a drain job. When I changed mine I removed the thermostat, drained coolant, filled with water ran engine for 5 minutes..... repeated until water came out clear. Then put new rhermostat and added nice new shell rotella antifreeze. If you’re going to do the job, do it completely.

Greg

Greg,

I have often wondered about flushing when changing the oil....any way to flush other than using a lot of oil?