Coolant complete change - Do I need drain and fill with wather to flush?
 

Hi guys,
I have no idea when my Forester 2006 got its coolant changed (if it was changed ever), so I am going to change it.
I am considering draining and filling the radiator a few times with the distilled water and letting the engine run with the heater for 15-20 min between each drain\fill. Do you guys do this kind of procedure?
I just would like to flush the system and heater core specifically. I am also considering adding some cooling system cleaner for the first run, like this one https://prestone.com/product/preston...ystem-cleaner/
What do you think?
Please advise.

Personally I just disconnect various hoses and run the hose pipe through until it's clear. Mainly Radiator, heater.The block/heads is probably the only thing that'll need drain/refil/drain unless you remove the thermostat.

By all means use a cleaner if what's in there looks mucky. Usually caused by mixing antifreeze types or air/cavitation combined by OAT antifreeze which causes sludge (usually caused by a slightly weepy water pump that sucks in a bit of air when starting from cold).

How many times depends on how mucky it is. Personally I'd use tap water unless you live in a really hard water area. And use the distilled (not deionised) water on the final fill.

Recommend a vacuum filler to avoid the inevitable air locks.

Thank you for the reply.

I am going to replace the timing kit with the water pump and thermostat, and will also install a block heater (as I live in a 'cold' province in Canada). So will drain all the coolant from the engine block and will remove the radiator during the procedure.
I just would like to clean the cooling system as I imported the car recently and don't know when the coolant was changed last time, if it was changed ever. It's a green color coolant and it is not looking bad, however, want to flush and clean the heater core before winter comes.

So flushed with the radiator 6 quick drains and fills. Came out first the green fluid and 6th time I was clear water came out. No additives used, just distilled water only.

And what are you going to use for final fill??

https://cimg6.ibsrv.net/gimg/www.sco...edd47c0820.png
or SOA868V9270

That is exactly what I used.