Hey guys, I'm going to flush out the coolant in my system (05 C6) since it says change every 5 years, but I have a few questions if anyone can provide some input. First off, I plan on draining the surge tank, filling with water, letting it run up to operating temp, draining, and repeating. However, my only qualms are that with the pure water I run through the tank that STAYS in the block, how should I know how much Dex-Cool to add in? I know its a 12.6 qt system, but is that ammount of water in the block negligible?

Also, any additives or anything I should run through it to clean it out? Thanks, Kevin

 

I've read that you only need to drain the radiator and refill it. I don't know how true it is.

 

This is true. If you drain the radiator once each year or every other year you never have to flush your radiator. Been doing this for years with all my vehicles and never had a problem. Radiator and cooling system is always clear and clog free. Only takes a few minutes. Be sure to dilute to 50-50 with distilled water and you are good to go.

 

I wouldn't bother with flushing.

Remove the surge tank cap, drain the radiator thru the fitting at the bottom passenger side of the radiator and let it drain.

Buy 6 Quarts of DexCool and 2 gallons of distilled water, close the drain, add the 2 quarts of DexCool, then a gallon of water, then as much DexCool as it will take. Put the cap on the surge tank and run the car until the temp hits 200+°.

Let it cool, then add the remaining DexCool (if any) and enough distilled water to fill. Start the car again, run till the temp gets to 200+°. The surge tank should be to the full line now. You'll have some distilled water left over to top off the radiator if needed.

 

I flushed mine out last summer using Prestone Radiator Flush and distilled water. You want to flush the entire system including the radiator, surge tank, hoses, engine block and heater core, not just the radiator and surge tank. The DexCool extended life coolant is good for about 5 years/100,00 miles so flushing every year sort of defeats the purpose of having the extended life coolant.

When you have the system flushed out and you are ready for the final fill, and the radiator and surge tank are both empty and the radiator drain is closed, add the 6.3 quarts of straight DexCool anti-freeze/coolant first. Now you have the correct amount of anti-freeze/coolant, so the rest of the fill is just water. I used distilled water for the flush and the final fill. Do not use the pre-mixed anti-freeze/coolant because there is water remaining in the engine block, heater core and hoses, therefore, you will not end up with the correct 50/50 mixture.

I kept an eye on the surge tank as over the next couple of weeks as the coolant level would continue to drop as the air was purged out of the system. Again, when the engine is cold, just add (distilled) water to top off the surge tank since you already have the correct amount of anti-freeze/coolant . This way you end up with the recommended 50/50 mixture with no guessing.

 

Watch the price on the pre-mixed DexCool! The 50%/50% is VERY EXPENSIVE compared to straight DexCool and distilled water mixed 50%/50%.

 

I use a simple flush tee installed in a heater hose. Old technology but it allows you to flush the entire system with fresh water from a garden hose in one step and when filling the system with the 6.3 qts of Dexcool as Calemasters instructed the open tee allows the flush water left in the block to be forced out as the new Dexcool is poured in. The open tee while pouring in the new coolant also helps prevent trapped air and assures you can get the full 6.3 qts in.

 

My 05 C6 will be five years old Jan. When changing coolant on my previous Vette the knock sensor on old block when removed drained all the coolant out of the block. A ton of junk was in sides of block. The Lt motor had two knock sensors.
On our new motors I only found one coolant drain plug on right side.
So I plan to drain the block. I have 117,000 + miles. I may even need
a water pump by then. Good winter project.

 

Maybe a stupid question, but could you open the drain valve, put the garden hose in the overflow tank, and the run the engine? Wouldn't it just pump all the coolant out?

 

When I flush the coolant I 1) drain the radiator and 2) remove the engine block coolant drain plug 3) refill with 50/50 mixture. Removing the block plug drains a lot of the block, be sure to torque correctly, 44 lb ft.

If you wait long enough the water pump will need replacing and then flushing is just part of the job, little added effort.

I would not try and flush with a garden hose as the thermostat will get in your way and you are running the water pump without lubricant on the seals. Also I capture the coolant and properly dispose it rather than letting it run to the ocean and I can't capture the amount the garden hose method would create.

 

I don't think so. The cold water from the garden hose would cause the thermostat to close.

 

It should work since the heater hoses are on the "back side" of the thermostat.

 

I screwed up and used premix so I would not need worry about getting the mix right and just found out that premix makes the mix wrong!

Glad the garage is heated....

 

bring the car to the dealer. I don't know what your time is worth, but for $109.00 they flush and fill with new fluid included. It's done right, no problems. They did some other service too.

 

"Done right, no problems" ? Must be the only Dealer in the world that doesn't use their lowest paid lot boy for sloppy, time consuming, no brainer maintenance.

 

That's why the flush tee works so well.
It is not necessary to run the engine during the process and the block and heater core are flushed of all old coolant.
I used to remove block drains etc but its too messy and not necessary with the tee.
The flush machines the dealer has work well but not enough that I would pay the price and trust their hands on the car when I can do it myself for the price of the Dexcool while knowing the job was done right.