It's a long time since this post has seen any action but I have to say The Method Works!
I got quite a bit of the brown residue out with a bottle brush (It was nowhere near clean though!)
then followed with an overnight soak in hot water with dishwasher soap. Then a good rinse followed by the shake with a mixture of
bleach and rice (Basmati
)
The only thing I would add to the instructions is, if you have a coolant level float in the tank to make sure that it isn't stuck in place with
grains of rice. I also covered the cap opening with plastic wrap to keep rice out of the valve. One other tip.....I used the pointy ends off tubes of sealant to plug the holes while shaking. (All but the smallest one which I plugged with a finger.) It saves getting bleachy rice all over the kitchen.