I just bought a brand new G6 GT Coupe and thought I would start this thread regarding the notorious GM coolant "DEX-COOL". Dex-Cool is a silicate-free, orange coolant designed by GM to last 5 years or 150,000 miles. It's a great advancement in engine and coolant technology; however, the early engines that used this coolant developed problems with their gaskets, pumps, radiators, etc due to various reasons and led to a huge class-action lawsuit that was settled last summer 2008. After doing some research, I've boiled the problems down to these few bullet points:
The gaskets were made of a plastic material that was incompatible with Dex-Cool. I am not sure if GM has changed the material with which they build their gaskets; if not, this problem might persist on new engines.
In extreme weather areas, Dex-Cool degraded faster than the recommended 5 years/150,000 miles, causing early corrosion and water pump and gasket failures.
For some reason, certain engines ran low on coolant without having obvious leaks (can't figure out why). In those cases, if the drivers did not top off the system (because they never checked it, out of trust in the extended life of the coolant), their gasket and water pump seals blew due to overheating.
Dex-Cool is incompatible with other coolants. Engines that got exposed to a mix of different coolants (e.g. flushed dex-cool and filled with green coolant) developed sludge and early corrosion; that is because the flushing procedure was not thorough and residues of old coolant remained in the engine. Needless to say, if you mixed different coolants out right, you were toast.
I'm sure there are other reasons for the controversy surrounding Dex-Cool but I'm just going to ask a few questions for the future in hopes of getting some help from the experts around here. I plan on keeping this car for a long time and don't want to have to sell it at 100K miles! (I kept my Grand AM for 13 years but sold it at 100K miles out of fear of these problems)
Has GM changed the gasket materials to be compatible with Dex-Cool?
Has anyone used the Voltmeter test (http://www.getahelmet.com/jeeps/maint/dexcool/
) or a Refractometer to measure the state of the coolant?
3) My most important question: flushing and filling the system
Regardless of the tests in 2) above, I plan on changing the coolant every 2 years; will it void my warranty
My goal is to thoroughly flush the old coolant out and run distilled water 2-3 times in the system until it comes out clear; then add pure Dex-Cool to the residual distilled water until I get a 50/50 mix; then top off with pre-mixed 50/50 Prestone Dex-Cool. I know that no dealer will put up with this shit so I plan on taking it to my friend who is a mechanic. My question is: how can he run distilled water in the system until it clears out all old coolant??