What i did with mine was removed the aluminum rad and replace with the old stock single core unit.
Put your heavy duty rad flush in and run/ let sit for the week.
FLUSH THE CRAP OUT OF IT .
Connect your garden hose to the heater hoses and flush flush flush.
Take your rad and FLUSH IT WELL.
After all said and done... REFILL.
Use a good quality anti freeze.
In a separate 20 litre bucket, pour in your anti freeze. Then with an equal amount of DISTILLED water (its cheap, so dont cheap out) pour that amount in and mix thoroughly.
(i used 2 jugs of antifreeze and 2 jugs of distilled)
ROYAL PURPLE has a anti freeze additive that is awesome. also lowers the boiling point of the water. Pour that in first.
Then fill your cooling system to the max. Run engine to burp the air pockets but keep adding fluid until you feel positive that there is no more air.
Cap it and then pour 1 litre into a coolant reservoir.
Good luck. Process has always worked for me.
If you are getting recurring rust, your system is not air tight. Rust will only occur when metal contacts liquid then dries.
