The coolant used in the cooling system is dex-cool. The engine overheated, so I decided to add more dex-cool. When I opened up the radiator, I noticed this rust-colored dirt-like substance packed inside the radiator. When the dealer that serviced my truck inspected the cooling system, every component had this substance packed in it (water pump, heating core, thermostat, all hoses, radiator, the engine block, etc.). they couldn't clean this substance out of the components and had to replace the whole cooling system. Further inspection of the components of the cooling system shows that they are in perfect working condition other than the substance that can't be removed. The substance isn't rust or corrosion because the components aren't rusted or corroded. This substance, in my opinion, is solidification of the dex-cool coolant. I currently have all of the components that were replaced as well as the substance that still remains inside them. According to the manual of my truck, the cooling system using dex-cool requires no service for 100,000 miles. Previous to this incident, the radiator was never opened. I had only added more dex-cool to the overflow container to maintain the proper coolant level. The dealer where I had my truck serviced had no explanantion as to what has caused this. I contacted GM customer service and they have provided little help and no explanation.

- The Plains, VA, USA