Watchie

Okay, so thirty years ago (maybe more, I don't want to count...) I used to do most of my own auto-maintenance work. Now that I am retired I thought I'd get back to it, starting with a replacement/flush of my 2011 Base C6 coolant system. Having reviewed a good number of threads on this forum I have the following "final" or confirmation questions:

1. How much total will drain from the system? I ask this as my catch-pan holds 10 quarts. Will this be big enough (knowing the system is a bit over 12 quarts but will not fully drain)?

2. Once drained if I want to do a "flush" it is my understanding that I should NOT use a chemical agent (like what Prestone sells) to do this, but just tap water. Is this correct?

3. If just watch do I simply refill, run the car a bit with the heater on, drain and repeat until clear?

4. Any need to remove and clean the overflow tank?

5. I have the Dex-cool (Prestone) and from what I can tell should add about 6.3 quarts, then top off with water so as to get to the 50/50 ratio. This is due to the system holding some residual water after the flush. Correct?

6. Anything I may have missed?

Thanks in advance for any and all input.

cmonkey713

It looks like you have it pretty well covered. One thing, you may need to let the system "Burp" to get any air bubbles out after it is hot and the thermostat open. I know some prefer distilled water instead of tap water for the flush.

C6ToGo

Here is a write-up from another member that i copied over to my service log. Worked for me:

Change coolant every 5 years or 150,000 miles, which ever comes first.
Buy 2 gals Prestone Dex Cool (Walmart) and 6 gals distilled water. I used 5 gals of distilled water this year
and flushed it twice. I think three flushes would have been better.

1) Drain coolant (drain plug is on passenger side). Approx. 8 qts out of 12.6 qts will actually drain.
2) Pull Surge Tank and clean out crud. Refill surge tank to the neck with distilled water.
3) Start engine, idle 4 min
4) Top off surge tank
5) Rev engine at 2000-2500 rpm for 2 more min. (temp should reach ~200 F)
6) Shutoff engine, cool for 20 minutes
7) Repeat steps 1-6 until fluid drains clear (2-4 flushes)
8) Refill with 6.3 qts Dex Cool (it's a slow process) and then top off with distilled water.
9) Repeat steps 3-5, take test drive, refill as necessary with distilled water.
10) Dispose of your old antifreeze at a recycling center.

Watchie

Thanks for the input and guidance.

Gearhead Jim

Getting rid of your drained coolant may be the toughest part of the project.

Although the manual allows using clean tap water for mixing, the lab I used for analysis strongly recommends distilled (not "bottled drinking") water.

If you are going to do multiple drain cycles, you'll want to get the engine warm enough that the thermostat is open each time.

Enjoy!

Watchie

Thanks. My plan is to use tap water for the first flushes, distilled for the last and final fill. As to disposal I'm hoping a local auto repair house will help out. If not, we have periodic recycling drops that will take the old stuff.

Gearhead Jim

That should work, although I used distilled each time because the extra cost was pretty small.

Since most people do just one drain/refill with tap water and no repeats or flushes, and we don't hear of many problems, we shouldn't worry much.

Watchie

Am I correct that no chemical flush should be used?

Gearhead Jim

IIRC, the Owner Manual recommends just a drain and refill, no chemicals and not even a water-only flush is required.

On this Forum, the opinions seem to be strongly opposed to chemical flushes. I have never used any flushing chemicals myself.

ErikR

There's a nice how-to write up here......


https://www.corvetteforum.com/how-to...adiator-368427

outhouse

Just remember to flush with water a few times and know a gallon or so will be left in.


make sure you add two gallons dexcool NOT 50/50 dexcool, then top off with water

geewez

I did all of the above plus the extra step of adding a Prestone flush kit to back flush the cooling system with a garden hose first. You can splice it onto one of the heater hoses that run below the underhood fuse/relay box on the passenger side of the engine compartment.

COvert-red

We purchased a very low-mileage '05 in 2016 and replaced all of the fluids, hoses, rubber, battery, etc. The coolant reservoir was really gummed up and I began the effort of flushing it.... The tank has lots of baffles and I quickly decided to simply replace it. 'Might want to just order a tank in advance - it was about $100.

juanvaldez

Isn't the factory fill 40/60 coolant/water?

hankenstine

I have seen these kits but would never use one because the only way to push the water out of the block is with the thermostat open which means the car must be hot and cold water plus hot engine=blown head gasket or warped heads is this correct???

jft69z

2 gallons is too much. System capacity is 12.6 qts, not 16 qts.

Mix is 50/50.

Midnight08

Midnight08

A greater fill ratio allows for lower cool temp and higher hot temp. I've gone this direction with other cars, since while it may be single digits sitting still, driving at 35-80 mph means the effective temp at the front of the car is much colder. And, on a track day, any extra cooling ceiling is always useful, especially if it turns out to be a really warm one. Just my opinion.

jft69z

At least in the ZR1 and CTS-V communities, guys are going the other way, at least in the intercooler systems. Around 70/30 with water being the 70%. Theory is too much coolant hinders heat transfer. Others go straight water with water wetter, climate conditions being considered (freeze protection in the northern states).

Factory recommends 50/50 as a good mix for temperature protections, corrosion protection & lubrication for waterpump parts.

Gearhead Jim

From what I can read, a 70% Dexcool/30% water mix gives you the most freeze/boil protection. Compared to 50/50 mix, you get a big improvement in freeze temperature but only about a 10' improvement in boil temperature. I've always tried to stay a bit more than 50% Dexcool, but here in the frozen wastelands of northern Illinois, the 50/50 is still fine.

As for heat transfer of water vs Dexcool, I don't know. I'm thinking that if it's an issue, you should really be doing something more than juggling coolant mixtures. But it's an interesting question.