Buick/Olds: Dexcool, coolant level, evaporation rate

Question
Hi Harold,
I have a 2003 Buick Century with a 3.1 motor and 37,000 miles on it. I bought it in Feb with 25,000 miles on it. I recently noticed the coolant level in the overflow tank was low or empty (hard to tell) so I opened the radiator cap and looked inside, the fluid level was about an inch from the top, but I noticed a little bit of brown/rusty colored sludge on the cap and the wall of the neck looked like it was coated with a rusty colored slime. I started looking on line and noticed that there are a lot of GM owners that have this or similar problems with Dexcool and have had bad experiences with their cooling system. One guy said to just wipe the cap and neck clean and make sure the overflow tank stays to the full mark. Do you recommend I bring it back to the dealer to get it flushed? Thanks Bill  

Answer
Most of the sludge that you are seeing is from leftover sand from the casting process. It will not hurt any thing and you can just wipe it out and top off the coolant level.
Also Dexcool has a higher evaporation rate than the old green antifreeze, so you will need to add some to the system more often that before.