Taken from another thread on another board but equally applicable here:
[You can clean your cooling system yourself with cooling system cleaning products sold at auto parts stores]. Prestone "Super Radiator Cleaner" is one product that'll do so. So is Solder Seal/Gunk "Heavy Duty Radiator Cleaner". The "fast flush" types of products are not what you need.
Once you've cleaned out the system, rinse it twice as thoroughly as called for (make sure the heater valve is fully open while you do the cleanout job), drain thoroughly and fill with 50/50 coolant and distilled water. Pick your coolant carefully; don't use anything that mentions being Dex-Cool compatible. The newest G-05 formulations are a good choice, but if you can find conventional green silicate-based coolant (getting scarce!), that's fine, too. There is no need or advantage to adding anything to the coolant in the way of other chemicals or additives.
