Steve99, I will give that a try and see if it cleans things up.
KLUTZ, Obviously, this problem doesn't affect every GM car, although it seems to hit Blazers and s-10 trucks more than passenger cars. After more research it appears the sludge develops quickly if air is allowed in the cooling system. So how does the air get in the cooling system? Some Blazers have developed leaks in the intake manifold gaskets (Is that a design problem or a coolant problem?). Others have had failed radiator caps that allow air to get into the system (Is it a bad cap or does the sludge stop the cap from sealing properly and let in air?). On my car the overflow tank had water/coolant in it and was checked regularly. However, there was a small shortage of coolant in the radiator itself, although the car only registered hot once right when we discovered the problem. Of course, you are not suppose to remove the cap if the car is warm, so perhaps the radiator itself wasn't checked as frequently as the overflow tank. I don't know why the system lost fluid, maybe a bad cap, but it did. In any event the sludge has ruined radiators, heaters, engines, and automatic transmissions (transmission cooling lines run to the radiator and guess what?? get plugged by the sludge). At this point I hope to be able to flush it out and that no real damage has occurred. However, a google search has provided me with enough horror stories that I may want to look for another car. Interestingly, my 2000 S-type Jaguar uses dex-cool antifreeze without any reported problems that I know of. So perhaps this is limited to some GM products due to a varity of causes. From what I hear, GM is stonewalling on the issue (remember the side saddle gas tanks in GM pick ups) especially if the vehicle is out of warranty. There are at least eight class action law suits filed.