I've used products like the radiator flush you have in mind with little visible success. I recently got a Mustang running for my pastor that hadn't been started in 20 years. I ran the cooling system flush through, old style agressive stuff, then the neutralizer, the coolant was still very brown and rusty. I flushed it twice more with straight water and it was still pretty brown. I'll be flushing it again at every oil change until it is no longer rusty.
Devin
