subcode1

Had to change ccoolant in my car 2004 C5
1. picked up 8 gallons of distilled water
2.Two gallons Dex Cool straight strength not the 50/50
3. Drained coolant from radiator
4. filled with water
5. ran until temp got to 210 degrees
6. drained.

Did this several time until water draining was clear.
Now I changed my thermostat because it had 50,000 and just in case crap got to it.

Since there was water in the system (about 1 1/2 gallons) I added 6 Quarts of dex cool and a tad more.
Added distilled water to finish. Ran the engine hot again. After cooling checked level and added little more water.

DONE
This brings me to the 50/50 mix real close and eliminated any air in the system.
Checked antifreeze and good for -23 dgrees.

I read a lot of the posts and figured this was about the best method I could come up with. Is it the best ?? I am not the expert but it worked for me. Hope it helps someone.

oh1vette

I think most issues with changing the coolant relate to getting all the air out of the system on refill....

Did you do anything specific to avoid that?

bighank

Drained the radiator and then removed the coolant tank and used the 2 hoses at the bottom to flush coolant out with engine running. Did this till it ran clear. S
Stopped car and let it drain as much as it could and repeated the above. After as much water as possible drained I blew into the hoses and got more water out. Reconnected hoses and closed radiator petcock and slowly added 2 gallons of full strength Dexcool. Added water to fill the coolant tank.
Ran engine with heater on full hot to get any air out of heater lines.
Let it cool overnight. Must have gotten most air out of the system as a month later it shows full. GM doesn't say use distilled water just clean water. Have had dozens of cars and have NEVER used distilled water in the radiator only in lead acid batteries. If you have well water with lots of dissolved minerals maybe distilled water makes sense but if you have clean city tap water I think it is a huge waste.

C5FORFUN2

Distilled water is cheaper than cheap and is easily worth the cost to eliminate the contamination from tap water.

subcode1

"I think most issues with changing the coolant relate to getting all the air out of the system on refill...."

"Did you do anything specific to avoid that?"

As a mechincal engineer for over forty years a review of the cooling system seemed to indicate that this method of flushing only drains fluid in the radiator maintaining the fluid traped at the rest of the motor. That is why I filled and flushed several times getting all the coolant out and having only fresh water and not affecting the fluid level causing air pockets. As for distilled water? at 88 cents a gallon it cannot hurt.
Hope this helps.

wcsinx

No, it won't hurt, but the instant it hits your radiator that water is no longer "distilled". And the difference in dissolved solids/ions in 8 gallons of distilled water v/s tap might amount to one spec of crud in a hose.

2kbluestreak

I made an adapter out of 8" of 2" radiator hose to connect the coolant tank to a garden hose with a couple PVC fittings. A 2" hose clamp at both ends holds the adapter to the tank and the hose fittings on. After catching all the old coolant, which is about 1/2 the systems capacity that will normally drain, I turn on the hose and flush the rest of the system. I shut off the hose and close the drain **** so I can run the engine until the water (now) gets hot enough to open the thermostat so I can turn on the heater. Re-open up the drain **** and turn on the supply water, and I think the whole system gets purged of old coolant mix once the drain water is "clear." I shut off the engine and remove the garden hose adaptera to pour in 4 gallons of condensed water, hoping at best to flush out all the city water, and at least to severly dilute any city water left. Close petcock. The new water in the system is very close to half the system's capacity, so all I have to do is fill up with 100% antifreeze. Running the car afterwards will mix the two liquids close to the ideal 50:50.
The two inch hose adapter on the threads of the coolant tank spout also acts as a "hydraulic fuse" to prevent over pressurizeing the coolant system from my 125 psi city water supply. I could never open the fawct all the way, but have to crack it a little making sure I got a steady stream out of the petcock. A couple times when I opened it too much, the adapter blew off the coolant tank. Normal operating system pressure goverened by the radiator cap, 16 psi, and my line pressure is almost 8 times higher. The procedure takes a couple hours, but could be cut in half if I didn't run the engine up to temperature.

LoneStarFRC

Lots of good ways to get the job done and paying attention to possible entrapped air is always a good thing.

One thing I noticed several people saying is that they ran their heater on full hot/high to help ensure there was no air trapped in the system/lines. Well, since the C5 cooling system has no heater control valve, turning your heater on (to "high" or otherwise) does absolutely nothing to ensure there is no air in the system.

Coolant circulates through your heater core 100% of the time when the engine is running, regardless of where you set your temperature control and/or fan, so turning your temp selector to full hot or the heater on high (fan speed) only accomplishes heating up the interior of your car and nothing else.

In cars/vehicles that have heater control valves that shut off coolant flow when the heater mode is turned off, this would be a good idea, but has no effect on a C5 whatsoever.

HTH

wcsinx

True, many cars do have a heater shut off valve, but the C5 does not.

Though personally I installed one simply because it keeps the cabin a little cooler in the FL summers. I usually close it March and open it back up in November.

LoneStarFRC

That's not an uncommon technique used by many folks over the years in the past. Manual heater control valves are still readily available these days and are pretty cheap too.

baxsom

you have obviously never seen the crap in my water.

there is so much lime in my tap water that I have to CLR the faucets once a month and every time i wash the car it leaves white scale all over the place if i dont dry it soon enough.

wcsinx

Boil away 8 gallons of it and weigh what's left.

Now compare that to the amount of crud built up in your reservoir tank.

You'll be a couple orders of magnitude off.

Just sayin'...