Changed my Dex-Cool today. Used the "drain, fill with 50/50, run engine to circulate coolant" X 3 method. Anyway, I was surprised at the small amount of coolant that drained each time. Got about three quarts, that's all. The filler cap was off, and I even elevated the rear end a bit to see if I could improve the volume. No dice. Each of the three drains produced about three quarts. Is this normal?

 

Sounds like your only getting the water out that is in the radiator. The thermostat may not be opening to allow the water to come out from the block. Next time, after you drain the radiator, remove the thermostat housing, and allow the water to exit the block.

 

I thought about the thermostat issue, but figured it was still hot enough to drain past a partially open thermostat. (steam was coming from the filler opening). Guess I was wrong. I'll try your suggestion next time.

Note... my car is an '02 with 15K on the clock. The coolant has never been changed. It came out clean and clear... couldn't tell it from the new stuff I added.

 

It drains more out when it is level, but you have to use a shallow pan and empty it a lot.

I can drain all but about 2 quarts from mine.

 

There will be some residual left in the heater core as well.

Pull the bottom hose and you might get a little more out of it. Unfortunately, the LSx motors don't have the block drain plugs as did the old sbc and bbc engines of past.

Your local GM dealership should have a device that sucks most of the old stuff out, but it's not inexpensive to do.

 

ok, so what is the best way to drain it?

 

Here is the process I used which I got off the Idaho Corvette Page web site; it is a little time consuming but I feel like the results were worth it. By the way mine was not at all muddy but it was about three years past due when I bought the car (it only had 18k miles on it though)
First I bought about (8) gallons of distilled water (it is cheap, about $1.50 per gallon). The next step is to drain the radiator and then refill it with the distilled water. Run the engine with the heater on until the thermostat opens, shut off the engine, carefully release the pressure in the cooling system and open the radiator drain again. Repeat this procedure until the coolant coming out of the radiator runs clear. I had to do this 4-5 times before mine ran clear. Once the flushing is done, close the drain and fill the system with 6.5 qts. of Dex-Cool (straight Dex-Cool not the 50% mix stuff, the 6.5 qts. will net you the 50% mix you want as the complete system holds about 12-13 qts.) then add distilled water as needed to bring the surge tank up to the recommended fill level. Start the engine and let it idle for a minute then cycle engine speed from idle to 3000 rpm and back until coolant temperature reaches operating temperature and check level again. The coolant level should be about 1/2-in. above the "cold full" mark on the tank. If it is not, top off with distilled water, replace the cap, start the engine and repeat the above procedure.
The most important thing is to be careful when working with hot coolant under pressure!!

 

Excellent advice. I have done it this way myself as well. As you said, distilled (NOT regular, or "drinking" water) is cheap and plentiful at any grocery store.

Btw, one other tip: It is not necessary to run the heater in the car or set the temp selector to "hot". Engine coolant circulates through the heater core at all times, on all C5s. There is no "heater control valve" that shuts off water in the heater hoses like there used to be in the old days (and maybe still used on other vehicles at present). The damper doors inside the HVAC unit assembly is what determines where the blower air gets directed i.e. A/C, heat, etc.

HTH

 

Good to know, I’m from the "old days" and admittedly I have never looked to see if there was a heater control valve or not.

 

Hey, I hear ya on the "old skool". I've dealt with heater control valves for years on the old style cooling systems on many vehicles.

One of the first things I did was buy a factory shop manual when I bought my C5 new back in '99, and come time for a coolant change/flush a few years later, I learned this right away. Turning the heater on or selecting "hot" only gets the inside of the car hot and doesn't "help" anything.