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Help! 2005 C6 Stumped Over Coolant Flush


Oct 22, 2010
Valley Forge, PA
2005 Conv, Z51, 6spd, silver
I decided to do a minor maintenance project today on my 27K miles, 2005, Z51. I've owned this car for almost 4 years and it's due. I have the car on a level 4 post storage lift so it should have been a breeze. Everything I read on many posts said that after opening the radiator plug it should gravity drain 8 of its 12.6 quarts with surge tank fill cap removed. Including the surge tank, I am only able to drain 4 quarts. I applied a small amount of air pressure to the surge tank which gave me a few more drops. I then removed the surge tank and cleaned it with fresh distilled water. I'm stumped. I then added a gallon of distilled water to top off the system and took it for a short drive to open the thermostat and get the water circulated.

This is not going to work as far as I can see. If I can only drain one gallon at a time and continue to drain and heat-up until it runs clear it's going to take a long time waiting for cool down, etc. Also, how can I possibly get the proper 6 gallon DexCool into the system? How do I get that 2 gallons drain?
Last edited:
I think you're trying to put in twice as much as it holds..... 12.6 quarts is a little over 3 gallons total.
Toms - Thanks for the reply. I'm not understanding your comment. I am trying to flush the system. By all accounts, opening the drain plug and surge tank cap should drain 2 gallons of the 3+. I am only getting one. Therefore I am only adding one. Obviously, if 2 gallons were to drain, the remaining gallon + is in the block and heater core. My question is why I am not able to gravity drain two gallons as everyone else seems to do. At the rate I am going I will not be able to totally flush the system and get the appropriate amount of DexCool back into the system.

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